Navigation

0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest.
Please login or sign up for a free trial to access the full content.
20.5.1.7.1.9 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.

Meeeee 88 Meeeeeeee MM Meee Meeeeeeee ee α,β-Meeeeeeeeee Meeeee[‌88‌‌88‌]

Meeeeeeeeeee Meeeeeeee

Meeee 8-Meeeee-8-eeeeeeeeee-8-eeeeee (88, M8=Me; M8=Me; M8=Me); Meeeeee Meeeeeeee:[‌88‌]

M eeeeee 88-eM eeee eeeeeeeeee [MeM8(MMe8)8] (88ee, 8.88eeee), Me8M (88ee, 8.88eeee), eee Me eeeeee (888ee, 8.88eeee) eee eeeeeeeee eee eeeeee eeee M8 ee eeeee eeeeee. Meeeeee eeeeeeeee eeeee MeMM (8.8eM), 8-eeeeeeeeee-8-eee (88, M8=Me; M8=Me; 888ee, 8.88eeee), eeeee eeeeeeee (88, M8=Me; 888ee, 8.88eeee), eee M8M (88.8 µM, 8.88eeee) eeee eeeee ee eee eeeeee eeee ee eeeeeee. Mee eeeeeee eee eeeeeee eee eeeeee ee 88°M eee 88e, eee eee eeee eeeeee, eeeeeee eeee MM8Me8, eee eeeeeee eeeee eee eee 88eee. Mee eeeeeee eee eeeeeeee eeeeeee Meeeee eee e eeeeee eee eee eee eeeeee eeee MM8Me8. Mee eeeeeeee eee eeeeeeeeeeee eee eee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeee/MeMMe); eeeee: 888ee (88%).

References