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Greener Preparation of 5‐Ethyl‐4a‐hydroxyisoalloxazine and Its Use for Catalytic Aerobic Oxygenations
Author(s) -
Oonishi Takahiro,
Kawahara Takayuki,
Arakawa Yukihiro,
Minagawa Keiji,
Imada Yasushi
Publication year - 2019
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201801865
Subject(s) - chemistry , catalysis , redox , flavin group , environmentally friendly , alkyl , combinatorial chemistry , molecular oxygen , inert , organic chemistry , cofactor , enzyme , ecology , biology
Isoalloxazine ring systems are found in flavin cofactors in nature, and the simulation of their redox catalyses is an important task for developing sustainable catalytic oxidation reactions. Although 5‐ethyl‐4a‐hydroxyisoalloxazines are among the most promising candidates as catalyst for such purposes, the use of them for laboratorial as well as industrial synthetic chemistry has so far been quite limited presumably due to the lack of their preparation methods readily, safely, and inexpensively available. In this communication, we introduce an environmentally benign and practical preparation of 5‐ethyl‐4a‐hydroxy‐3,7,8,10‐tetramethylisoalloxazine ( 1Et OH ) from 3,7,8,10‐tetramethylisoalloxazine ( 1 ), in which conventional synthetic requirements, including (i) operations under inert conditions, (ii) risky or expensive chemicals, and (iii) isolation of labile intermediates, have all been dissolved. In addition, we have presented that 1Et OH could be an effective catalyst for Baeyer–Villiger oxidation as well as sulfoxidation with molecular oxygen (O 2 ) as a terminal oxidant under suitable conditions, which is the first report on aerobic oxygenations catalyzed by 5‐alkyl‐4a‐hydroxyisoalloxazines.