Cross-Metathesis/Isomerization/Allylboration Sequence for a Diastereoselective Synthesis of Anti-Homoallylic Alcohols from Allylbenzene Derivatives and Aldehydes

We describe a highly diastereoselective approach to anti-homoallylic alcohols from allylbenzene derivatives and aldehydes. The strategy is based on a cross-metathesis/isomerization/allylboration sequence catalyzed successively by ruthenium and iridium. This methodology provides another way to access this class of compounds, which leads to the preparation of hitherto-unknown homoallylic alcohols without the requirement to control the stereochemistry of the 1-alkenyl boronate intermediates. Our study towards an enantioselective version of this sequential reaction is also reported.