The Rearrangement and Nucleophilic addition of Donor-Acceptor Cyclobutane: Novel Methodologies to Access δ-Lactones and Ring-Opened Products

Donor-acceptor (D-A) cyclobutanes are a well recognized building block in synthetic organic chemistry thanks to their unique reactivity. A variety of synthetic methodologies such as cycloaddition, rearrangement, and ring-opening addition of D-A cyclobutanes have been reported. Among them, the rearrangement reactions of D-A cyclobutanes have attracted less interest compared with other methodologies as they too often require extreme reaction conditions. To further explore the rearrangement reactions of D-A cyclobutanes, in this work a ring expansion rearrangement reaction of D-A cyclobutanes analogous to the Cloke–Wilson reaction of cyclopropanes was examined. By exploiting the solvent effect in a Brønsted acid system, we successfully acquired the target lactone products in moderate yield (49–65%). The current work also demonstrated that alkoxy-activated cyclobutanes could undergo a ring-opening and nucleophilic addition to generate nucleophilic substituted products under mild condition with good yield (58–98%). These products are good scaffolds to access cyclic compounds that are commonly found in natural products