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Alkynenitriles: stereoselective chelation controlled conjugate addition–alkylations

✍ Scribed by Fraser F. Fleming; Venugopal Gudipati; Omar W. Steward

Book ID
104205429
Publisher
Elsevier Science
Year
2003
Tongue
French
Weight
221 KB
Volume
59
Category
Article
ISSN
0040-4020

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✦ Synopsis

Chelation-controlled conjugate addition of Grignard reagents to g-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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