The first example of racemization of the sulfur stereogenic center of α-sulfinyl carbanions at low temperatures

Configurational Stability of Optically Active Dichloromethyl p‐Tolyl Sulfoxide and Its Anionic Species: Experimental and Theoretical Study

“…The choice of countercation is also an important factor for the progress of racemization. As previously reported, when the sulfoxide ( R )‐ 1a was deprotonated with lithium diisopropylamide, the racemization proceeded more slowly than that with KHMDS . Dichloro( p ‐tolylsulfinyl)methylpotassium having an electropositive potassium cation is more likely to undergo the elimination than dichloro( p ‐tolylsulfinyl)methyllithium.…”

“…Therefore, lithium amides are suitable for the generation of anionic species of aryl dichloromethyl sulfoxides in asymmetric synthesis . In the previous study, we proposed a chlorine‐assisted pyramidal inversion mechanism . If the mechanism is operative, chloromethyl p ‐tolyl sulfoxide 2a should also racemize under basic reaction conditions.…”

“…Recently, we established an efficient method for the optical resolution of racemic aryl dichloromethyl sulfoxides 1 utilizing (–)‐menthone as a resolving agent . In the course of our study on the synthetic applications of the sulfoxides 1 , we encountered the facile racemization of the sulfoxides 1 under basic reaction conditions ; however, in general, the S ‐chiral sulfoxides do not readily racemize . Herein, we report an experimental and theoretical study on the configurational stability and racemization mechanism of optically active aryl dichloromethyl sulfoxides.…”

Chiral sulfoxides in the enantioselective allylation of aldehydes with allyltrichlorosilane: a kinetic study

“…14 Moreover the formation of tetracoordinated neutral chlorosulfurane could allow explaining the racemization of the sulfoxide through inversion of configuration at sulfur. 15 Indeed, chlorosulfurane species are reported to hydrolyze and to give back the sulfoxide with partial racemization. 14 In principle a process that involves the reaction and the subsequent deactivation of the sulfoxide through the formation of unstable sulfuranes can start already from the early stages of the allylation reaction as a slow but competing side process.…”

“…In a flame dried two-necked round bottom flask, benzaldehyde 1 (X mmol) was added to a solution of sulfoxide 2 (Y mmol), naphthalene (10.3 mg, 0.0804 mmol), diisopropylethylamine (0.40 mmol) and allyltrichlorosilane (Z mmol), in dry 2 Cl 2 (5.0 mL) at −78 °C under argon. Then aliquots (50 μL) were taken after the time reported in the tables (see experiments [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Each sample was quickly quenched with saturated aqueous NaHCO 3 (0.15 mL) and the resulting mixture was diluted with 1 mL of CHCl 3 .…”