Open AccessRapid Photoracemization of Chiral Alkyl Aryl Sulfoxides
Author(s) -
Kosho Makino,
Kumi Tozawa,
Yūki Tanaka,
Akiko Inagaki,
Hidetsugu Tabata,
Tetsuta Oshitari,
Hideaki Natsugari,
Hideyo Takahashi
Publication year - 2021
Publication title -
journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.2
H-Index - 228
eISSN - 1520-6904
pISSN - 0022-3263
DOI - 10.1021/acs.joc.1c02320
Subject(s) - racemization , enantiopure drug , alkyl , aryl , chemistry , sulfoxide , photosensitizer , photoisomerization , tetrafluoroborate , medicinal chemistry , organic chemistry , photochemistry , enantioselective synthesis , isomerization , catalysis , ionic liquid
The photoracemization of chiral alkyl aryl sulfoxides with a photosensitizer has not been sufficiently investigated thus far. Therefore, in this study, a rapid photoracemization reaction of enantiopure alkyl aryl sulfoxides using 1 mol % 2,4,6-triphenylpyrylium tetrafluoroborate (TPT + ) was developed. Various substitution patterns were tolerated and every racemization reaction proceeded extremely fast ( k 2 = 1.77 × 10 4 -6.08 × 10 1 M -1 s -1 , t 1/2 = 0.4-114 s). Some chiral sulfoxides with easily oxidizable functional groups are not appropriate for this photoisomerization. The electrochemical potentials of the functional groups, determined via cyclic voltammetry, are useful for predicting the reactive or nonreactive groups in this photoracemization reaction. A theoretical study was conducted to clarify the sp 2 -like nature of S of the sulfoxide cation radical, which makes photoracemization easier.