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

Abstract

Abstract:In the course of 1,1-carboborations, the activation of polar Si-C and Sn-C bonds by electrophilic triorganoboranes (BR 3 , R = alkyl, aryl, C 6 F 5 ) is used to build new C-C bonds. As would be expected, organotin compounds were found to be much more reactive than the corresponding silanes, and Sn-C(sp) bonds were more reactive than other tin-carbon bonds. Monoalkynyl derivatives lead to organometallic-substituted alkenes, quantitatively and stereoselectively in most cases. Dialkynylsilanes R 2 2 Si(C≡C-R 1 ) 2 (R 1 = alkyl, aryl, silyl; R 2 = H, alkyl, allyl, vinyl, aryl, Cl) react with BR 3 by twofold 1,1-carboboration through selective formation of siloles. In the case of dialkynylstannanes R 2 2 Sn(C≡C-R 1 ) 2 , (R 1 = alkyl, aryl, silyl; R 2 = alkyl, benzyl, aryl, amino) the analogous reactions lead mainly to stannoles or alternatively to 1-stanna-4-bora-cyclohexa-2,5-diene derivatives, in a way that depends in a complex manner on the sub-

Boron and Silicon-Substituted 1,3-Dienes and Dienophiles and Their Use in Diels-Alder Reactions

“…Wrackmeyer and Khan have worked in this area for a number of years and authored a microreview that appeared in 2016 ( Scheme 9 ) [ 13 ]. The synthetic chemistry covered involves 1,1-carboboration of diynes ( 30 ) to yield boroles ( 31 ), siloles, and stannoles.…”

Experimental and Theoretical Studies of a Spirostannole and Formation of a Pentaorganostannate

“…Stannoles, on the other hand, have been investigated less often. However, as different high-yielding synthetic methods have emerged, their optical, electronic, and structural properties and use as building blocks in materials have become a focus of research [ 2 , 3 , 4 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. Aside from their innate properties, their reactivity is also of interest.…”

Syntheses and Properties of Tin‐Containing Conjugated Heterocycles

“…It proceeds through at wo-step pathway (Scheme 14). [51] Initially,a ni ntramolecular activation of one of the SnÀC bonds triggered by the Lewis acidic borane anda 1,1-carboboration occurs.D ue to the favorable stereochemistry in an ext step, the second SnÀC bond is activated intramolecularly.T hen am igration of the alkyne group from the tin atom to boron takes place forming az witterionic intermediate. In a final step, ar earrangementr eaction either leads to the stannole (1,1-vinylboration) or to the stanna-4-bora-cyclohexa-2,5diene (transfero fR ).…”

“…Mechanism of the 1,1-carboboration to obtain stannoles. [51] Scheme15. Synthetic route for stannafluorenes 47, [ Stannoles that are halogenated on the tin atom offer easy access to further substitution and functionalization.T he first halogenation using elemental halogens was reported with 1,1dimethyl-2,3,4,5-tetraphenylstannole (18)w hich led initially to an asymmetric oxidative ring cleavage (Scheme 17).…”

“…Furthermore, the isolation and structural analysis of intermediates was possible and a plausible mechanism could be proposed. It proceeds through a two‐step pathway (Scheme ) . Initially, an intramolecular activation of one of the Sn−C≡ bonds triggered by the Lewis acidic borane and a 1,1‐carboboration occurs.…”