Abstract
A silicon-tether ring-closing metathesis strategy is reported for the synthesis of trisubstituted olefins flanked by allylic or homoallylic alcohols, which are difficult to obtain by classical ring-closing or cross-metathesis reactions. In addition, a novel Peterson olefination reaction has been developed for the preparation of the allyldimethylsilane precursors, which are versatile synthetic intermediates. This method was then applied to the synthesis of the C16-C30 fragment of dolabelide C.
Highlights
N umerous natural products of the polyketide family encompass an E trisubstituted olefin with a methyl substituent
Hoye and co-workers attempted to close the macrocycle in callipeltoside by ring-closing metathesis (RCM) reaction to form the C10−C11 trisubstituted alkene.1h only starting materials were recovered, or truncated products were obtained when using relay ring-closing metathesis strategies,[3] highlighting the lack of efficiency of metathesis reactions for hindered substrates
Trisubstituted enone 3 was only 47%, because Z enone 1 isomerized into the unreactive E isomer in the presence of metathesis catalysts, showing the limitations of cross metathesis (CM) for the synthesis of highly hindered trisubstituted olefins.[6]
Summary
N umerous natural products of the polyketide family encompass an E trisubstituted olefin with a methyl substituent. Synthesis of Trisubstituted Olefins by Metathesis Reactions During our previous studies toward the synthesis of dolabelide C,4 we constructed the C16−C30 fragment[5] using a cross metathesis (CM) reaction between Z disubstituted enone 1 and gem-disubstituted olefin 2 to form trisubstituted olefin 3 (Scheme 1).
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