Palladium-catalyzed [3C + 2C + 2C] cycloaddition of enynylidenecyclopropanes: efficient construction of fused 5-7-5 tricyclic systems
作者:Gaurav Bhargava、Beatriz Trillo、Marisel Araya、Fernando López、Luis Castedo、José L. Mascareñas
DOI:10.1039/b919258a
日期:——
We report a Pd-catalyzed intramolecular [3C + 2C + 2C] cycloaddition between alkylidenecyclopropanes, alkynes and alkenes. The method provides synthetically relevant 5-7-5 tricyclic structures, with good chemoselectivity and complete diastereoselectivity.
to afford bicyclic pyridines. Careful screening of nitrile components revealed that a C[triple chemical bond]C triple bond or heteroatom substituents, such as methoxy and methylthio groups, proved to act as the coordinating groups, whereas C==C or C==O doublebonds and amino groups failed to promote cycloaddition. This suggests that coordinating groups with multiple pi-bonds or lone pairs are essential
The RhI-catalyzed intramolecular [5+2–2]-type cycloisomerization of allene–allenylcyclopropanes was developed. In this reaction, ethylene was liberated from the cyclopropane ring to afford the 1,5,6,7-tetrahydroazulene skeletons.
The reaction of diyne arylsulfonyl hydrazone substrates under rhodium(I)/BINAP catalysis gives access to sulfonated azacyclic frameworks in a highly enantioselective manner. This new cascade process considerably increases the molecular complexity by generating two CC bonds, one CS bond, and one CH bond. Theoretical calculations, competitive experiments, and deuterium labeling have jointly been used