1,1‐Carboboration through Activation of Silicon–Carbon and Tin–Carbon Bonds

摘要: In the course of 1,1-carboborations, activation polar Si–C and Sn–C bonds by electrophilic triorganoboranes (BR3, R = alkyl, aryl, C6F5) is used to build new C–C bonds. As would be expected, organotin compounds were found much more reactive than corresponding silanes, Sn–C(sp) other tin–carbon Monoalkynyl derivatives lead organometallic-substituted alkenes, quantitatively stereoselectively in most cases. Dialkynylsilanes R22Si(C≡C–R1)2 (R1 silyl; R2 H, allyl, vinyl, Cl) react with BR3 twofold 1,1-carboboration through selective formation siloles. case dialkynylstannanes R22Sn(C≡C–R1)2, benzyl, amino) analogous reactions mainly stannoles or alternatively 1-stanna-4-bora-cyclohexa-2,5-diene derivatives, a way that depends complex manner on substituents at boron R1 C≡C bond. Vinyltin also 1,1-carboboration. The high reactivity allows conducted under mild conditions, enabling isolation structural characterisation intermediates. These are zwitterionic structure, which typically an almost trigonal-planar surrounded tin atom coordinated "side-on" bond alknylborate unit. On extending these reaction principles tetraalkynylsilanes Si(C≡C–R1)4, one obtains 1,1′-spirobisiloles fourfold Similarly, 1,1′-spirobistannoles can prepared starting from tetraalkynylstannanes Sn(C≡C–R1)4 iPr, tBu, SiMe3). Combination 1,2-hydroboration opens numerous silicon heterocycles, not readily available any method.