1,1‐Organoboration of bis(trimethylstannyl)ethyne with trimethylsilyl‐ and dimethylsilyl‐dialkylboryl‐substituted alkenes: organometallic‐substituted allenes

Abstract

The reactions of bis(trimethylstannyl)ethyne, Me 3 Sn-C C-SnMe 3 (4), with trimethylsilyl-or dimethylsilyl-dialkylboryl-substituted alkenes 1-3 afford organometallic-substituted allenes 5, 6 and 8, 9 in high yield. In the case of (E)-2-trimethylsilyl-3-diethylboryl-2-pentene (1), a butadiene derivative 7 could be detected as an intermediate prior to rearrangement into the allene. All reactions were monitored by 29 Si and 119 Sn NMR, and the products were characterized by an extensive NMR data set ( 1 H, 11 B, 13 C, 29 Si, 119 Sn NMR).

Synthesis and molecular structures of 1‐boracyclopent‐2‐enes

“…Two of these heterocycles were crystallized to study their molecular structure by X-ray diffraction, and all could be analyzed in solution by NMR spectroscopy of all NMR-suitable nuclei ( 1 H, 11 B, 13 C, 29 Si and 119 Sn). Most of the data are collected in Table 1.…”

“…An alternative is the activation of one of the B-C(9-BBN) bonds leading to expansion of the bicyclic system in the intermediate III, which is a dialkenylborane. In the next step, both intermediates II and III Table 1. 11 B, 13 C, 29 Si and 119 Sn NMR data a of 1-boracyclopent-2-enes 8-14 [11] for comparison.…”

“…[11,13,20] The low frequency shift by about 15 ppm relative to the starting materials is typical for the borol-2-enes and by about 7-10 ppm for the allenes containing the boryl group in an allylic position. [11] X-ray Structure Analyses of 8b and 10b…”

“…[11] In the course of a systematic study, we became interested in the influence of Si-Cl functions and other substituents on the product distribution arising from such reactions.…”

“…The reactions were monitored by multinuclear magnetic resonance spectroscopy ( 1 H, 11 B, 13 C, 29 Si, 119 Sn NMR), and the molecular structures of two new heterocycles were determined by X-ray crystallography.…”