Synthesis 2001(8): 1248-1252
DOI: 10.1055/s-2001-15055
PAPER
© Georg Thieme Verlag Stuttgart · New York

1,3-Dimethyl-2-phenylbenzimidazoline (DMPBI)-Acetic Acid: An Effective Reagent System for Photoinduced Reductive Transformation of α,β-Epoxy Ketones to β-Hydroxy Ketones

Eietsu Hasegawa*, Naoki Chiba, Aiko Nakajima, Kumiko Suzuki, Akira Yoneoka, Kazuki Iwaya
Department of Chemistry, Faculty of Science, Niigata University, Ikarashi-2 8050, Niigata 950-2181, Japan
Fax: +81(25)2626116; e-Mail: ehase@sc.niigata-u.ac.jp;
Further Information

Publication History

Received 29 January 2001
Publication Date:
24 September 2004 (online)

Abstract

A combination of 1,3-dimethyl-2-phenylbenzimidazoline (DMPBI) and acetic acid has been utilized for photoinduced reductive transformation of α,β-epoxy ketones to β-hydroxy ketones. Study on photoreactions using several proton donors revealed that acetic acid is superior to other proton donors such as HCl, p-TsOH, MeOH, and water. 1,3-Dimethyl-2-phenylbenzimidazolium was produced in the reaction with acetic acid while N-benzoyl-N,N′-dimethyl-o-phenylenediamine was formed in aqueous solvents. When THF solutions containing aryl carbonyl possessing α,β-epoxy ketones and DMPBI and acetic acid were irradiated (λ > 280 nm), β-hydroxy ketones were isolated in good to excellent yields. Photosensitized conditions (λ > 340 nm) were employed for the reactions of alkyl carbonyl possessing α,β-epoxy ketones.

11

Spectral and elemental analysis data of 1b, 1d, 1k, 1l and 2b, 2d, 2k, 2l were reported as Supplementary Material of reference 3k.