Facile Synthesis of Tetrahydrofurans from Cycloadditions of Vinylidenecyclopropanes with Aldehydes and Further Tunable Transformations for the Construction of Furan, Indene, and Benzo[c]fluorene Derivatives

The cycloadditions of vinylidenecyclopropanes with aldehydes for the synthesis of tetrahydrofurans are detailed in this paper. The obtained polysubstituted tetrahydrofurans could serve as versatile intermediates to selectively produce furan, indene, and benzo[c]fluorene derivatives depending on the substituents at the tetrahydrofurans' rings and the varied reaction conditions, which clearly exhibit insights into the synthetic applications of tetrahydrofurans. The scope, limitations, and mechanisms of these transformations have been discussed in detail. Attractively, these cycloadditions of vinylidenecyclopropanes with aldehydes and the further transformations of the cycloadducts provide an efficient protocol for the construction of various medium- and large-size ring-fused tetrahydrofuran, furan, and benzo[c]fluorene derivatives.