Michael Harmata

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Name: Harmata, Michael

Organization: University of Missouri—Columbia , USA

Department: Department of Chemistry

Title: (PhD)

TOPICS

Organic Chemistry

allene

Chemicals
References

An Asymmetric, Catalytic (4 + 3) Cycloaddition Reaction of Cyclopentenyl Oxyallylic Cations

Co-reporter:Michael Topinka, Kerstin Zawatzky, Charles L. Barnes, Christopher J. Welch, and Michael Harmata

Organic Letters August 4, 2017 Volume 19(Issue 15) pp:

Publication Date(Web):July 25, 2017

DOI:10.1021/acs.orglett.7b01868

Treatment of 2-tosyloxycyclopentanone with substituted furans in the presence of a chiral amino alcohol catalyst and K2HPO4 results in the formation of (4 + 3) cycloaddition products with enantioselectivities that exceed 90% in certain cases.

Comments on a CIP rule conundrum: Why I think I’m right

Co-reporter:Michael Harmata

Tetrahedron Letters 2017 Volume 58, Issue 38(Issue 38) pp:

Publication Date(Web):20 September 2017

DOI:10.1016/j.tetlet.2017.08.010

A question is raised as to how the CIP rules as related to a certain class of 2,1-benzothiazines should be applied. There are two subtle rules among the better known ones that seem to work in opposition, thus creating problems for assignments. It appears that one rule has been give precedence over the other at CAS and in programs like Chemdraw. Whether that is appropriate and true to the original rules is called into question.Download high-res image (50KB)Download full-size image

Electrophilic trapping of α-lithio dienyl sulfones

Co-reporter:Carissa S. Hampton, Michael Harmata

Tetrahedron Letters 2017 Volume 58, Issue 26(Issue 26) pp:

Publication Date(Web):28 June 2017

DOI:10.1016/j.tetlet.2017.05.026

•1-Arylsulfonyl dienes can be easily deprotonated with n-BuLi in THF.•The resulting organolithiums can be easily trapped with electrophiles.•A thioisocyanate gave a mixture of products of two products, one of which was a thiopyran.1-Arylsulfonyl-1,3-dienes may be deprotonated in the presence of a strong base and subsequently trapped by several different electrophilic functional groups.Treatment of a 1-arylsulfonyl diene results in a functionalized organolithium that can be trapped by electrophiles.Download high-res image (31KB)Download full-size image

(4+3) Cycloaddition Reactions of N-Alkyl Oxidopyridinium Ions

Co-reporter:Chencheng Fu;Nestor Lora;Patrick L. Kirchhoefer;Dong Reyoul Lee;Erich Altenhofer;Charles L. Barnes;Dr. Natasha L. Hungerford;Dr. Elizabeth H. Krenske; Dr. Michael Harmata

Angewandte Chemie International Edition 2017 Volume 56(Issue 46) pp:14682-14687

Publication Date(Web):2017/11/13

DOI:10.1002/anie.201708320

AbstractN-Methylation of methyl 5-hydroxynicotinate followed by reaction with a diene in the presence of triethylamine afforded (4+3) cycloadducts in good to excellent yields. High regioselectivity was observed with 1-substituted and 1,2-disubstituted butadienes. Density functional theory calculations indicate that the cycloaddition involves concerted addition of the diene onto the oxidopyridinium ion. The process provides rapid access to bicyclic nitrogenous structures resembling natural alkaloids.

Silver-Catalyzed Cyclization of Sulfonyl Allenes to Dihydrofurans

Co-reporter:Rama Rao Tata and Michael Harmata

Organic Letters 2016 Volume 18(Issue 21) pp:5684-5687

Publication Date(Web):October 27, 2016

DOI:10.1021/acs.orglett.6b02917

Treatment of α-hydroxy allenic sulfones with 10 mol % of silver fluoride in acetonitrile at ambient temperature furnished the corresponding 3-tosyl 2,5-dihydrofurans in excellent yields via a 5-endo-trig cyclization. The starting α-hydroxy allenic sulfones were prepared by lithiation of allenic sulfones and trapping with carbonyl compounds.

Synthesis of Tröger's base derived ligands: PHZ-derivatized ligand with pendant donor arms

Co-reporter:Carissa S. Hampton, Michael Harmata

Tetrahedron 2016 Volume 72(Issue 40) pp:6064-6077

Publication Date(Web):6 October 2016

DOI:10.1016/j.tet.2016.07.056

A cyclic diamine ligand whose core structure was derived from Tröger's base, and included additional pendant arms containing ancillary donor coordination sites was prepared and coordination with transition metals attempted.

