Lithiooxiranes [LiCR¹(O)CR²R³, R¹ = H, Me; R²/R³ = H/Ph, H/tBu, Me/Ph], generated by sulfoxide–lithium exchange from stereodefined sulfinyl epoxides (with use of PhLi or tBuLi, THF, at or below –90 °C), were employed for the stereospecific reagent-controlled homologation of boronic esters R⁰–Bpin (R⁰ = BnCH₂, allyl, cHex, Ph). Addition of TBSOTf to the intermediate ate complexes gave β-silyloxyboronates that were converted to vicinal diol monosilyl ethers by oxidative work-up with aq. NaOOH. The 2°/2° (4–32 %, dr > 98:2), 2°/3° (21–66 %, dr ≥ 65:35), and 3°/3° (59–68 %, dr ≥ 95:5) contiguous stereodiad-containing compounds created in this manner were typically obtained in a highly stereocontrolled manner. In general, cis-sulfinyl epoxides afforded anti-like stereodiads, whereas trans-sulfinyl epoxides afforded syn-like stereodiads; however, as a result of its suspected configurational instability, LiCMe(O)CHPh gave anti-like 2°/3° motifs regardless of sulfinyl epoxide stereochemistry.

The entitled monohydrolysis products, also known as α-ethylhexyl and β-ethylhexyl sulfosuccinate (EHSS), of the surfactant diisooctyl sulfosuccinate (DOSS) were synthesized in stable isotope-labelled form from [¹³C]₄-maleic anhydride. Sodium [¹³C]₄-1-carboxy-2-(2-ethylhexyloxycarbonyl)ethanesulfonate (α-EHSS) was prepared by the method of Larpent by reaction of 2-ethylhexan-1-ol with [¹³C]₄-maleic anhydride followed by regioselective conjugate addition of sodium bisulfite to the resulting monoester (38% overall yield). The regiochemical outcome of bisulfite addition was confirmed by a combination of ¹³C/¹³C (incredible natural abundance double quantum transfer) and ¹H/¹³C (heteronuclear multiple-bond correlation (HMBC)) NMR spectral correlation experiments. Sodium [¹³C]₄-2-carboxy-1-(2-ethylhexyloxycarbonyl)ethanesulfonate (β-EHSS) was prepared in four steps by reaction of 4-methoxybenzyl alcohol with [¹³C]₄-maleic anhydride, regioselective sodium bisulfite addition, N,N′-dicyclohexylcarbodiimide-mediated esterification with 2-ethylhexan-1-ol, and p-methoxybenzyl ester deprotection with trifluoroacetic acid (13% overall yield). The regiochemical outcome of the second synthesis was confirmed by a combination of ¹J_CC scalar coupling constant analysis and ¹H/¹³C (HMBC) NMR spectral correlation. The materials prepared are required as internal standards for the liquid chromatography–mass spectrometry (LC-MS)/MS trace analysis of the degradation products of DOSS, the anionic surfactant found in Corexit, the oil dispersant used during emergency response efforts connected to the Deepwater Horizon oil spill of April 2010. Copyright © 2014 John Wiley & Sons, Ltd.

Four putative functionalized α-chloroakyllithiums RCH₂CHLiCl, where R=CHCH₂ (18 a), CCH (18 b), CH₂OBn (18 c), and CH[O(CH₂)₂O] (18 d), were generated in situ by sulfoxide–lithium exchange from α-chlorosulfoxides, and investigated for the stereospecific reagent-controlled homologation (StReCH) of phenethyl and 2-chloropyrid-5-yl (17) pinacol boronic esters. Deuterium labeling experiments revealed that α-chloroalkyllithiums are quenched by proton transfer from their α-chlorosulfoxide precursors and it was established that this effect compromises the yield of StReCH reactions. Use of α-deuterated α-chlorosulfoxides was discovered to ameliorate the problem by retarding the rate of acid-base chemistry between the carbenoid and its precursor. Carbenoids 18 a and 18 b showed poor StReCH efficacy, particularly the propargyl group bearing carbenoid 18 b, the instability of which was attributed to a facile 1,2-hydride shift. By contrast, 18 d, a carbenoid that benefits from a stabilizing interaction between O and Li atoms gave good StReCH yields. Boronate 17 was chain extended by carbenoids 18 a, 18 b, and 18 d in 16, 0, and 68 % yield, respectively; α-deuterated isotopomers D-18 a and D-18 d gave yields of 33 and 79 % for the same reaction. Double StReCH of 17 was pursued to target contiguous stereodiads appropriate for the total synthesis of (−)-epibatidine (15). One-pot double StReCH of boronate 17 by two exposures to (S)-D-18 a (≤66 % ee), followed by work-up with KOOH, gave the expected stereodiad product in 16 % yield (d.r.∼67:33). The comparable reaction using two exposures to (S)-D-18 d (≤90 % ee) delivered the expected bisacetal containing stereodiad (R,R)-DD-48 in 40 % yield (≥98 % ee, d.r.=85:15). Double StReCH of 17 using (S)-D-18 d (≤90 % ee) followed by (R)-D-18 d (≤90 % ee) likewise gave (R,S)-DD-48 in 49 % yield (≥97 % ee, d.r.=79:21). (R,S)-DD-48 was converted to a dideuterated isotopomer of a synthetic intermediate in Corey’s synthesis of 15.

6,6′-Bis(methylaminosulfonyl)-7,7′-dihydroxy-8,8′-biquinolyl (3) catalyzes (5–10 mol-%) the addition of trimethylsilyl cyanide to aldehydes (aryl, alkyl, and α,β-unsaturated; 42–92 % yields), ketones (aryl alkyl, dialkyl; 22–82 % yields), and N-benzylaldimines (14–78 % yields) in toluene (0 °C or room temp.) to give the expected cyanohydrin and Strecker adducts following desilylation. Among a series of closely related compounds lacking any one of their defining structural features, bis-sulfonamide 3 and its N,N′-dimethyl derivative are exceptional in catalyzing the silylcyanation of benzaldehyde in the absence of all other additives. Hammett analysis of the competitive silylcyanation of para-substituted benzaldehydes catalyzed by 3 showed a linear free-energy relationship (R² = 0.928) with a modest positive reaction constant (ρ = +1.52). X-ray diffraction analysis of (±)-3 indicated a cisoid biaryl conformation and the existence of an intramolecular hydrogen bond between C7′–OH and C7–O. Resolution of (±)-3 was achieved by HPLC separation of its tetravalerate derivative on a chiral stationary phase. The absolute configurations of the optical isomers of 3 were assigned by correlation of the ECD spectra with those of related biquinolyls of known configuration. The silylcyanation of aldehydes catalyzed by (–)-(aR)-3 leads to cyanohydrins with a preference for the (S)-configured product with an ee of <10 %. The organocatalytic action of 3 is ascribed to hydrogen bonding and Brønsted acid catalysis effects that are dependent on its acidifying sulfonamide groups, general base capability, and interannular proximity effects made possible by the biaryl structure.