An unexpected one step domino conversion of TMS-alkynes to protected ketones in 4-chromenone system

An unexpected metal-free high yielding one step domino procedure for TMS-deprotection and simultaneous conversion of resulting alkynes to protected carbonyls (ketals) in 4-chromenone systems is reported. A mechanistic rationale involving an allene intermediate is also proposed based on dynamic NMR and mass spectra.