Formation of an air-stable diborane via a stepwise BH3 addition of pyrido[1,2-a]isoindole with H2 evolution

A novel and air-stable organo(hydro)diborane featuring a five-membered aryl ring supported bridging B-C-B three-centre-two-electron (3c-2e) bond has been reported. Pyrido[1,2-asoindole was found to undergo a stepwise BH 3 addition reaction, during which a mono-BH3 adduct was formed from a electrophilic addition at the C-gamma in pyrido[1,2-asoindole. A molecule of hydrogen was eliminated throughout the second step of addition reaction. DFT calculations indicate that the H-2 evolution is concerted to the second BH3 addition rather than forming B=C before the second BH3 attack.

Automated summary

An air-stable organo(hydro)diborane with a five-membered aryl ring supported bridging B-C-B three-centre-two-electron (3c-2e) bond has been reported, showing a stepwise BH3 addition reaction with pyrido[1,2-asoindole and elimination of a hydrogen molecule during the second step of addition. DFT calculations suggest that the H-2 evolution is concerted with the second BH3 addition.