A versatile stereoselective diversity oriented synthetic pathway to the possible spiro and fused diverse heterocyclic small molecules is described. The strategy involved the "build–couple–pair" approach involving an S N Ar, Michael addition and Mannich reaction on chiral acyl bicyclic lactams 2a/b, followed by a cyclization onto the inbuilt scaffold electrophile, thereby leading to asymmetric fused and spirocyclic nitrogen heterocycles. A "post-pair" phase has been incorporated to generate more polar compounds.
Piperidine is used as a solvent and as a base. The same is true for certain derivatives: N-formylpiperidine is a polar aprotic solvent with better hydrocarbon solubility than other amide solvents, and 2,2,6,6-tetramethylpiperidine is a highly sterically hindered base, useful because of its low nucleophilicity and high solubility in organic solvents.
