Excellent stereocontrol in intramolecular Buchner cyclisations and subsequent cycloadditions; stereospecific construction of polycyclic systems

Highly diastereoselective rhodium(II) acetate-catalysed intramolecular addition of α-diazo ketones to aromatic rings to form the azulenones 3 has been achieved; the norcaradiene form of 3 undergoes efficient stereospecific cycloaddition with phenyltriazolinedione, in either a stepwise or a tandem process, leading to the pentacyclic systems 4 as a single diastereomer in each case.