Reduction of 6-hydroxyimino-1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane and nitrosation of the resulting amines. New rearrangement products of the monoterpenoid 1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane

Abstract

Reduction of 6-hydroxyimino-1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane (1) with lithium aluminium hydride in diethyl (or better di-isopropyl) ether and nitrosation of the reaction mixture gave in fair yield N-nitroso-5,7,7-trimethyl-6-oxa-3-azabicyclo[3.2.2]nonane (5), which in turn afforded in good yield 5,7,7-trimethyl-6-oxa-3-azabicyclo[3.2.2]nonane (4) by treatment with copper(I) chloride in conc. hydrochloric acid. Reduction of (1) with lithium aluminium hydride in tetrahydrofuran, or better with sodium bis-(2-methoxyethoxy)aluminium hydride in benzene, gave 5,7,7-trimethyl-6-oxa-3-azatricyclo[3.2.2.0^2,4]nonane (6), which afforded, via nitrosation, 1,3,3-trimethyl-2-oxabicyclo[2.2.2]oct-5-ene (7) in excellent yield. Catalytic reduction of (1) gave in high yield an 80 : 20 mixture of cis- and trans-6-amino-1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane (2) and (3), respectively. Nitrosation of (2) gave a near quantitative yield of 1-[3-(1-hydroxy-1-methylethyl)cyclopentyl]ethanone (9), whereas (3) afforded the known cis-4-hydroxy-4,7,7-trimethyl-6-oxabicyclo[3.2.1]octane (11). The structures of the new compounds reported were determined from i.r., n.m.r., and mass spectral data.