Mechanistic Aspects of the Palladium-Catalyzed Isomerization of Allenic Sulfones to 1-Arylsulfonyl 1,3-Dienes

Co-reporter:Carissa S. Hampton and Michael Harmata

The Journal of Organic Chemistry 2016 Volume 81(Issue 11) pp:4807-4822

Publication Date(Web):April 29, 2016

DOI:10.1021/acs.joc.6b00880

When an allenic sulfone is treated under palladium catalysis in the presence of a weak acid, isomerization to a 1-arylsulfonyl 1,3-diene occurs. Investigations of the mechanistic aspects of this isomerization were performed, leading to the mechanism proposed herein. Some further studies of reaction parameters are reported.

[2,3]Sigmatropic Rearrangement of Propargylic Sulfinates by a Pale Ag1-USY Zeolite and Silver Salts

Co-reporter:Carissa S. Hampton

Advanced Synthesis & Catalysis 2015 Volume 357( Issue 2-3) pp:549-552

Publication Date(Web):

DOI:10.1002/adsc.201400978

Radical isomerization of borylated allylic sulfones

Co-reporter:Erich Altenhofer, Michael Harmata

Tetrahedron Letters 2015 Volume 56(Issue 23) pp:3176-3178

Publication Date(Web):3 June 2015

DOI:10.1016/j.tetlet.2014.12.047

We report a preliminary study of the radical isomerization of borylated allylic sulfones to their more thermodynamically stable isomers. This reaction is important as it provides access to structurally unique vinyl boronates not easily accessible by other means.

Suzuki–Miyaura Coupling Reactions of Conjunctive Reagents: 2-Borylated Allylic Sulfones

Co-reporter:Erich F. Altenhofer and Michael Harmata

The Journal of Organic Chemistry 2015 Volume 80(Issue 16) pp:8168-8174

Publication Date(Web):July 31, 2015

DOI:10.1021/acs.joc.5b01253

In support of various efforts in our group, we developed methods for the convenient Suzuki–Miyaura coupling of borylated allylic sulfones with various electrophiles in both inter- and the less common intramolecular modes. The procedure facilitates the preparation of a wide variety of sulfones in a straightforward fashion, including six- through eight-membered rings.

Computational Analysis of the Stereochemical Outcome in the Imidazolidinone-Catalyzed Enantioselective (4 + 3)-Cycloaddition Reaction

Co-reporter:Elizabeth H. Krenske, K. N. Houk, and Michael Harmata

The Journal of Organic Chemistry 2015 Volume 80(Issue 2) pp:744-750

Publication Date(Web):December 19, 2014

DOI:10.1021/jo501906m

Computations show why the catalytic, asymmetric (4 + 3)-cycloaddition reaction developed in the Harmata laboratories proceeds with facial selectivity opposite to that for models proposed for related catalyzed Diels–Alder reactions. Computations with M06-2X/6-311+G(d,p)//B3LYP/6-31G(d) show that iminium ions derived from MacMillan’s chiral 2-tert-butyl-5-benzylimidazolidinone and siloxypentadienals undergo (4 + 3)-cycloadditions with furans preferentially on the more crowded face. Conformational reorganization of the benzyl group, to avoid intramolecular interaction with the silyl group, is responsible for differentiating the activation barriers of top- and bottom-face attack.

A Protocol for the exo-Mono and exo,exo-Bis Functionalization of the Diazocine Ring of Tröger’s Base

Co-reporter:Sami Dawaigher, Kristoffer Månsson, Erhad Ascic, Josep Artacho, Roger Mårtensson, Nagarajan Loganathan, Ola F. Wendt, Michael Harmata, Victor Snieckus, and Kenneth Wärnmark

The Journal of Organic Chemistry 2015 Volume 80(Issue 24) pp:12006-12014

Publication Date(Web):November 24, 2015

DOI:10.1021/acs.joc.5b01921

An efficient protocol has been developed for the exo-mono and exo,exo-bis functionalization of Tröger’s base in the benzylic 6 and 12 positions of the diazocine ring. The lithiation of Tröger’s base using s-BuLi/TMEDA followed by electrophilic quench affords exo-mono- and exo,exo-bis-substituted derivatives of Tröger’s base in good to excellent yields. The variation of the number of equivalents of s-BuLi/TMEDA and the order of addition of the electrophile strongly govern the outcome of the reaction for each electrophile.

A Synthesis of Dihydrofuran-3(2H)-ones

Co-reporter:Rama Rao Tata and Michael Harmata

The Journal of Organic Chemistry 2015 Volume 80(Issue 13) pp:6839-6845

Publication Date(Web):June 11, 2015

DOI:10.1021/acs.joc.5b01076

Treatment of readily available α′-hydroxyenones with a catalytic amount of strong acid in refluxing toluene affords the corresponding dihydrofuran-3(2H)-ones in excellent yields via a formal 5-endo-trig cyclization.

