A Major Breakthrough in the Use of Alkoxycarbene Complexes of Chromium and Tungsten for the Synthesis of Elaborate Organic Compounds: Dihydropyridine Induced Reductions and Cascade Insertion Reactions

Alkoxy (alkyl)carbene complexes of tungsten and chromium react with dihydropyridine and N-methyldihydropyridine to give respectively pyridinium ylid complexes and N-methylpyridinium tungstates and chromates. These two types of complexes can be used, for the former, as cyclopropanation reagents, for the latter, as unprecedented initiators of cascade multiinsertions of olefins, alkynes and CO. These insertions lead to elaborate polycyclic compounds.