Conditions have been developed that enable intermolecular Dötz benzannulations to be carried out under extremely mild conditions, using 1,2-DCE as the reaction solvent and without the requirement for any additional reaction promoters. The new protocols, at temperatures close to ambient, have been applied successfully to a range of internal and terminal alkynes with a series of aryl and alkenyl carbene complexes, resulting in good to high yields of the benzannulation products. The developed conditions did, however, return lower benzannulation yields when utilised with the traditionally more troublesome 2-furyl carbene complex. It was found that increased reaction temperatures in 1,2-DCE did deliver high yields for the processes with this heteroaryl species.
- dotz benzannulation