Anion effect of 5-ethylisoalloxazinium salts on flavin-catalyzed oxidations with H2O2. Issue 40 (5th October 2016)

• Record Type: Journal Article
• Authors: Iida, Hiroki; Ishikawa, Tatsuro; Nomura, Keisuke; Murahashi, Shun-Ichi
• Is Part Of: Tetrahedron letters. Volume 57:Issue 40(2016)
• Page Start: 4488
• Page End: 4491
• Publication Date: 2016-10-05
• Subjects: Flavin -- Oxidation -- Organocatalyst -- Isoalloxazinium salt -- Anion effect; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tetlet.2016.08.076
• Languages: English
• ISSNs: 0040-4039

Abstract

Graphical abstract: Highlights: The anion effect of isoalloxazinium salts on the catalytic activity is investigated. The anions forming stronger conjugated acids accelerate the H2 O2 oxidation. The riboflavin-based triflate salt is an excellent catalyst for diverse oxidations. Abstract: The anion effect of the 5-ethylisoalloxazinium salts on their catalytic activity was investigated for the oxidation of sulfide with aq H2 O2 in order to design more practical and safer flavinium salt catalysts that can replace the conventional perchlorate salt. The anions forming stronger conjugated acids were found to accelerate the catalytic sulfoxidation. The riboflavin-derived isoalloxazinium triflate salt was chosen as a readily accessible flavin with an efficient catalytic activity. In fact, the isoalloxazinium triflate1b is an excellent organocatalyst for the chemoselective oxidations of a sulfide to a sulfoxide, Bayer–Villiger reaction of a cyclobutanone to a γ-butyrolactone, Dakin reaction of an arylaldehyde to a phenol, and oxidation of an aldehyde to a carboxylic acid using aq H2 O2 as a terminal oxidant under mild conditions.