TFA-Catalyzed [3+2] Spiroannulation of Cyclobutanols: A Route to Spiro[cyclobuta[a]indene-7,1′-cyclobutane] Skeletons

A straightforward method for the synthesis of spiro[cyclobuta[a]indene-7,1 '-cyclobutane] derivatives from cyclobutanols has been developed via one-pot [3+2] spiroannulation. A series of new spiro[cyclobuta[a]indene-7,1 '-cyclobutane] derivatives are facilely synthesized in good yields under mild reaction conditions.