Highly stereoselective, molybdenum-catalysed [6 + 2]-cycloadditions of α,β-unsaturated ketones to cyclohepta-1,3,5-triene

Cycloheptatriene undergoes highly peri- and diastereo-selective [6 + 2]-cycloaddition reactions with 1-oxadienes in the presence of catalytic amounts of η4-oxadiene molybdenum complexes under mild conditions; the stereochemistry of a cycloadduct derivative 6 and that of the corresponding tungsten oxadiene complex suggests that cycloheptatriene attacks the oxadiene from the metal free side.