ChemInform Abstract: Synthesis and X‐Ray Crystal Structures of Chiral, Nonracemic 5,6‐Dihydro‐4H‐1,3,4‐oxadiazines.

Abstract

Synthesis and X-Ray Crystal Structures of Chiral, Nonracemic 5,6-Dihydro--4H-1,3,4-oxadiazines. -The Ephedra-based oxadiazines (IV), (VII) and (VIII) are synthesized as potential tools for conducting asymmetric syntheses via intramolecular chiral relay. Their syntheses are achieved by N-acylation, followed by acid-catalyzed cyclization. Treating the hydrazides (III) and (VI) with either sulfuric acid or hydrobromic acid affords the trans-oxadiazines (IV) and (VII), or cis-oxadiazine (VIII), resp. The preparation of oxadiazines (XII) from hydrazide (IX) is accomplished using a hydrazide pathway with formation of a labile mesylate intermediate. The yields for oxadiazines (XII) are significantly better than those obtained by using the acid-catalyzed pathway, possibly due to the circumvention of hydrazide hydrolysis. -(HITCHCOCK*, S. R.; DEAN, M. A.; KELLEY, C. J.; EDLER, K. L.; FERRENCE, G. M.; J. Heterocycl. Chem. 47 (2010) 4, 982-989, http://dx.