Difluoroboroxymolybdenum Fischer carbene complexes as precursors of acyl radicals: Dimerization and trapping with electron-deficient alkenes

Pentacarbonyl acyl molybdates 1 react with boron trifluoride to give difluo roboroxy Fischer carbene complexes 2, which undergo loss of the metal fragm ent at room temperature to form 1,2-diketones 3, 1,2-hydroxy ketones 4, or dimers 5 through a dimerization or decarbonylation-dimerization process of acyl radicals. Decomposition of 2 in the presence of electron-deficient alk enes 11 and 18 furnishes the two-, three-, and four-component coupling prod ucts 12, 13, 19, 20, and 21.