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A Thioxanthone Sensitizer with a Chiral Phosphoric Acid Binding Site: Properties and Applications in Visible Light‐Mediated Cycloadditions
Author(s) -
Pecho Franziska,
Zou YouQuan,
Gramüller Johannes,
Mori Tadashi,
Huber Stefan M.,
Bauer Andreas,
Gschwind Ruth M.,
Bach Thorsten
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202000720
Subject(s) - thioxanthone , phosphoric acid , chemistry , hydrogen bond , intermolecular force , binding energy , enantioselective synthesis , photochemistry , catalysis , organic chemistry , molecule , photopolymer , polymerization , polymer , nuclear physics , physics
A chiral phosphoric acid with a 2,2’‐binaphthol core was prepared that displays two thioxanthone moieties at the 3,3’‐position as light‐harvesting antennas. Despite its relatively low triplet energy, the phosphoric acid was found to be an efficient catalyst for the enantioselective intermolecular [2+2] photocycloaddition of β‐carboxyl‐substituted cyclic enones (e.r. up to 93:7). Binding of the carboxylic acid to the sensitizer is suggested by NMR studies and by DFT calculations to occur by means of two hydrogen bonds. The binding event not only enables an enantioface differentiation but also modulates the triplet energy of the substrates.