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Please login or sign up for a free trial to access the full content. Method 9: Reductive C—C Bond Formation of α,β-Unsaturated Esters

DOI: 10.1055/sos-SD-020-00774

Zhang, M.; Hanson, P. R.Science of Synthesis, (200720873.

The lithium salts of tritylhydrazones 43 of both aldehydes and ketones react with methyl crotonate at low temperature to form C-trapped azo compounds, which decompose homolytically, with loss of nitrogen, below room temperature to afford saturated esters 44 in poor yields (Scheme 12).[‌49‌] The major reaction pathway in these processes appears to be a basic deprotonation of methyl crotonate by azo anions to give recovered tritylhydrazone. In the presence of excess triethylsilane or phenylsilane, α,β-unsaturated esters 45 react with excess alkylmercury(II) chloride in dimethyl sulfoxide to give reductively alkylated products, esters 46, in good to excellent yields in most cases (Scheme 12).[‌50‌,‌51‌] An unusual cobalt(II)-catalyzed intermolecular reductive coupling is that of α,β-unsaturated esters 48 with alkynes 47 to give esters 49 (Scheme 12).[‌52‌] This reaction is highly chemo-, regio-, and stereoselective, providing an effective route for CC bond formation under mild conditions.

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