Addition of Grignard reagents to the unsaturated oxo-nitrile 10 (4-hydroxy-4-methyl-6-oxocyclohex-1-enecarbonitrile) provides conjugate addition products with virtually complete stereocontrol. Mechanistic evidence supports a chelation-controlled conjugate addition via alkylmagnesium alkoxide inter mediates. Diverse Grignard reagents having sp(3)-, sp(2)-, and sp-hybridized carbons react with comparable efficiency, with even sterically demanding nucleophiles adding with complete stereocontrol. Unsaturated oxo-nitriles that are incapable of chelation afford diastereomeric conjugate addition products through an unusual boatlike transition state. Collectively, these reactions illustrate the complementary stereoselectivity of chelation-controlled conjugate additions to hydroxylated, unsaturated oxo-nitriles and stereoelectronically controlled conjugate additions to enones.
Addition of Grignard reagents to the unsaturated oxo-nitrile 10 (4-hydroxy-4-methyl-6-oxocyclohex-1-enecarbonitrile) provides conjugate addition products with virtually complete stereocontrol. Mechanistic evidence supports a chelation-controlled conjugate addition via alkylmagnesium alkoxide inter mediates. Diverse Grignard reagents having sp(3)-, sp(2)-, and sp-hybridized carbons react with comparable efficiency, with even sterically demanding nucleophiles adding with complete stereocontrol. Unsaturated oxo-nitriles that are incapable of chelation afford diastereomeric conjugate addition products through an unusual boatlike transition state. Collectively, these reactions illustrate the complementary stereoselectivity of chelation-controlled conjugate additions to hydroxylated, unsaturated oxo-nitriles and stereoelectronically controlled conjugate additions to enones.
作者:Fraser F. Fleming、Jianping Guo、Qunzhao Wang、Douglas Weaver
DOI:10.1021/jo9909709
日期:1999.11.1
Addition of Grignard reagents to the unsaturated oxo-nitrile 10 (4-hydroxy-4-methyl-6-oxocyclohex-1-enecarbonitrile) provides conjugate addition products with virtually complete stereocontrol. Mechanistic evidence supports a chelation-controlled conjugate addition via alkylmagnesium alkoxide inter mediates. Diverse Grignard reagents having sp(3)-, sp(2)-, and sp-hybridized carbons react with comparable efficiency, with even sterically demanding nucleophiles adding with complete stereocontrol. Unsaturated oxo-nitriles that are incapable of chelation afford diastereomeric conjugate addition products through an unusual boatlike transition state. Collectively, these reactions illustrate the complementary stereoselectivity of chelation-controlled conjugate additions to hydroxylated, unsaturated oxo-nitriles and stereoelectronically controlled conjugate additions to enones.