Chemoselective Multicomponent Condensation of 1,3-Cyclohexanedione, Urea or Thiourea with Aldehydes: One-Pot Synthesis of Two Families of Fused Heterobicyclic and Spiro-fused Heterobicyclic Aliphatic Rings

One-pot chemoselective condensation of 1,3-cyclohexanedione, urea or thiourea with aldehydes has been performed by using TMSCl as a Lewis acid in DMF/MeCN.This extended Biginelli-type reaction afforded two families of fused heterobicyclic and spiro-fused heterobicyclic compounds in excellent yields. para-Substituted benzaldehydes exhibited different chemical behaviors to ortho-or meta-substituted benzaldehydes and aliphatic aldehydes.The possible mechanism was discussed to account for experimental results.