Thermal [2+2]-Cycloaddition between Silyl Alkynes and Allenyl Phenols 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 the aromatizing cyclobutachromene intermediate, followed by the nucleophilic addition of water to yield functionalized arylcyclobutenals. This reaction is atom- and pot-economical because all atoms contained in the starting material were retained in the final product, no other reactants are required, and it proceeds in one-pot.