Rhodium(i)-catalysed intermolecular alkyne insertion into (2-pyridylmethylene)cyclobutenes.

Cyclobutenes with 2-pyridylmethylene groups at the 3 position underwent an intermolecular alkyne insertion reaction in the presence of a rhodium(i) catalyst at 170 °C to afford substituted benzenes. Among the different 2-pyridylmethylene groups examined, 3-methyl-2-pyridyl derivatives showed superior activity and readily coupled with various alkynes, including sterically demanding, heteroaromatic and terminal alkynes.