Thermal [2+2]-cycloaddition between silylalkynes and allenylphenols followed by the nucleophilic addition of water: metal-free and economical synthesis of arylcyclobutenals

Herein, we report an unprecedented thermal [2 + 2]-cycloaddition between silylalkynes and allenylphenols to form an aromatizing cyclobutachromene intermediate, followed by the nucleophilic addition of water to yield functionalized arylcyclobutenals. This reaction is atom- and pot-economical because all the atoms contained in the starting material are retained in the final product, no other reactants are required, and it proceeds in one-pot.