Azetidines are of particular interest in medicinal chemistry for their favorable properties, including increased resistance to oxidative metabolism and lower lipophilicity. The recent development of [2 + 2] reactions has significantly expanded the limited repertoire of methods for azetidine synthesis, but access to more complex architectures still requires further development. Herein, we report a visible-light-enabled intramolecular [2 + 2] cycloaddition of unactivated alkenes that proved previously unreactive to access tricyclic azetidines with 3D complex structures and high levels of saturation.

A method for the synthesis of highly substituted cyclopropanes via a quasi-Favorskii rearrangement is described. The method includes the combination two chemical transformations starting from α,α-dichlorocyclobutanones prepared via the [2 + 2] Staudinger ketene cycloaddition between either terminal- or cis-olefins and dichloroketene. First, α,α-dichlorocyclobutanones are reacted with organocerium reagents to afford the corresponding tertiary alcohols in good to excellent yields through a nucleophilic addition reaction that provided exclusively anti-products. Second, upon irreversible deprotonation, the tertiary α,α-dichlorocyclobutanols underwent a ring-contraction reaction (i.e., quasi-Favorskii rearrangement) to form structurally diverse cyclopropanes in moderate to good yields. The syn-stereoselectivity during the quasi-Favorskii rearrangement was evaluated using DFT analysis.

Since the first reports of their isolation, the meroterpenoids cochlearol A and B have attracted interest from the synthetic community for their unique structural features. This review describes the attempted and successful total syntheses of these natural products and provides a summary of the strategies developed in the years since their isolation.

Azetidines are of particular interest in medicinal chemistry for their favorable properties, including increased resistance to oxidative metabolism and lower lipophilicity. The recent development of [2+2] reactions has significantly benefitted the previously limited methods for azetidine synthesis, but access to more complex architectures still requires further development. Herein we report a visible-light enabled intramolecular [2+2] cycloaddition to access tricyclic azetidines with 3D complex structures and high levels of saturation.