Abstract

Stilbene type olefins can be prepd. with cis-stereoselectivities approaching 95:5 if tris(2-methoxymethoxyphenyl)phosphine derived ylides are employed and the reaction is carried out at -75 Deg. Thus, treating phosphonium ylide I with p-MeOC6H4CHO in THF contg. LiBr 2.5 h at -75 Deg gave 99% stilbenes II with a Z/E ratio of 96:4. [on SciFinder (R)]

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