3α-Acetoxy-6,6-dimethylbicyclo[3.1.1]heptane-2-spiro-1′-cyclopropane from nopylamine deamination

Abstract

Deamination of nopylamine hydrochloride with sodium nitrite in acetic acid yields nopyl chloride 8, nopyl acetate 1 (R = OAc), 2-(1-acetoxyethyl)-6,6-dimethylbicyclo[3.1.1]hept-2-ene 9 and 3α-acetoxy-6,6-dimethylbicyclo[3.1.1]heptane-2-spiro-1′-cyclopropane 12. The products are consistent with initial formation of a diazonium ion which reacts by nucleophilic attack, hydride shift or by shift of electrons of the double bond. The reaction is contrasted with the acetolysis of nopyl toluene-p-sulfonate, which yields 8,8-dimethyltricyclo[4.2.1.0^3,7]nonan-6-ol as the main product. The difference is suggested to result from the transition state being reached early (deamination) or late (toluene-p-sulfonate acetolysis) on the reaction coordinate.