Sequential cross-coupling of 1,4-bissilylbutadienes: synthesis of unsymmetrical 1,4-disubstituted 1,3-butadienes.

A mild and general and stereospecific cross-coupling reaction of unsymmetrical 1,4-bissilyl-1,3-butadienes has been accomplished. By the use of either a benzyldimethylsilyl or 2-thienyldimethylsilyl unit at one end of the dienylsilanol, a selective cross-coupling could be effected under mildly basic conditions (KOTMS) to afford 4-aryl-1,3-dienylsilanes in excellent yield for a wide range of aryl and alkenyl coupling partners. The second cross-coupling could be effected cleanly by the action of TBAF with electron-rich or electron-poor halides. The sequential process could be telescoped into a "one pot" procedure with overall excellent yields of the unsymmetrical 1,4-diaryl-1,3-butadienes.