New and Efficient Route to Pipecolic Acid Derivatives by Means of Rh-Catalyzed Intramolecular Cyclohydrocarbonylation

摘要

Recently, the syntheses of biologically active 2,6-disubstituted piperidine alkaloids have attracted significant interest. For the syntheses of these piperidine alkaloids, 6-alkoxypipecolates and 5,6-dehydropipecolates serve as versatile key intermediates and find a variety of applications in the syntheses of izidine alkaloids. 6-Alkoxypipecolates can be synthesized through anodic oxidation and 5,6-dehydropipecolates can be obtained from 2-alkoxypipecolates via dealkoxylation under acidic conditions. We report here the new and convenient syntheses of 6-alkoxypipecolates, 5,6-didehydropipeco-lates, and their derivatives from allylglycinates through extremely regioselective intramolecular cyclohydrocar-bonylation.