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Licensed Unlicensed Requires Authentication Published by De Gruyter June 2, 2014

Hydroboration of Bis(Trimethylsilyl)Ethyne. New Aspects of Hydroboration

  • Bernd Wrackmeyer , Oleg. L. Tok , Wolfgang Milius , Moazzam H. Bhatti and Saqib Ali

Abstract

The hydroboration of bis(trimethylsilyl)ethyne, Me3Si-C≡C-SiMe3 1, with 9-borabicyclo [3.3.1] nonane (9-BBN) gives first the expected (Z)-alkene 5 which rearranges, without UV irradiation, after several days quantitatively into the (E)-alkene 6. Heating of 6 in the presence of a further equivalent of 1 leads, again almost quantitatively, to an allene, the 1,1,4,4-tetrakis(trimethylsilyl)-4-[9-(9- borabicyclo[3.3.1]nonyl)]buta-1,2-diene 8. Reactive structures arising from π-σ delocalisation involving the boryl group are proposed to be responsible both for the cis/trans-isomerisation and the allene formation. It is suggested that analogous structures may explain the previously observed formation of allenes 9 and 10, tin-analogues of 8. The structures of 5, 6 and 8 in solution follow from a consistent set of NMR data (1H, 11B, 13C, 29Si NMR), and the solid-state structure of 8 was confirmed by X-ray analysis.

Keywords: Alkynes; Alkenes; Allenes
Published Online: 2014-6-2
Published in Print: 2003-1-1

© 1946 – 2014: Verlag der Zeitschrift für Naturforschung

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