Gold-Catalyzed Dehydrogenative Cycloaddition of Tethered 1,n-Dihydrodisilanes to Alkynes

Gold nanoparticles supported on TiO2 (0.1-2% mol) catalyze at mild conditions the dehydrogenative addition of tethered 1,n-dihydrodisilanes, such as 1,1,3,3-tetramethyldisiloxane (1), 1,1,3,3-tetraphenyldisiloxane (2), 1,1,1,3,5,7,7,7-octamethyltetrasiloxane (3), 1,1,3,3,5,5-hexamethyltrisiloxane (4), and 1,2-bis(dimethylsilyl)benzene (5), to alkynes, forming cycloadducts and releasing H-2. Under the same conditions, polymeric methylhydrosiloxane is completely unreactive. For the majority of terminal alkynes and 1,n-dihydrodisilanes the yields are excellent (up to 99%). In general, terminal alkynes are more reactive as compared to internal. The reaction tolerates several functional groups and can be performed in a variety of solvents. In the case of 1,1,3,3-tetramethyldisiloxane, it is proposed that gold nanoparticles form intermediate cyclo-gold-tetramethyldisiloxane via a dehydrogenative pathway, which undergoes a formal [3+2] cycloaddition to alkynes.