Mechanistic Aspects of the Phosphine-Catalyzed Isomerization of Allenic Sulfones to 2-Arylsulfonyl 1,3-Dienes

Co-reporter:Carissa S. Hampton and Michael Harmata

The Journal of Organic Chemistry 2015 Volume 80(Issue 24) pp:12151-12158

Publication Date(Web):November 2, 2015

DOI:10.1021/acs.joc.5b02097

When an allenic sulfone is treated with a phosphine nucleophile and a proton shuttle, an isomerization to a 2-arylsulfonyl 1,3-diene occurs. Mechanistic aspects of the process were investigated leading to the formulation of a mechanism for the reaction. Some further optimization studies of this process are reported.

Synthesis of Functionalized Cyclic Boronates

Co-reporter:Erich Altenhofer and Michael Harmata

Organic Letters 2014 Volume 16(Issue 1) pp:3-5

Publication Date(Web):December 5, 2013

DOI:10.1021/ol4029918

Deprotonation of a simple borylated allylic sulfone and subsequent alkylation with certain unsaturated electrophiles provide substrates that are easily converted into functionalized alkenyl boronates with ring sizes from five- to seven-membered. A Chan–Lam reaction on one such substrate afforded an alkoxyallylic sulfone that was readily converted via a (4 + 3)-cycloaddition to a polycycle possessing the ABC ring substructure of ingenol.

Regiodivergent Synthesis of 1- and 2-Arylsulfonyl 1,3-Dienes

Co-reporter:Carissa S. Hampton and Michael Harmata

Organic Letters 2014 Volume 16(Issue 4) pp:1256-1259

Publication Date(Web):February 3, 2014

DOI:10.1021/ol500259m

In the course of a study of the alkoxyallylation of allenic sulfones through the use of π-allylpalladium chemistry, we discovered an isomerization of allenic sulfones to arylsulfonyl 1,3-dienes. Under conditions of palladium catalysis in the presence of acids such as acetic acid, allenic sulfones are converted to 1-arylsulfonyl 1,3-dienes. On the other hand, nucleophilic catalysis using triphenylphosphine in the presence of a proton shuttle yields 2-arylsulfonyl 1,3-dienes. Thus, either regioisomer of the arylsulfonyl diene can be prepared at will based on changes in reaction conditions.

Catalytic Generation of Vinylthionium Ions. (4 + 3)-Cycloadditions and Friedel–Crafts Alkylations

Co-reporter:Michael Topinka, Rama Rao Tata, and Michael Harmata

Organic Letters 2014 Volume 16(Issue 17) pp:4476-4479

Publication Date(Web):August 11, 2014

DOI:10.1021/ol502019n

A 3-phenylsulfanyl-substituted allylic alcohol and an ester thereof were treated with Brønsted acids or a gold catalyst, respectively, to generate vinylthionium ions. These species react with dienes, primarily substituted furans, to give products of either (4 + 3)-cycloaddition or Friedel–Crafts alkylation. The results are rationalized on the basis of a stepwise mechanism in which the relative rates of ring closure versus proton loss in the intermediate σ-complex determine the course of the reaction.

A synthesis of 6-deoxy-6-fluorosucrose suitable for PET applications

Co-reporter:Xuefeng Gao, Vikram Gaddam, Michael Harmata

Carbohydrate Research 2014 400() pp: 14-18

Publication Date(Web):5 December 2014

DOI:10.1016/j.carres.2014.08.015

•An efficient synthesis of 6-deoxy-6-fluorosucrose is reported.•Fluorination is both rapid and high-yielding.•The fluorination is designed to be applicable to 18F applications.A new route to 6-deoxy-6-fluorosucrose has been developed. The process proceeds in 8 linear steps in 25% overall yield from sucrose. The steps incorporating fluorine and subsequent deprotection are quite rapid, making the procedure useful in the context of 18F-labeling for PET applications.

New Synthesis of -Hydroxydienones

Co-reporter:Rama Rao Tata;Carissa S. Hampton;Erich F. Altenhofer;Michael Topinka;Weijiang Ying;Xuefeng Gao ;Dr. Michael Harmata

Chemistry - A European Journal 2014 Volume 20( Issue 42) pp:13547-13550

Publication Date(Web):

DOI:10.1002/chem.201404638

Abstract

Herein, attempted oxidation of selected allenols with PCC affording α′-hydroxydienones rather than simple oxidation products is described. The formation of the products observed is rationalized via a series of sigmatropic shifts, followed by hydrolysis.

Chemical Synthesis of 1′-Deoxy-1′-fluorosucrose

Co-reporter:Weijiang Ying, Vikram Gaddam, and Michael Harmata

Organic Letters 2013 Volume 15(Issue 11) pp:2723-2725

Publication Date(Web):May 16, 2013

DOI:10.1021/ol401044h

The first chemical synthesis of 1′-deoxy-1′-fluorosucrose has been accomplished in eight steps from sucrose by an unlikely, but ultimately successful, SN2 displacement reaction.

