Abstract

The hexacarbonyldicobalt complexes of propargylic cations are generated readily, predominantly from alkynedicobalt complexes bearing propargylic leaving groups. These cations have both good stability and reactivity, and enter into reaction with a wide range of carbon- and heteroatom-based nucleophiles in a reliable manner; these are widely known as Nicholas reactions. In conjunction with the ready incorporation and removal of the dicobalt unit, these reactions have been employed extensively in total synthesis.