In this paper, a novel compound 3-(2-quinolyl)-5-ferrocenyl-isoxazole(5) with high selectivity toward Cu2+ over other heavy and transition-metal(HTM) ions was designed and synthesized in good yields. The compound not only could be used as an electrochemical probe for Cu2+ with an anodic peak shift of Fe(II)/Fe(III) redox couple, but also could be a colorimetric and fluorescent probe due to the detectable change in color by naked eyes and a significant fluorescence quenching of monomeric anthracene moiety. This highly selective sensing of Cu2+ may be attributed to the unprecedented intermolecular electron-transfer reorganization after the oxidation of the first single electron of compound 5, as indicated by electrospray ionization mass spectrometry(ESI-MS) and density functional theory(DFT) calculation results. To the best of our knowledge, this class of compounds have rarely been reported in the field of molecular sensing. It may have a potential significance for the application of the ferrocenyl-isoxazole derivative in molecular recognition.

A mild and efficient Rh(III)-catalyzed C–H activation/esterification reaction for the synthesis of isocoumarins has been developed. This procedure uses readily available benzoic acids and cyclic diazo-1,3-diketones as starting materials and involves domino intermolecular C–H activation in combination with intramolecular esterification to give the corresponding isocoumarins in moderate to excellent yields. This process provides a facile approach for the construction of isocoumarins containing various functional groups that does not require any additives.

A novel and efficient strategy for the synthesis of 2-hydroxy-6-oxocyclohex-1-enecarboxamides through a Rh2(OAc)4-catalyzed direct carboxamidation of cyclic 2-diazo-1,3-diketones has been developed. The method features readily available starting materials, easy scalability, mild reaction conditions and a simple work-up for product isolation, which makes this strategy highly attractive. A tentative mechanism involving an isocyanide insertion and hydrolysis sequence for this reaction is proposed.

A one-pot domino reaction involving Lewis acid-mediated nucleophilic-substitution/intramolecular-cyclization/reverse Claisen condensation of 2-(aryl(piperidin-1-yl)methyl)phenols and 1,3-diketones has been developed for the synthesis of 2-(3-oxo-1-phenylbutyl)phenyl acetates in good to excellent yields (77%–95%). The construction of the products has been accomplished via the domino generation of two new σ-bonds (CC and CO) with a wide functional group tolerance by using FeCl3 as mediation.Download high-res image (214KB)Download full-size image

A highly enantioselective 1,3-dipolar cycloaddition of imino esters with methyleneindolinones has been realized by using readily available thiourea–quaternary ammonium salts as phase-transfer catalysts, enabling efficient construction of a range of chiral spiro[pyrrolidin-3,3′-oxindoles] in good yields with excellent enantioselectivities under mild conditions.

Reported here is a convenient catalyst-free method for preparing a series of spiro[indoline-3,2′-pyrroles] from a three-component reaction of isatins, α-amino acid and phenylpropiolic acid esters in refluxing isopropanol with high regioselectivity and yields. A plausible mechanism for this process was proposed. In addition, this protocol permitted the facile construction of spiro[indoline-3,2′-pyrroles] through an expanded scope of substrates.

An efficient, environmentally friendly and one-pot route to new 9-aryl/9-arylethynyl-2,3,4,9-tetrahydro-1H-xanthen-1-one derivatives from inexpensive starting materials has been developed. This method proceeded by a domino nucleophilic-substitution/intramolecular cyclization/dehydration sequence of propargylic amines/diaryl amines and 1,3-cyclohexanediones under the promotion of FeCl3, which involved the formation of two new σ (C–C and C–O) bonds in a single operation for the construction of novel tetrahydroxanthene skeletons in 68–95% yields.

A convenient and efficient method was developed for the synthesis of naphtho[2,1-b]furans via 4-dimethylaminopyridine(DMAP)-catalyzed cascade reaction of 2-hydroxy-1-naphthaldehydes and α-halogenated ketones in moderate to good yields in the presence of Na2CO3 at 80 ºC for 6 h. The mechanism for this process was briefly discussed with a tentative catalytic cycle proposed. Moreover, this method features organocatalysts and high step-economy, which make it practical and attractive.

The enantioselective construction of five-membered spirocyclic oxindoles via a double Michael cascade reaction is described by using dipeptide-based multifunctional quaternary phosphonium salt catalysts. The desired products were obtained in excellent yields (up to 94%) and good to high stereoselectivities (up to >19:1 dr and 99% ee).

The synthesis of β-alkynyl ketones was achieved in good to excellent yields by an iron-catalyzed domino reaction of N-cyclohexyl propargylamines and 1,3-diketones. A plausible mechanism involving nucleophilic substitution, intramolecular cyclization, and reverse Claisen condensation for this process is proposed.

Desymmetrization of meso-aziridines with aromatic thiols was realized by using α-amino acids-derived chiral quaternary phosphonium salts catalysts to provide chiral β-amino sulfides with high yields (up to 99%) and in moderate enantioselectivities (up to 70%).

A FeCl3-catalyzed multicomponent reaction was developed for the facile synthesis of coumarin-3-carboxylic ester derivatives in a highly atom-economic and environmentally friendly way. Using simple and cheaply available salicylaldehydes, Meldrum's acid and alcohols as the starting materials, the method needs no extra additives and features wide substrate scope, good functional group tolerance and mild reaction conditions.