Generation and alkylation of 2-boryl allylic sulfone anions

Co-reporter:Erich F. Altenhofer and Michael Harmata

Chemical Communications 2013 vol. 49(Issue 23) pp:2365-2367

Publication Date(Web):08 Feb 2013

DOI:10.1039/C3CC00030C

The deprotonation and electrophilic trapping of an allylic sulfone substituted at the 2 position by a pinacol boronate results in the formation of the corresponding alkylation products. The ability of the boronate ester to tolerate the sulfonyl carbanion suggests a broader application of the methodology to prepare a wide range of functionalized boronates.

Benzothiazines in organic synthesis: formation of a cyclopropane via neighboring group participation

Co-reporter:Zhengxin Cai, Michael Harmata

Tetrahedron Letters 2013 Volume 54(Issue 8) pp:814-816

Publication Date(Web):20 February 2013

DOI:10.1016/j.tetlet.2012.11.066

In the course of a synthesis of the antitubercular natural product pseudopteroxazole, we discovered a highly diastereoselective cyclopropanation process. The reaction involved participation of a diene in the departure of a leaving group and could be conducted in high yield after optimization.

Synthesis of 6′-deoxy-6′-fluorosucrose

Co-reporter:Vikram Gaddam, Michael Harmata

Carbohydrate Research 2013 Volume 369() pp:38-41

Publication Date(Web):22 March 2013

DOI:10.1016/j.carres.2012.12.001

A facile synthesis of 6′-deoxy-6′-fluorosucrose has been developed. The title compound is available in six linear steps in 44% overall yield from commercially available sucrose. The synthesis involves rapid and convenient fluorination and deprotection conditions. This procedure would be very useful for the incorporation of radioactive [18F].Graphical abstractHighlights► A synthesis of 6′-deoxy-6′-fluorosucrose is reported. ► A number of different fluorinating agents are useful in this process. ► Fluorination is both rapid and high-yielding, making the process amenable to ‘hot’ chemistry applications.

Formation and ring-opening of 8-oxabicyclo[3.2.1]oct-6-en-3-ones from (4+3)-cycloaddition of furan and chlorocyclopentanone derivatives

Co-reporter:Xuefeng Gao, Michael Harmata

Tetrahedron 2013 69(36) pp: 7675-7682

Publication Date(Web):

DOI:10.1016/j.tet.2013.05.051

Tröger’s Base Twisted Amides: Endo Functionalization and Synthesis of an Inverted Crown Ether

Co-reporter:Josep Artacho, Erhad Ascic, Toni Rantanen, Carl-Johan Wallentin, Sami Dawaigher, Karl-Erik Bergquist, Michael Harmata, Victor Snieckus, and Kenneth Wärnmark

Organic Letters 2012 Volume 14(Issue 18) pp:4706-4709

Publication Date(Web):September 7, 2012

DOI:10.1021/ol302022y

Taking advantage of the unconventional reactivity of twisted mono- and bis-amides of Tröger’s base (TB), rac-6 and rac-7, respectively, the first synthesis of a 6-endo-monosubstituted TB analogue, rac-9, and the first rational synthesis of a 6,12-endo,endo-disubstituted TB analogue, rac-11, have been achieved. The bis-TB crown ether, meso-13, was prepared starting from rac-7. Meso-13 constitutes a rare example of a crown ether with an inverted methylene bridge-to-bridge bis-TB conformation both in solution and in the solid state, resulting in a reluctance to act as a receptor for cations.

Total Synthesis of the Terpenoid Buddledone A: 11-Membered Ring-Closing Metathesis

Co-reporter:Zhengxin Cai, Nattawut Yongpruksa, and Michael Harmata

Organic Letters 2012 Volume 14(Issue 7) pp:1661-1663

Publication Date(Web):March 20, 2012

DOI:10.1021/ol300400x

The first total synthesis of buddledone A was accomplished in seven steps from methyl ethyl ketone (MEK). The key step in the sequence featured an 11-membered ring formation by ring-closing metathesis.

Demethylenation of Trger's Bases with Concomitant Hydrazine Formation

Co-reporter:Xuefeng Gao;Carissa S. Hampton

European Journal of Organic Chemistry 2012 Volume 2012( Issue 36) pp:7053-7056

Publication Date(Web):

DOI:10.1002/ejoc.201201341

Abstract

Trögers bases (TBs) react with dimethyldioxirane to produce the corresponding N-oxides in excellent yields. Upon treatment with acetic anhydride, these N-oxides undergo a Polonovski-type reaction that involves fragmentation and ultimate nitrogen–nitrogen bond formation to form hydrazines. Steric effects are evident in both the oxidation step and in the step involving the activation of the N-oxide, such that certain TBs are not amenable to the process.

