Rearrangement of a carboxy-substituted spiro[4.4]nonatriene to annulated fulvenes through a Pd(ii)-mediated 1,5-vinyl shift

A novel synthesis of aryl-substituted, enantioenriched fulvenes from an oxidative Heck cascade and rearrangement of a carboxy-substituted spiro[4.4]nonatriene is disclosed. Mechanistic investigations with density functional theory (DFT) calculations and empirical results support the net transformation occurring through a novel Pd(ii)-mediated 1,5-vinyl shift from a vinyl-palladium intermediate that terminates with protodepalladation. This spiro-to-fused bicycle conversion tolerates a range of electron-rich and deficient arylboronic acids to give a range of mono- and diaryl substituted annulated fulvenes in moderate to good yields and enantiomeric ratios. Overall, this work connects two classes of molecules with a rich history in physical organic chemistry.

Automated summary

A novel synthesis method for aryl-substituted, enantioenriched fulvenes from an oxidative Heck cascade and a rearrangement of a carboxy-substituted spiro[4.4]nonatriene is disclosed. Mechanistic investigations using density functional theory (DFT) calculations and empirical results show that the net transformation occurs through a Pd(ii)-mediated 1,5-vinyl shift from a vinyl-palladium intermediate, which terminates with protodepalladation. This method tolerates a range of electron-rich and deficient arylboronic acids and provides moderate to good yields and enantiomeric ratios of mono- and diaryl substituted annulated fulvenes.