Preparation and Reactions of 2-Aryl-3-silyl-1,3-butadienes

Significance

The authors present a novel route for the preparation of silyl-aryl and unsymmetrical 2,3-biarylbutadienes that possesses a number of advantages compared to the known ones. The synthesis of the diene system is based on an interesting carbometallation reaction of alkynes. In the presence of a nickel catalyst, alkynes react with bis(iodozincio)methane. The product eliminates zinc alkoxide, giving a dienyl zinc species, which is coupled in situ with the aryl iodides in the presence of the same Ni catalyst. Interestingly, palladium catalysts are not effective in this reaction. The dienylzinc species thus formed can possibly be trapped by other electrophiles. The silyl moiety on the diene system serves for the second cross-coupling reaction (Hiyama coupling), provided that the silicon atom bears a proper substituent, which allows the formation of a hypercoordinated silicon species, capable for the coupling process.