The preferred steric course of quaternisation of 1-alkylpiperidines

Abstract

Previous methods of assignment of configuration to pairs of diastereoisomeric quaternary salts of type ⁺NR¹R²X^–, ⁺NR²R¹X^– derived from N-alkylpiperidines are re-examined and their general utility confirmed. Our previous conclusion, that axial attack is preferred in most reactions of marked stereoselectivity, is extended to cover a preference of boat-axial (formally, equatorial) attack in certain 3-azabicyclo[3,3,1]nonanes. The ambiguous position regarding quaternisations of N-alkylnor-tropanes, -tropines, and -pseudotropines is discussed. Other workers' results, arguments, and conclusions are examined