Premium
Asymmetric Synthesis Involving Reversible Photodimerization of a Prochiral Flavonoid Followed by Crystallization
Author(s) -
Ishikawa Hiroki,
Uemura Naohiro,
Yagishita Fumitoshi,
Baba Nozomi,
Yoshida Yasushi,
Mino Takashi,
Kasashima Yoshio,
Sakamoto Masami
Publication year - 2017
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.201701457
Subject(s) - chemistry , dimer , racemization , crystallization , monomer , derivative (finance) , yield (engineering) , photochemistry , crystallography , stereochemistry , organic chemistry , polymer , materials science , financial economics , economics , metallurgy
Asymmetric synthesis involving photochemical dimerization of a prochiral flavonoid derivative in solution without any chiral source was achieved. Irradiation of ethyl 6‐bromochromonecarboxylate in solution efficiently gave a C 2 ‐chiral anti ‐head‐to‐head dimer in excellent chemical yield with good quantum efficiency ( Φ 365 = 0.15). X‐ray crystallographic analysis revealed that the dimer crystallized as a conglomerate of C 2 space group. The crystalline dimer precipitated upon irradiation of the monomer in solution, and indirect racemization of the dimer through a reversible photoreaction in solution and selective crystallization simultaneously occurred to give the C 2 ‐chiral dimer in optically active form with up to 80 % ee . Optically active photoproducts could be obtained by simply irradiating achiral materials in solution without an external chiral source.