Inside Cover: CH Activation in S-Alkenyl Sulfoximines: An Endo 1,5-Hydrogen Migration (Angew. Chem. Int. Ed. 28/2012)

Co-reporter:Xuefeng Gao;Vikram Gaddam;Erich Altenhofer;Rama Rao Tata;Zhengxin Cai;Nattawut Yongpruksa;Aswin K. Garimallaprabhakaran ; Michael Harmata

Angewandte Chemie International Edition 2012 Volume 51( Issue 28) pp:

Publication Date(Web):

DOI:10.1002/anie.201204561

Innentitelbild: CH Activation in S-Alkenyl Sulfoximines: An Endo 1,5-Hydrogen Migration (Angew. Chem. 28/2012)

Co-reporter:Xuefeng Gao;Vikram Gaddam;Erich Altenhofer;Rama Rao Tata;Zhengxin Cai;Nattawut Yongpruksa;Aswin K. Garimallaprabhakaran ; Michael Harmata

Angewandte Chemie 2012 Volume 124( Issue 28) pp:

Publication Date(Web):

DOI:10.1002/ange.201204561

Inside Cover: Twisted Amide Analogues of Trgers Base (Chem. Eur. J. 4/2012)

Co-reporter:Josep Artacho;Erhad Ascic;Dr. Toni Rantanen;Josefine Karlsson;Dr. Carl-Johan Wallentin;Dr. Ruiyao Wang; Ola F. Wendt; Michael Harmata; Victor Snieckus; Kenneth Wärnmark

Chemistry - A European Journal 2012 Volume 18( Issue 4) pp:

Publication Date(Web):

DOI:10.1002/chem.201290009

Twisted Amide Analogues of Trgers Base

Co-reporter:Josep Artacho;Erhad Ascic;Dr. Toni Rantanen;Josefine Karlsson;Dr. Carl-Johan Wallentin;Dr. Ruiyao Wang; Ola F. Wendt; Michael Harmata; Victor Snieckus; Kenneth Wärnmark

Chemistry - A European Journal 2012 Volume 18( Issue 4) pp:1038-1042

Publication Date(Web):

DOI:10.1002/chem.201103228

CH Activation in S-Alkenyl Sulfoximines: An Endo 1,5-Hydrogen Migration

Co-reporter:Xuefeng Gao;Vikram Gaddam;Erich Altenhofer;Rama Rao Tata;Zhengxin Cai;Nattawut Yongpruksa;Aswin K. Garimallaprabhakaran ; Michael Harmata

Angewandte Chemie International Edition 2012 Volume 51( Issue 28) pp:7016-7019

Publication Date(Web):

DOI:10.1002/anie.201203258

CH Activation in S-Alkenyl Sulfoximines: An Endo 1,5-Hydrogen Migration

Co-reporter:Xuefeng Gao;Vikram Gaddam;Erich Altenhofer;Rama Rao Tata;Zhengxin Cai;Nattawut Yongpruksa;Aswin K. Garimallaprabhakaran ; Michael Harmata

Angewandte Chemie 2012 Volume 124( Issue 28) pp:7122-7125

Publication Date(Web):

DOI:10.1002/ange.201203258

Efficient palladium-catalyzed N-arylation of a sulfoximine with aryl chlorides

Co-reporter:Nattawut Yongpruksa, Nathan L. Calkins and Michael Harmata

Chemical Communications 2011 vol. 47(Issue 27) pp:7665-7667

Publication Date(Web):09 Jun 2011

DOI:10.1039/C1CC12444G

The efficient N-arylation of a sulfoximine with aryl chlorides was developed by using Pd2(dba)3 as a catalyst and various ligands. The reactions using RuPhos as a ligand afforded the coupled products in fair to excellent yields.

Benzothiazines in organic synthesis. Synthesis of fluorescent 7-amino-2,1-benzothiazines

Co-reporter:Nattawut Yongpruksa, Siddharth Pandey, Gary A. Baker and Michael Harmata

Organic & Biomolecular Chemistry 2011 vol. 9(Issue 23) pp:7979-7982

Publication Date(Web):11 Aug 2011

DOI:10.1039/C1OB06051A

Fluorescent 7-amino-2,1-benzothiazines were prepared in high yields using the palladium-catalyzed reaction of 4-amino-2-chlorobenzaldehydes with a sulfoximine or the reaction of 7-fluoro-2,1-benzothiazines with amines.

Carbon-to-Carbon Anion Relay Chemistry: Facile Generation of Substituted Allyllithium Species

Co-reporter:Pinguan Zheng;Zhengxin Cai;Aswinkumar Garimallaprabhakaran;Parham Rooshenas;Peter R. Schreiner

European Journal of Organic Chemistry 2011 Volume 2011( Issue 27) pp:5255-5260

Publication Date(Web):

DOI:10.1002/ejoc.201100783

Abstract

Treatment of [2-(2-bromophenyl)allyl]trimethylsilane with tBuLi in THF at –78 °C resulted in the rapid migration of the trimethylsilyl group to afford an allylic organolithium that can be easily trapped by a wide range of electrophiles. This is a rare example of a synthetically useful and efficientcarbon-to-carbon migration of a silicon group and represents a new approach to allylic organolithium species using anion relay chemistry.

