Stereoselective synthesis of olefins by a reductive coupling reaction.

Ketones and aldehydes are converted to symmetrical and (E)-olefins (1-15) by reaction with 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide (PhPSe(2))(2), Woollins' reagent, in refluxing toluene; use of diketones was demonstrated by the reaction of PhC(O)CH(2)C(O)Ph which gives 1,2,4,5-tetraphenylbenzene (16) in 83% yield.