Fused Silacarbacycles Containing a Silole Unit: 1,2‐Hydroboration and 1,1‐Organoboration of Alkynyl(vinyl)silanes

Abstract

The reaction of various alkynyl(vinyl)silanes containing two alkynyl groups with 9‐borabicyclo[3.3.1]nonane (9‐BBN) proceeds by regioselective 1,2‐hydroboration of the vinyl group in the first step, followed by two intramolecular 1,1‐organoboration reactions to afford 1,6‐disilapentalene derivatives, fused silacarbacycles with a silole unit. Similarly, the analogous reaction of an alkynyl(allyl)silane gives a 1,7‐disilaindene derivative. The products were characterized by multinuclear magnetic resonance (1H, 11B, 13C and 29Si NMR) in solution and in two cases by X‐ray structural analysis in the solid state.

Activation of Silicon- and Tin-Carbon Bonds. 1,1-Carboboration of Alkynylsilanes and -stannanes

“…Moreover, the hydrogen atom of the ethynyl group can be replaced by many other substituents, including silyl groups. If an alkynylsilyl group is used, further intra-molecular 1,1-carboboration affords a silole derivative (Scheme 10) (Wrackmeyer et al, 2010, Wrackmeyer et al, 2014b. The 13 C NMR spectrum of such a silole is shown ( Figure 5).…”

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

“…Moreover, the hydrogen atom of the ethynyl group can be replaced by many other substituents, including silyl groups. If an alkynylsilyl group is used, further intramolecular 1,1‐carboboration affords a silole derivative (Scheme ) 80,82. The 13 C NMR spectrum of such a silole is shown in Figure 7.…”

“… 13 C{ 1 H} NMR spectrum (125.8 MHz, C 6 D 6 , 296 K) of a bicyclic silole derivative. Coupling constants n J ( 29 Si, 13 C) in Hz are given in brackets 82…”

“…If the number of C≡C bonds, separated by SiMe 2 units, is increased, the way is opened to condensed siloles (Scheme , Scheme ) 80,82,83…”

“… Cascade‐type sequence of 1,2‐hydroboration and three 1,1‐carboborations of Me 2 Si(CH=CH 2 )–C≡C–SiMe 2 –C≡C–SiMe 2 –C≡C–R 1 leads to condensed siloles 80,82…”