TY - JOUR
T1 - Stereospecific and regioselective reactions of silacyclopropanes with carbonyl compounds catalyzed by copper salts
T2 - Evidence for a transmetalation mechanism
AU - Franz, Annaliese K.
AU - Woerpel, K. A.
PY - 1999/2/10
Y1 - 1999/2/10
N2 - Silacyclopropanes reacted with carbonyl compounds under mild conditions (10 mol % metal salt, ≤22°C) in a stereospecific and highly stereo-, regio- , and chemoselective fashion. In most cases, CuI or CuBr2 were the optimal catalysts although ZnBr2 worked comparably well in a few examples. Insertion occurred with retention of configuration and, in the case of enals and formamides, with high diastereoselectiyity at the newly formed stereogenic centers. For unsymmetrical substrates, insertion occurred at the more substituted carbon-silicon bond with complete regioselectivity. Competition experiments demonstrated that formamides reacted faster than enals, which reacted faster than enoates; saturated aldehydes did not undergo insertion. With a cis-disubstituted silacyclopropane, products of silylene transfer were observed. The stereochemistry, regiochemistry, and chemoselectivity of carbonyl insertion as well as the silylene transfer processes can be explained by a mechanism involving transmetalation of silicon to copper.
AB - Silacyclopropanes reacted with carbonyl compounds under mild conditions (10 mol % metal salt, ≤22°C) in a stereospecific and highly stereo-, regio- , and chemoselective fashion. In most cases, CuI or CuBr2 were the optimal catalysts although ZnBr2 worked comparably well in a few examples. Insertion occurred with retention of configuration and, in the case of enals and formamides, with high diastereoselectiyity at the newly formed stereogenic centers. For unsymmetrical substrates, insertion occurred at the more substituted carbon-silicon bond with complete regioselectivity. Competition experiments demonstrated that formamides reacted faster than enals, which reacted faster than enoates; saturated aldehydes did not undergo insertion. With a cis-disubstituted silacyclopropane, products of silylene transfer were observed. The stereochemistry, regiochemistry, and chemoselectivity of carbonyl insertion as well as the silylene transfer processes can be explained by a mechanism involving transmetalation of silicon to copper.
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U2 - 10.1021/ja982897u
DO - 10.1021/ja982897u
M3 - Article
AN - SCOPUS:0033540626
SN - 0002-7863
VL - 121
SP - 949
EP - 957
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 5
ER -