An asymmetric Michael addition of α-cyanoketones to α,β-unsaturated aldehydes to form chiral dihydropyrans catalyzed by l-diphenylprolinol trimethylsilyl ether is presented. A series of 3,4-dihydropyrans were obtained in excellent yields (up to 91%) and enantioselectivities (up to 98% ee). A plausible mechanism for this process is proposed.(4S)-6-(4-Bromophenyl)-2-hydroxy-4-phenyl-3,4-dihydro-2H-pyran-5-carbonitrileC18H14BrNO2[α]D30 = +22.6 (c 1.30, CHCl3)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)(4S)-6-(4-Bromophenyl)-2-hydroxy-4-(p-tolyl)-3,4-dihydro-2H-pyran-5-carbonitrileC19H16BrNO2[α]D24 = +4.6 (c 0.85, CHCl3)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)(4S)-6-(4-Bromophenyl)-2-hydroxy-4-(4-methoxyphenyl)-3,4-dihydro-2H-pyran-5-carbonitrileC19H16BrNO3[α]D30 = +13.5 (c 1.25, CHCl3)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)(4S)-6-(4-Bromophenyl)-2-hydroxy-4-(2-methoxyphenyl)-3,4-dihydro-2H-pyran-5-carbonitrileC19H16NO3Br[α]D30 = −1.0 (c 1.20, CHCl3)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)(4S)-6-(4-Bromophenyl)-4-(4-chlorophenyl)-2-hydroxy-3,4-dihydro-2H-pyran-5-carbonitrileC18H12BrClNO2[α]D24 = +13.7 (c 1.80, CHCl3)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)(4S)-4,6-Bis(4-bromophenyl)-2-hydroxy-3,4-dihydro-2H-pyran-5-carbonitrileC18H12Br2NO2[α]D30 = +8.7 (c 1.75, CHCl3)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)(4R)-6-(4-Bromophenyl)-2-hydroxy-4-methyl-3,4-dihydro-2H-pyran-5-carbonitrileC13H12BrNO2[α]D30 = +37.5 (c 1.00, CHCl3)Source of chirality: Asymmetric catalysisAbsolute configuration: (R)(4R)-6-(4-Bromophenyl)-4-(furan-2-yl)-2-hydroxy-3,4-dihydro-2H-pyran-5-carbonitrileC16H12BrNO3[α]D24 = +57.1 (c 1.10, CHCl3)Source of chirality: Asymmetric catalysisAbsolute configuration: (R)(4S)-6-(4-Bromophenyl)-2-hydroxy-4-(4-methoxyphenyl)-3,4-dihydro-2H-pyran-5-carbonitrileC18H15NO2[α]D30 = +31.0 (c 1.05, DMSO)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)(4S)-6-(2-Bromophenyl)-2-hydroxy-4-phenyl-3,4-dihydro-2H-pyran-5-carbonitrileC18H14NO2Br[α]D30 = +59.0 (c 1.10, MeOH)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)(4S)-6-(3-Bromophenyl)-2-hydroxy-4-phenyl-3,4-dihydro-2H-pyran-5-carbonitrileC18H14NO2Br[α]D24 = +31.3 (c 1.60, CHCl3)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)(4S)-2-Hydroxy-4-phenyl-6-(p-tolyl)-3,4-dihydro-2H-pyran-5-carbonitrileC19H17NO2[α]D30 = +22.6 (c 0.75, CHCl3)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)(4S)-2-Hydroxy-6-(4-methoxyphenyl)-4-phenyl-3,4-dihydro-2H-pyran-5-carbonitrileC19H17NO3[α]D30 = −20.0 (c 1.20, MeOH)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)(4S)-6-(4-Fluorophenyl)-2-hydroxy-4-phenyl-3,4-dihydro-2H-pyran-5-carbonitrileC18H14FNO2[α]D24 = +8.1 (c 1.05, MeOH)Source of chirality: Asymmetric catalysisAbsolute configuration: (S)

We report an efficient route to pyridine derivatives via an FeCl3-catalyzed four-component nucleophilic addition/intermolecular cyclization. This simple fragment assembly strategy uses mild conditions and affords a broad range of polysubstituted pyridines in moderate to good yield from simple and readily available starting materials. A plausible mechanism for this process is proposed.

A series of 3,4-dihydro-2H-1,4-benzo[b]thiazines (34 examples) were efficiently synthesized in good to excellent yields through a 1,4-diazabibicyclo[2.2.2]octane (DABCO) catalyzed one-pot, three-component reaction of 2-aminobenzenethiol, aromatic aldehydes and α-halogenated ketones in the presence of K2CO3. The mechanism for this process was briefly discussed with a tentative catalytic cycle proposed.

A straightforward synthesis of pyrrolo[2,1-a]isoquinolines has been achieved from 1,3-dipolar cycloaddition reaction between isoquinoliniums and alkynes in the presence of K2CO3, and features with versatility, easy operation and mild reaction conditions. 22 examples were synthesized.

A facile and efficient synthesis of N-sulfonyl-N,N-disubstituted amidines has been achieved via a CuI-catalyzed three-component free-radical coupling reaction of tertiary amines and arenesulfonyl azides with terminal alkynes in the presence of azodiisobutyronitrile (AIBN). The reaction mechanism of this reaction has also been studied.