Transition metal-free photodecarboxylative amination of redox-active esters with diazirines

Due to the prevalence of nitrogen-containing compounds in medicine, materials, and related fields, the search for general, mild methods for electrophilic amination remains an area of intense research. Diazirines have been recently demonstrated to serve as electrophilic amination reagents that afford diaziridines, versatile heterocycles that are readily transformed into amines, hydrazines, and a variety of nitrogen-containing heterocycles. Here we report the phosphine-mediated, photodecarboxylative amination of redox-active esters with diazirines. This method is transition metal-free, uses inexpensive photoactivators under mild conditions, and offers a significantly enhanced scope and yields for primary redox-active esters. Furthermore, the stability of diazirines to blue light (456 nm) is demonstrated, paving the way for further research into other photochemical amination methods with these unique heterocycles.

Theoretical and Experimental Insights into the Tandem Mannich—Electrophilic Amination Reaction: Synthesis of Safirinium Dyes

Isoxazolo[3,4-b]pyridin-3(1H)-ones are ‘spring-loaded’ compounds that quantitatively react with iminium salts derived from formaldehyde and secondary amines to yield fluorescent Safirinium dyes. The mechanism and energetics of the above tandem Mannich–electrophilic amination reaction have been investigated experimentally and using theoretical methods. The hybrid B3LYP functional with GD3 empirical dispersion and range-separated hybrid functional ωB97XD, both combined with a PCM model, were applied to acquire the energetic profiles of the studied reaction with respect to the structure of secondary amine and isoxazolone used. Diastereoselectivity of the tandem reactions involving iminium salt derived from L-proline has been rationalized theoretically by means of density functional theory calculations.