Synthesis of Photochromic Phosphines by Pd‐Catalyzed Annulation Reaction of Alkynes Bearing Phosphinyl Substituent with a Silacyclopropene

Abstract

The synthesis of phosphines with light controlled basicity is presented in this study. A methodological approach for the preparation of these unconventional photochromic phosphines based on a dithienylethene organic moiety is reported. It relies on the palladium‐catalyzed annulation of alkynyl phosphines in the presence of a 2,3‐Dithienylsilacyclopropene. Accordingly, a diphenyphosphino moiety is connected to the organic photochrome thanks to different linkers. Their influence on the photochromism and on the phosphinyl group basicity is studied and evaluated based on experimental an NMR descriptor as well as DFT calculations.

Synthesis of Halogenated Dibenzo[1,2,6]triazonines and Late-Stage Functionalization of the Triazonine Ring

“…In our previous paper, 13 we have shown that the parent Nprotected dibenzo [1,2,6]triazonines are available via a reaction sequence that involves formation of the diazo unit as the final step. This step can be carried out either by reductive cyclization of bis(o-nitrobenzyl)amines or by oxidative cyclization of bis(o-aminobenzyl)amines.…”

“…This last method provided (E)-3,8-diiodo-12-tosyl-12,13-dihydro-11H-dibenzo[c,h]-Scheme 1. Synthesis of (E)-3, h][1,2,6]triazonine (E)-4a [1,2,6]triazonine 4a in 35% yield, while reductive conditions led to 4a as a complex mixture with dehalogenated products.…”

“…In this context, halogenated triazonines might be key synthetic intermediates as far as they will enable introduction of a huge variety of substituents, including functional groups. Therefore, in this article, we report methods to access mono-and dihalogenated dibenzo [1,2,6]triazonines.…”

“…Azobenzenes are ubiquitous, reversible photoswitches 1 that have driven considerable attention as optical and mechanical devices in supramolecular 2 and materials chemistry, 3 catalysis, 4 and biomedical applications, 5 among others. 6 Their photophysical properties and photoswitch efficiency have been modulated, expanded, and enhanced by extensive tuning of their substitution patterns.…”

“…Although seven-membered cyclic azobenzene diazepines (III) have been known for decades, 9 extensive investigations on their photophysical behavior have been reported only recently, showing that the E form is especially unstable with a lifetime in the millisecond range. 10 Similarly, the photochemical isomerization of dibenzo [c,h][1,2]diazonine (IV) 11 and dibenzo [c,g][1,5,6]-thiadiazonine (V) 12 has been disclosed starting from 2018 and cyclic azobenzenes based on [1,2,6]triazonine scaffolds (VI) have been introduced in 2021 by our group. 13 In the diazonine series, the nature of the bridging chain subtly controls the geometrical features.…”