Tandem catalysis in the polycyclisation of dienes to produce multi-substituted tetrahydrofurans

A new catalytic protocol has been established by using two separate oxidation reactions, catalysed by osmium, in tandem. Control of the pH and oxidation state of the metal is crucial in controlling this new sequence, which begins with a tethered aminohydroxylation reaction (Os(VIII) is active) and is followed by an oxidative cyclisation under acidic conditions (Os(VI) is active). The result of this work is an extremely quick route (five steps from commercially available materials) to complex THF rings containing an adjacent oxazolidinone and four new stereogenic centres.