Photoinduced Synthesis of Bisphosphinated Quinoxalines via Radical Cyclization ofo‐Diisocyanoarenes with Diphosphines

Abstract

The cycloaddition reaction of o-diisocyanoarenes with interelement compounds under light is a very important reaction system to clarify whether this reaction proceeds by radical cyclization or by aza-Bergman cyclization. In this study, a series of diphosphines with phosphorus-phosphorus single bonds were selected as interelement compounds, and their cycloaddition reactions with o-diisocyanoarenes under light were investigated in detail to achieve a novel photo-induced synthesis of bisphosphinated quinoxalines via the radical cyclization pathway. In addition, the photoinduced reaction of diphosphines with isocyanides having o-functional groups such as cyano and ethenyl groups allowed us to elucidate the reaction pathway and product selectivity of this bisphosphination. Furthermore, the one-pot synthesis of Pd II -quinoxaline complex was successfully achieved by applying the developed reaction.

Transition-Metal- and Photocatalyst-Free Photoinduced Formation of Carbon–Pnictogen (–N, –P) Bonds

“…62 Scheme 22 Phosphinylation of unactivated ethers 61 Recently, Ogawa and Yamamoto reported the photoinduced synthesis of bisphosphinated quinoxalines through reactions between o-diisocyanoarenes and diphosphines, all without the need for any photocatalyst. 63 A thorough mechanistic study suggested a process involving radicalmediated cyclization.…”

Iodine‐Catalyzed One‐pot Formation of Phosphorus‐Heteroatom Bonds from Stable Diphosphines in Air

“…[20] Based on this background, we have energetically developed straightforward synthetic methods of phosphorus-heteroatom compounds and their application to the functionalization of carbon-carbon unsaturated compounds via radical reactions and transition-metal-catalyzed reactions. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] In particular, we have found that diphosphines containing phosphorusphosphorus single bonds can efficiently react with organic dichalcogenides to form the corresponding phosphorus-chalcogen interelement compounds. [32] Among a variety of diphosphines, tetraphenyldiphosphine disulfide, Ph 2 P(S)-P(S)Ph 2 1, is quite stable to air and moisture.…”

Palladium-Catalyzed Hydrophosphination of Terminal Alkynes with Diphenylphosphine Oxide in the Presence of Tetraphenyldiphosphine Monoxide

“…This is because strict degassing and dehydration techniques for treatment of air- and moisture-sensitive organophosphorus compounds were insufficient at that time. After that, we have developed a series of addition reactions of phosphorus compounds, especially diphosphine analogues, to unsaturated bonds and have accumulated expertise in the handling of organophosphorus compounds …”