For the first time, easily available N-(alpha-methoxyalkyl)amides were successfully used as synthetic equivalents of N-acylimines in an asymmetric heterocycloaddition process. The facial-controlled formation of 6-alkoxydihydrooxazines was thus achieved by SnCl(4)-promoted heterocycloaddition of (R)-O-vinyl pantolactone. By simple acidic hydrolysis of the crude heteroadducts, new beta-aryl- and beta-alkyl-substituted benzamido aldehydes were thus obtained in good overall yields with high enantioselectivities.
[reaction: see text] The 1,3-oxazine route to enantiopure beta-amido aldehydes was investigated. Heterocycloaddition of the N-acyl imine 1 with (R)-O-vinylpantolactone provided the stable dihydroxazine 4c. High diastereocontrols were observed when using Yb(fod)3-catalyzed or SnCl4-mediated conditions, thus leading after quantitative hydrolysis to (R)-N-benzoyl-3-phenylpropanal with >98% ee.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.