A concise and stereospecific one-shot synthesis of bicyclo[3.3.1]nonenols from dimethyl 1,3-acetonedicarboxylate and enals via the sequential Michael addition - Intramolecular aldolization

The reactions of dimethyl 1,3-acetonedicarboxylate 1 with enals 2 proceeded very smoothly in the presence of a catalytic amount of tetrabutylammonium fluoride or piperidine in THF at room temperature, giving the corresponding bicyclo[3.3.1]nonane derivatives 3 in high yields. Both of the two fused rings of 3 are newly constructed from the starting two acyclic substrates via the sequential Michael addition-intramolecular aldolization in one shot.