Chem Asian J. 2017 Jun 01;12(11):1224-1233. doi: 10.1002/asia.201700125. Epub 2017 Mar 30.

Stereoisomerization of Cyclic Silanols.

Chemistry, an Asian journal

Hisayuki Endo, Nobuhiro Takeda, Masafumi Unno

PMID: 28224762 DOI: 10.1002/asia.201700125

Abstract

Stereoisomerization of readily available all-cis-1,3,5,7-tetrahydroxy-1,3,5,7-tetraisobutylcyclotetrasiloxane (1 a) was carried out under acidic conditions to afford cis-trans-cis (1 b), all-trans (1 c), and cis-cis-trans (1 d) isomers. The compounds in the reaction mixture could be easily separated into 1 a and a mixture of 1 b, 1 c, and 1 d by the treatment with chloroform. Compounds 1 b, 1 c, and 1 d were further separated and isolated, and each structure was identified. The experimental results indicated that the most plausible mechanism is a substitution reaction at the silicon center via a pentacoordinate intermediate without a cyclic siloxane bond cleavage reaction. The obtained isomer 1 a or 1 b further reacted with dichlorodiphenylsilane in the presence of triethylamine to give syn-type laddersiloxane (2 a) or anti-type laddersiloxane (2 b), respectively.

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Keywords: isomerization; materials science; reaction mechanisms; silicon; structure elucidation

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• Journal Article