Solvent-free C–H alkynylation of azulenes

Abstract

A solvent-free coupling of azulenes with 1-haloalkynes and 1-halopolyynes has been developed. 1-Haloalkynes were used as substrates and the reaction needs only simple grinding of substrates in a mortar with basic Al₂O₃ without solvents or precious metal catalysts. The reaction works for longer 1-halopolyynes as well and direct introduction of a linear carbon chain up to (CC)₄ is possible giving an easy access to azulene end-capped sp-hybridised carbon molecular wires. Finally, further reactivity of the resulting azulenes was tested and two butadiynyl derivatives were transformed into the corresponding thiophenes.