We report herein a novel diastereo- and enantiocontrolled preparation of polysubstituted cyclopentanes by the formal [3+2] cycloadditions of vinyl cyclopropanes with enals. In constrast with previously developed strategies, our original approach is based on the synergistic merger of iminium/enamine organocatalysis with palladium(0) catalysis.

Various heterocyclic systems based on natural and unnatural biologically active products were synthesized by Brønsted acid-promoted cyclization. We have made an attempt to summarize the progress made in this area during the period 2005 to 2015. This article describes the synthetic routes of these heterocycles that involve a Brønsted acid-promoted cyclization as a crucial step or Brønsted acids as co-catalysts with other transition metals.