Carbon-to-Carbon Anion Relay Chemistry: Facile Generation of Substituted Allyllithium Species (Eur. J. Org. Chem. 27/2011)

Co-reporter:Pinguan Zheng;Zhengxin Cai;Aswinkumar Garimallaprabhakaran;Parham Rooshenas;Peter R. Schreiner

European Journal of Organic Chemistry 2011 Volume 2011( Issue 27) pp:

Publication Date(Web):

DOI:10.1002/ejoc.201190072

Abstract

The cover picture shows Columbia, Missouri's Activity & Recreation Center, whose acronym, ARC, fits perfectly with Anion Relay Chemistry, details of which are discussed in the article by P. R. Schreiner, M. Harmata et al. on p. 5255 ff. The cover was designed and assembled by Professor Harmata, and certain graphics were improved by Ms. Tammy McNiel.

Benzothiazines in organic synthesis. An approach to floresolide B

Co-reporter:Yugang Chen, Michael Harmata

Tetrahedron Letters 2011 Volume 52(Issue 32) pp:4069-4071

Publication Date(Web):10 August 2011

DOI:10.1016/j.tetlet.2011.05.091

The intramolecular conjugate addition of a sulfoximine carbanion to an α,β-unsaturated ester results in the formation of a benzothiaine bearing a benzylic stereocenter with extremely high fidelity. We have used this methodology to complete a formal total synthesis of the antitumor agent (+)-floresolide B.

Toward the total synthesis of elisapterosin B: a Hg(OTf)2-promoted diastereoselective intramolecular Friedel–Crafts alkylation reaction

Co-reporter:Weijiang Ying, Charles L. Barnes, Michael Harmata

Tetrahedron Letters 2011 Volume 52(Issue 2) pp:177-180

Publication Date(Web):12 January 2011

DOI:10.1016/j.tetlet.2010.10.109

As part of an approach to the synthesis of the antitubercular agent elisapterosin B, we prepared two different chiral, non-racemic olefinic substrates and examined their diastereoselective ring closure using mercury salts. The effort yielded potential precursors to elisapterosin B in good yield with good to excellent diastereocontrol.

Oxidation of 4-methoxyanilines to 1,4-benzoquinones using ceric ammonium nitrate (CAN)

Co-reporter:Yugang Chen, Weijiang Ying, Michael Harmata

Tetrahedron Letters 2011 Volume 52(Issue 4) pp:480-482

Publication Date(Web):26 January 2011

DOI:10.1016/j.tetlet.2010.11.070

Treatment of substituted 4-methoxyanilines with ceric ammonium nitrate in a 1:1 mixture of water and acetonitrile resulted in the formation of 1,4-benzoquinones in acceptable yields.

Studies Directed toward the Synthesis of Hamigeran B: A Catalytic Oxidative Cyclization

Co-reporter:Zhengxin Cai and Michael Harmata

Organic Letters 2010 Volume 12(Issue 24) pp:5668-5670

Publication Date(Web):November 16, 2010

DOI:10.1021/ol102478h

An approach to the synthesis of hamigeran B is described. Key steps include a Tius−Nazarov cyclization and a palladium-catalyzed oxidative cyclization of an α-hydroxyenone.

The (4+3)-cycloaddition reaction: heteroatom-substituted allylic cations as dienophiles

Co-reporter:Michael Harmata

Chemical Communications 2010 vol. 46(Issue 47) pp:8904-8922

Publication Date(Web):10 Nov 2010

DOI:10.1039/C0CC03621H

The (4+3)-cycloaddition of allylic cations to dienes is a powerful method for the direct synthesis of seven-membered rings. Recent developments in this area have included new methods for the generation of allylic cations, diastereoselective and catalytic, enantioselective reactions, an increased understanding of the diverse mechanistic possibilities of the reaction and applications to the total synthesis of natural products and their analogues.

Origin of Stereoselectivity in the (4 + 3) Cycloadditions of Chiral Alkoxy Siloxyallyl Cations with Furan

Co-reporter:Elizabeth H. Krenske, K. N. Houk and Michael Harmata

Organic Letters 2010 Volume 12(Issue 3) pp:444-447

Publication Date(Web):January 11, 2010

DOI:10.1021/ol902591k

The mechanisms and stereoselectivities of (4 + 3) cycloadditions between chiral alkoxy siloxyallyl cations and furan are examined using density functional theory calculations. These cycloadditions are predicted to take place via stepwise mechanisms. The stereoselectivities of cycloadditions involving siloxyallyl cations derived from chiral α-methyl benzylic alcohols are controlled by two effects: minimization of steric repulsion between the α-Me group and the allyl group and attractive CH−π interactions between the furan and the aryl group.

