Asymmetric synthesis of α-sulfinylphosphonates in the thiolane series

Michael addition to a chiral non-racemic 2-phosphono-2,3-didehydrothiolane S-oxide

“…The X-ray analysis of an isolated single crystal of 1 showed that it was a single enantiomer whose absolute configuration at sulfur atom was assigned as (S). 2 This was in agreement with other results already obtained in the enantioselective sulfoxidation with the same oxaziridine. 1c,5…”

“…When an attempt was made to measure the enantiomeric excess of product 1 using (R)-(+)-tert-butyl(phenyl)-phosphinothioic acid [(+)-TBPPTA] as a chiral solvating agent, 4 only one signal was detected in 31 P NMR, which led us to the conclusion that its ee was at least 98%. 2 Control of the enantiomeric excess by chiral HPLC was impossible since no conditions to separate enantiomers could be found. The X-ray analysis of an isolated single crystal of 1 showed that it was a single enantiomer whose absolute configuration at sulfur atom was assigned as (S).…”

“…2 Nevertheless, the originally reported stereochemistry at the sulfur atom determined by X-ray analysis of an isolated single crystal of (+)-1 was correct.…”

“…2 The separation of the product from the imine resulting from the oxaziridine was improved by first using pure CH 3 CN as the eluent to remove the less polar imine, then a mixture of CH 3 CN/DMSO 10/1.…”

Michael Additions to Activated Vinylphosphonates

“…Krawczyk et al 25 have shown that dicyclohexyloammonium 2-(diethoxyphosphoryl)acrylate (86), obtained by condensation of paraformaldehyde with dicyclohexylam-monium diethoxyphosphorylacetate (85), is also an effective Michael acceptor. Additions performed with this acceptor did not require a basic catalyst and were therefore termed self-catalytic Michael reactions.…”