Silicon- and tin-directed oxidative decarboxylation: regioselective formation of olefins from β-silyl and β-stannyl carboxylic acids

Formation of Enol Ethers by Radical Decarboxylation of α-Alkoxy β-Phenylthio Acids

“…The plan (Scheme ) was to effect conjugate addition of a PhMe 2 Si group to 5b in the expectation, based on extensive precedent, that base hydrolysis of the product 8a would afford the β-silyl acid 8b . Several β-silyl acids, made by totally different routes, have been oxidized electrochemically or with Pb­(OAc) 4 to alkenes. However, this plan was thwarted by the fact that ester 5b does not undergo conjugate addition of a PhMe 2 Si group from a cuprate , or an organocopper reagent under conditions that are successful with unsaturated esters that are not also enol ethers. ,, …”

“…15 min), were combined and evaporated. Flash chromatography of the residue over silica gel (1.5 × 10 cm), using 100:1 hexane/EtOAc, afforded 4ee (0.013 g, 79%) as a colorless oil which was a mixture of isomers: FTIR (film) 2959, 2927, 2855, 1723, 1463, 1265, 1126, 805, 742 cm −1 ; 1 H NMR (700 MHz, CDCl 3 ): δ 2.29 (q, J = 7.4 Hz, 2H, minor isomer), 2.41 (q, J = 7.5 Hz, 2H, major isomer), 2.64 (t, J = 7.9 Hz, 2H, minor isomer), 2.67 (t, J = 7.9 Hz, 2H, major isomer), 4.15 (d, J = 5.4 Hz, 2H, minor isomer), 4.25 (d, J = 5.3 Hz, 2H, major isomer), 4.40 (q, J = 6.8 Hz, 1H, major isomer), 4.83 (dt, J = 12.5, 7.4 Hz, 1H, minor isomer), 5.17−5.21 (m, 2H, minor isomer), 5.25−5.30 (m, 2H, major isomer), 5.85−5.90 (m, 1H, both isomers), 5.93 (d, J = 6.2 Hz, 1H, major isomer), 6.22 (d, J = 12.5 Hz, 1H, minor isomer), 7.15−7.20 (m, 3H, both isomers), 7.25− 7.28 (m, 2H, both isomers); 13 C{ 1 H} NMR (100 MHz, CDCl 3 ): δ 25.7 (t), 29.8 (t), 35.9 (t), 37 rac-(2R,3S)-2-[(tert-Butyldiphenylsilyl)oxy]-5-phenyl-3-(phenylsulfanyl)pentanoic Acid (4f). Acid 3i (0.309 g, 1.02 mmol) was dissolved in THF (25 mL), and the solution was cooled to 0 °C.…”

“…6b Because of the difficulty in hydrolyzing phenylthio ester 6g, we considered a related process that would more easily accommodate ester hydrolysis. The plan (Scheme 8) was to effect conjugate addition of a PhMe 2 Si group 34 to 5b in the expectation, based on extensive precedent, 35 37 to alkenes. However, this plan was thwarted by the fact that ester 5b does not undergo conjugate addition of a PhMe 2 Si group from a cuprate 34,38 or an organocopper reagent under conditions that are successful with unsaturated esters that are not also enol ethers.…”

Magnesium-induced regiospecific C-silylation of suitably substituted enoates and dienoates

“…These stabilizing effects play important roles in directing the regioselectivity in various organic reactions, especially in b-silyl carbonyl compounds. Some recent examples include BaeyereVilliger oxidation, 9 BamfordeStevens reaction, 10 Beckmann fragmentation, 11 Curtius reaction, 12 Norrish type I and II cleavages, 13 palladium-catalyzed nucleophilic substitution, 14 Nazarov cyclizations, 15 decarboxylation reactions, 16 stereospecific 1,2-silyl shifts, 17 and cyclobutane 18 formation.…”

Silicon assisted diversified reaction of a β-silylmethylene malonate with dimethylsulfoxonium methylide

“…This stabilizing effect also plays an important role in directing the regioselectivity in various organic reactions. Some recent examples include Baeyer-Villiger oxidation [16], Bamford-Stevens reaction [17], Beckmann fragmentation [18,19], Curtius reaction [20], Norrish types I and II cleavages [21,22], palladium-catalyzed nucleophilic substitution [23], Nazarov cyclizations [24,25], decarboxylation reactions [26] and stereospecific 1,2-silyl shifts [27,28]. The propensity of b-elimination of organosilicon compounds was first demonstrated by Peterson [29,30] for olefin synthesis.…”