Oxidative intramolecular [4 + 2]cycloaddition of silylene-protected 2-pyridone derivatives—a short and efficient synthesis of the DEF-ring of fredericamycin A
Oxidative intramolecular [4 + 2]cycloaddition of silylene-protected 2-pyridone derivatives—a short and efficient synthesis of the DEF-ring of fredericamycin A
A linear approach to the totalsynthesis of racemic fredericamycin A (1) through the oxidative intramolecular [4 + 2] cycloaddition of a (phenylthio)acetylene-cobalt complex is described, which is applicable for the asymmetric totalsynthesis of naturally occuring 1. The highlight of this work is the aromaticPummerer-typereaction with 1-ethoxyvinyl chloroacetate, which effects the introduction of