Alkynenitriles: stereoselective chelation controlled conjugate addition-alkylations |
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Authors: | Fraser F Fleming Venugopal GudipatiOmar W Steward |
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Institution: | Department of Chemistry and Biochemistry, Duquesne University, Mellon Hall, Pittsburgh, PA 15282-1530, USA |
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Abstract: | Chelation-controlled conjugate addition of Grignard reagents to γ-hydroxyalkynenitriles stereoselectively generates tri- and tetra-substituted alkenenitriles. t-BuMgCl-initiated deprotonation of hydroxyalkynenitriles followed by addition of a second Grignard reagents triggers a facile conjugate addition leading to a cyclic magnesium chelate. Protonation of the chelate stereoselectively generates trisubstituted nitriles whereas the addition of t-BuLi causes conversion to an ‘ate’ complex that allows alkylation with aldehyde electrophiles. The chelation-controlled conjugate addition-alkylation generates tri- and tetra-substituted alkenenitriles that are otherwise difficult to synthesize. |
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Keywords: | conjugate addition alkynenitriles |
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