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DOI: 10.1055/sos-SD-104-00395

Delvos, L. B.; Oestreich, M.Science of Synthesis Knowledge Updates, (20171135.

Metal-free Si—B bond activation (see General Introduction) of silylboronic ester 19 with an in situ generated N-heterocyclic carbene as Lewis base allows the 1,4-silylation of α,β-unsaturated acceptors 193.[‌110‌] The active catalyst is formed by deprotonation of the imidazolinium salt 192 with 1,8-diazabicyclo[5.4.0]undec-7-ene (Scheme 79). A biphasic medium (H2O/THF) is ideal for this transformation, and a range of representative cyclic β-silylated ketones 194 are obtained with good enantioselectivity; the enantiomeric excess for the unsaturated lactone 195 is, however, low (Scheme 79).

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Meeeeeeeeee 88

e M8 ee (%) Meeee (%) Mee
8 M 88 >88 [‌888‌]
8 M 88 88 [‌888‌]
8 M 88 88 [‌888‌]
8 M >88 88 [‌888‌]
8 Me 88 88 [‌888‌]

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Meeeeeeeeee 88

M8 M8 ee (%) Meeee (%) Mee
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Me eMe 88 88 [‌888‌]
Me (MM8)8Me 88 88 [‌888‌]
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