Novel Concepts in Directed Biaryl Synthesis, 68 Enantioselective Organic Syntheses Using Chiral Transition Metal Complexes, 9 Atropo-Diastereoselective Ring Opening of Biaryl Thionolactones Using [CpRu{(S,S)-CHIRAPHOS}] + as a Chiral Auxiliary

Photolytically-induced reactions of chromyl chloride with acetylene and but-2-yne (dimethylacetylene) in low-temperature argon matrices yield end-on ketene and dimethylketene complexes of O=CrCl2, respectively. The product formation probably results from an electrophilic attack of a Cr=O linkage on the C=C triple bonds, leading to radical-like transition states or intermediates, which subsequently rearrange through 1,2-H or 1,2-methyl shifts. Consequently, allene is attacked at its central carbon and the allyl radical thus generated undergoes subsequent ring-closure to give a cyclopropanone complex of O=CrCl2.