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1,1‐allylboration of bis(silyl)ethynes: electron‐deficient SiHB bridges and novel heterocycles via intramolecular hydrosilylation
Author(s) -
Wrackmeyer Bernd,
Tok Oleg L.,
Bubnov Yuri N.
Publication year - 2004
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.555
Subject(s) - chemistry , hydrosilylation , silylation , intramolecular force , ring (chemistry) , medicinal chemistry , stereochemistry , silicon , organic chemistry , catalysis
The reaction of bis(silyl)ethynes 2 – 4 , bearing one, two and three hydrides at one of the silicon atoms, with triallylborane 1 leads primarily to alkenes 5 , 8 and 11 respectively by 1,1‐allylboration. In these alkenes, the diallylboryl and the silyl group bearing one or more SiH functions are in cis‐positions at the CC bond, giving rise to the formation of an electron‐deficient SiHB bridge. This follows unambiguously from the consistent set of NMR data, in particular from the observation of isotope‐induced chemical shifts 2 Δ 10/11 B( 29 Si). The activation of the SiH bond in 5 , 8 and 11 induces intramolecular hydrosilylation under very mild reaction conditions to give 1,4‐silabora‐cyclo‐2‐heptenes 7 , 10 and 13 respectively. Upon heating, these seven‐membered heterocycles undergo ring contraction by 1,1‐deallylboration to give the 1‐sila‐cyclo‐2‐hexenes 14 – 16 , and bear an exocyclic diallylboryl group in 3‐position. All proposed structures are based on consistent 1 H, 11 B, 13 C and 29 SiNMR data. Copyright © 2004 John Wiley & Sons, Ltd.