The (4+3)-cycloaddition reaction: simple allylic cations as dienophiles

Co-reporter:Michael Harmata

Chemical Communications 2010 vol. 46(Issue 47) pp:8886-8903

Publication Date(Web):08 Nov 2010

DOI:10.1039/C0CC03620J

Benzothiazines in synthesis. Eight-membered ring formation in an intramolecular Friedel–Crafts reaction

Co-reporter:Michael Harmata, Weijiang Ying, Charles L. Barnes

Tetrahedron Letters 2009 50(20) pp: 2326-2328

Publication Date(Web):

DOI:10.1016/j.tetlet.2009.02.227

Benzothiazines in Synthesis. Further Studies of the Intramolecular, Stereoselective Addition of Sulfonimidoyl Carbanions to α,β-Unsaturated Functional Groups

Co-reporter:Michael Harmata, Kanok-on Rayanil, Vinson R. Espejo and Charles L. Barnes

The Journal of Organic Chemistry 2009 Volume 74(Issue 8) pp:3214-3216

Publication Date(Web):March 13, 2009

DOI:10.1021/jo900151d

A variety of alkenes substituted by electron-withdrawing groups serve as competent electrophiles for the stereoselective, intramolecular nucleophilic addition of sulfonimidoyl carbanions to form benzothiazines. This reaction generally proceeds with complete stereoselectivity within the limits of our detection. In some cases, benzothiazine formation occurs in a single pot at relatively high temperatures during N-arylation of the simple sulfoximine used in this study. Yet, the process occurs with the same direction and extent of stereoselectivity as that seen when the Michael addition is performed at very low temperatures.

A gold-catalyzed [4+3]-cycloaddition of functionalized dioxines

Co-reporter:Michael Harmata, Chaofeng Huang

Tetrahedron Letters 2009 50(41) pp: 5701-5703

Publication Date(Web):

DOI:10.1016/j.tetlet.2009.07.111

A rigid GABA analog from a [4+3]-cycloaddition

Co-reporter:Paitoon Rashatasakhon, Michael Harmata

Tetrahedron Letters 2009 50(18) pp: 2109-2110

Publication Date(Web):

DOI:10.1016/j.tetlet.2009.02.113

Silver-Catalyzed Rearrangement of Propargylic Sulfinates to Allenic Sulfones

Co-reporter:Michael Harmata ;Chaofeng Huang

Advanced Synthesis & Catalysis 2008 Volume 350( Issue 7-8) pp:972-974

Publication Date(Web):

DOI:10.1002/adsc.200700447

Abstract

Treatment of propargylic sulfinate esters with 2 mol % of silver hexafluoroantimonate results in the rapid formation of allenic sulfones in essentially quantitative yield.

Inside Cover: An Interrupted [4+3] Cycloaddition Reaction: A Hydride Shift (Ene Reaction) Intervenes (Angew. Chem. Int. Ed. 45/2008)

Co-reporter:Michael Harmata ;Chaofeng Huang;Parham Rooshenas Dr.;PeterR. Schreiner Dr.

Angewandte Chemie International Edition 2008 Volume 47( Issue 45) pp:

Publication Date(Web):

DOI:10.1002/anie.200890229

An Interrupted [4+3] Cycloaddition Reaction: A Hydride Shift (Ene Reaction) Intervenes

Co-reporter:Michael Harmata ;Chaofeng Huang;Parham Rooshenas Dr.;PeterR. Schreiner Dr.

Angewandte Chemie International Edition 2008 Volume 47( Issue 45) pp:8696-8699

Publication Date(Web):

DOI:10.1002/anie.200803487

An Interrupted [4+3] Cycloaddition Reaction: A Hydride Shift (Ene Reaction) Intervenes

Co-reporter:Michael Harmata ;Chaofeng Huang;Parham Rooshenas Dr.;PeterR. Schreiner Dr.

Angewandte Chemie 2008 Volume 120( Issue 45) pp:8824-8827

Publication Date(Web):

DOI:10.1002/ange.200803487

Innentitelbild: An Interrupted [4+3] Cycloaddition Reaction: A Hydride Shift (Ene Reaction) Intervenes (Angew. Chem. 45/2008)

Co-reporter:Michael Harmata ;Chaofeng Huang;Parham Rooshenas Dr.;PeterR. Schreiner Dr.

Angewandte Chemie 2008 Volume 120( Issue 45) pp:

Publication Date(Web):

DOI:10.1002/ange.200890278

Asymmetric Catalytic [4+3] Cycloaddition Reactions

Co-reporter:Michael Harmata

Advanced Synthesis & Catalysis 2006 Volume 348(Issue 16-17) pp:

Publication Date(Web):27 NOV 2006

DOI:10.1002/adsc.200600294

Although the [4+3] cycloaddition reaction has seen considerable attention over the past 10–15 years, only a few investigations have been dedicated to the development of a catalytic, asymmetric process. This short review covers some of the advances made in the area of absolute stereocontrol in this higher order cycloaddition and will hopefully serve as an inspiration towards the development of asymmetric, catalytic versions of the reaction.

