Stereospecific and regioselective reactions of silacyclopropanes with carbonyl compounds catalyzed by copper salts: Evidence for a transmetalation mechanism

Annaliese K. Franz, Keith Woerpel

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish (US)
Pages (from-to)949-957
Number of pages9
JournalJournal of the American Chemical Society
Volume121
Issue number5
DOIs
StatePublished - Feb 10 1999

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Formamides
Carbonyl compounds
Silicon
Copper
Salts
Regioselectivity
Stereochemistry
Aldehydes
Carbon
Metals
Catalysts
Substrates
Experiments

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "Stereospecific and regioselective reactions of silacyclopropanes with carbonyl compounds catalyzed by copper salts: Evidence for a transmetalation mechanism",
abstract = "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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AU - Franz, Annaliese K.

AU - Woerpel, Keith

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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