Photoinduced Temperature-Regulated Selective Carbene C-H Insertion for the Synthesis of Functionalized Spiro-β-lactones and -lactams.

A temperature-regulated catalyst-free photoinduced selective carbene C-H insertion strategy was realized to efficiently synthesize spiro--lactones and -lactams, which hold considerable promise in drug discovery programs. The reaction shows broad applicability across a range of α-diazo esters and amides with various ring sizes and substituents and has been demonstrated to successfully achieve the late-stage spirocyclization of natural/bioactive compounds. The obtained products could be transformed into spiro-oxetanes, -azetidines, and -cyclopropanes, privileged scaffolds with broad utility in medicinal chemistry.

The Dowd-Beckwith Reaction: History, Strategies, and Synthetic Potential.

Ring-expansion strategies are valuable synthetic tools that take benefit of existing ring structures and evade the unfavorable enthalpic-and entropic effects that arise with end-to-end cyclizations. One potentially important class of such reactions is the Dowd-Beckwith reaction, the ring-expansion of ketones via alkoxy radicals. The exciting advancement in this research area is starting to show its potential, as demonstrated by applying this methodology in strategy-level bond formation to synthesize complex natural products.