A RhI/(S)-BINAP catalytic system is able to promote carbene alkyne metathesis and cascade this elemental step with an stereoselective reaction with allenes. An unusual carbene/allene reactivity is discovered that, through a formal addition of p-toluenesulfinic acid to a Rh-bound trimethylenemethane intermediate, affords 4-methylenetetrahydropyran compounds in good yields and excellent enantioselectivities

We are grateful for the financial support by the Spanish Ministry of Economy and Competitiveness (MINECO) (Project CTQ2014-54306-P) and the Generalitat de Catalunya (Project 2014-SGR-931, Xarxa de Referència en Química Teòrica i Computacional, ICREA Academia 2014 prize for M. S., and FI predoctoral grant to O.T.). The EU under the FEDER grant UNGI10-4E-801 has also funded this research