Intermolecular [4+2] Cycloadditions of a Reactive Cyclopentadienone

Co-reporter:Michael Harmata;Maria G. Gomes

European Journal of Organic Chemistry 2006 Volume 2006(Issue 10) pp:

Publication Date(Web):31 MAR 2006

DOI:10.1002/ejoc.200600173

A reactive cyclopentadienone gives Diels–Alder cycloadducts with a variety of dienes in high yield and often with extremely high levels of regio- and stereoselectivity. The high degree of generality of this reaction suggests it will be of use in organic synthesis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Deantiaromatization as a Driving Force in an Electrocyclic Reaction

Co-reporter:Michael Harmata ;Pinguan Zheng;Peter R. Schreiner Dr.;Armo Navarro-Vázquez Dr.

Angewandte Chemie 2006 Volume 118(Issue 12) pp:

Publication Date(Web):22 FEB 2006

DOI:10.1002/ange.200503812

Starker Antrieb: Theorie und Experiment stützen die Annahme, dass „Desantiaromatisierung“ die Triebkraft in der 8-π-Elektronen-Elektrocyclisierung eines Cyclopentadienons sein könnte (siehe Schema; TEA: Triethylamin, TFE: Trifluorethanol). Die Reaktion verläuft mit präparativ nützlichen Ausbeuten und könnte zur Synthese des Virostatikums Hamigeran B genutzt werden.

Deantiaromatization as a Driving Force in an Electrocyclic Reaction

Co-reporter:Michael Harmata, Pinguan Zheng, Peter R. Schreiner,Armando Navarro-Vázquez

Angewandte Chemie International Edition 2006 45(12) pp:1966-1971

Publication Date(Web):

DOI:10.1002/anie.200503812

Substitution of a bridgehead bromide by primary organolithium reagents

Co-reporter:Michael Harmata and Sumrit Wacharasindhu

Chemical Communications 2003 (Issue 19) pp:2492-2493

Publication Date(Web):20 Aug 2003

DOI:10.1039/B308112E

The reaction of ketone 1 with primary organolithium reagents in THF/HMPA affords not the expected carbonyl addition product but the product of bromide substitution, in reasonable yield.

Crystal structure of a chiral, copper(I) complex of styrene

Co-reporter:Michael Harmata, Sunil K Ghosh, Charles L Barnes

Journal of Supramolecular Chemistry 2002 Volume 2(1–3) pp:349-351

Publication Date(Web):January–June 2002

DOI:10.1016/S1472-7862(02)00027-8

The crystal structure of a copper(I) complex of styrene in the presence of a chiral, nonracemic bisbenzothiazine ligand has been determined. Comparisons are made between similar crystal structures reported in the literature.Graphic

A One-Pot, One-Operation [3+3] Annulation Approach to Benzothiazines

Co-reporter:Michael Harmata;Neville Pavri

Angewandte Chemie International Edition 1999 Volume 38(Issue 16) pp:

Publication Date(Web):6 AUG 1999

DOI:10.1002/(SICI)1521-3773(19990816)38:16<2419::AID-ANIE2419>3.0.CO;2-I

Enantiomerically pure 2,1-benzothiazines are readily prepared by a one-pot, one-operation procedure consisting of a palladium-catalyzed aryl amination of an ortho-bromobenzaldehyde with a sulfoximine followed by an intramolecular condensation reaction [Eq. (1)]. BINAP=1,1′-binaphthalene-2,2′-diylbis(diphenylphosphane).

Herstellung von Benzothiazinen durch [3+3]-Anellierung in einer Eintopfreaktion und in einem Arbeitsgang

Co-reporter:Michael Harmata;Neville Pavri

Angewandte Chemie 1999 Volume 111(Issue 16) pp:

Publication Date(Web):6 AUG 1999

DOI:10.1002/(SICI)1521-3757(19990816)111:16<2577::AID-ANGE2577>3.0.CO;2-N

Enantiomerenreine 2,1-Benzothiazine lassen sich leicht durch palladiumkatalysierte Arylaminierung eines ortho-Brombenzaldehyds mit einem Sulfoximin und anschließende intramolekulare Kondensation herstellen [Gl. (1)]. Das Verfahren kann in einem einzigen Arbeitsgang und als Eintopfverfahren durchgeführt werden. BINAP = 1,1′-Binaphthalin-2,2′-diylbis(diphenylphosphan).

The (4+3)-cycloaddition reaction: heteroatom-substituted allylic cations as dienophiles

Co-reporter:Michael Harmata

Chemical Communications 2010 - vol. 46(Issue 47) pp:NaN8922-8922

Publication Date(Web):2010/11/10

DOI:10.1039/C0CC03621H

The (4+3)-cycloaddition reaction: simple allylic cations as dienophiles

Co-reporter:Michael Harmata

Chemical Communications 2010 - vol. 46(Issue 47) pp:NaN8903-8903

Publication Date(Web):2010/11/08

DOI:10.1039/C0CC03620J

Generation and alkylation of 2-boryl allylic sulfone anions

Co-reporter:Erich F. Altenhofer and Michael Harmata