Nitrosohydrazine Conformations. The Effect of Replacing C(1)-H of 2-Nitroso-2-azabicyclooctane Derivatives by Nitrogen

Article abstract of DOI:10.1021/jo01307a024

Substitution of one and two methyl groups for hydrogens at C(3) of 2-nitroso-2-azabicyclo<2.2.2>octane, 1, which exists entirely in the A conformation (nitroso oxygen syn to C(3)), sterically destabilizes the A conformation.The monomethyl compound (2) exists only 85percent in conformation A, and the B conformation (nitroso oxygen syn to C(1)) predominates for the dimethyl compound, 3 (13percent A, 87percent B).Replacement of C(1)-H by N gives the "homomorphic" nitrosohydrazines 4-6.The monomethyl compound 5 exists 98percent in conformation A and the dimethyl compound 6 60percent in conformation A, so the CH -> N transformation favors conformation A by 1.3 to 1.4 kcal/mol for 2 -> 5 and 3 -> 6.This result is the opposite to that predicted, considering steric, nitroso nitrogen lone pair-?^*, and N(1) lone pair-nitroso nitrogen lone pair interactions.