The proton magnetic resonance spectra of hexahydropyrrolizine, its salts, its 3-methyl derivatives, and its methiodide

Abstract

The spectra are discussed and many assignments made from considerations of the bond anisotropies. Double resonance provided some checks and gave |J_gem| for the α-methylene protons of hexahydropyrrolizine.

Over the range –70 to +190° hexahydropyrrolizine exists mainly, if not entirely, in the cis-fused form. The 3-endo-methyl derivative, however, shows rapid nitrogen inversion at room temperature, and only below –60° does it exist predominantly in the cis-fused form. Incidentally, the configurations of the two stereoisomers of 3-methylhexahydropyrrolizine were confirmed.

The shielding of the methyl group in hexahydropyrrolizine methiodide is compared with that in the methiodides of cis-and trans-octahydroindolizine and of trans-octahydroquinolizine.