Nucleophilic additions to alkylidene bis(sulfoxides): stereoelectronic effects in vinyl sulfoxides.

Conjugate additions of nucleophiles (e.g. enolates, amines and malonate anions) to bis(p-tolylsulfinyl)alkenes, alkylidene-1,3-dithiane-1,3-dioxides and alkylidene-1,3-dithiolane-1,3-dioxides have recently been published.

Stereoelectronic effects in cyclic sulfoxides, sulfones, and sulfilimines: application of the Perlin effect to conformational analysis.

The 1JC--H coupling constants in conformationally constrained sulfoxides, bissulfoxides, sulfoxide-sulfones, and sulfilimines derived from 2-benzylidene-1,3-dithiane and 2-(2,2-dimethylpropylidene)-1,3-dithiolane were measured by means of HMQC and HSQC NMR experiments and the Perlin effects were calculated. The type and the relative configuration of S==X groups (X= O, NTos) in these compounds have a strong influence on the magnitude of coupling constants for axial and equatorial C--H bonds, respectively. Axial S==O bonds give rise to a stereoelectronic effect on antiperiplanar axial C--H bonds.

Enolate addition to a 2-alkylidene[1,3]dithiane-derived bissulfoxide. A new a(2)-acceptor.

Reaction of enolates derived from esters and ketones to an easily prepared alkylidene[1,3]dithiane-1,3-dioxide afforded the respective adducts with good yields and selectivities generally exceeding 85:15. The base used for enolate addition played no significant role for the reaction outcome, and addition of a silyl enole ether gave similar results. The thus formed oxygenated S,S-acetals were transformed into the corresponding 1,4-dicarbonyls by a reduction/oxidation sequence with 84% yield.