Asymmetric conjugate additions to chiral bicyclic lactams. Synthesis of aracemic trans-2,3-disubstituted pyrrolidines
摘要:
The trans-2,3-disubstituted pyrrolidine moiety, found in the pyrrolizidine alkaloids as well as other natural products, has been accessed from the alpha,beta-unsaturated bicyclic lactams 1d and 10. Conjugate addition of lower order cyanocuprates to lactams 1d and 10 resulted in endo entry of the cuprate with high diastereoselectivity. Other cuprates were investigated and resulted in diminished or opposite stereoselectivities. Further transformation of the beta-substituted lactams provided the title compounds in good overall yield and high enantiomeric excess.
Asymmetric conjugate additions to chiral bicyclic lactams. Synthesis of aracemic trans-2,3-disubstituted pyrrolidines
摘要:
The trans-2,3-disubstituted pyrrolidine moiety, found in the pyrrolizidine alkaloids as well as other natural products, has been accessed from the alpha,beta-unsaturated bicyclic lactams 1d and 10. Conjugate addition of lower order cyanocuprates to lactams 1d and 10 resulted in endo entry of the cuprate with high diastereoselectivity. Other cuprates were investigated and resulted in diminished or opposite stereoselectivities. Further transformation of the beta-substituted lactams provided the title compounds in good overall yield and high enantiomeric excess.
Tertiaryamine N-oxides were used to stereospecifically epoxidize chiral unsaturated bicyclic lactams in high yields (90–99%) at room temperature. This appears to be the first reported example of tertiaryamine N-oxides acting as epoxidizing agents in the absence of a metal catalyst.
[2 + 2] and [3 + 2] Cycloadditions of Triisopropylallylsilane to .alpha.,.beta.-Unsaturated Bicyclic Lactams
作者:Gregory P. Brengel、C. Rithner、A. I. Meyers
DOI:10.1021/jo00097a013
日期:1994.9
Addition of allylsilane gave cyclobutanes at low temperature and cyclopentanes at higher temperature.
Allyldimethyltritylsilane: construction of enantiomerically pure cyclobutano[c]fused pyrrolidines
作者:Michael D Groaning、Gregory P Brengel、A.I Meyers
DOI:10.1016/s0040-4020(01)00083-7
日期:2001.3
Cyclobutannulation of the bicyclic lactam with allyldimethyltritylsilane is accomplished in high yield with good diastereoselectivity. The resulting tricyclic system is converted to a enantiomerically pure cyclobutane-fused pyrrolidine. (C) 2001 Elsevier Science Ltd. All rights reserved.
Brengel Gregory P., Rithner C., Meyers A. I., J. Org. Chem, 59 (1994) N 18, S 5144-5146