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Synthesis of Alkyl‐Substituted Helianthrones and Mesonaphthobianthrone by Highly Regioselective Photocyclization of Bianthronylidenes
Author(s) -
Müller Uwe,
Enkelmann Volker,
Adam Martin,
Müllen Klaus
Publication year - 1993
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19931260523
Subject(s) - regioselectivity , chemistry , isomerization , alkyl , protonation , stereochemistry , double bond , photochemistry , organic chemistry , catalysis , ion
The synthesis of the novel alkyl‐substituted helianthrones 8a, c and mesonaphthobianthrone 9 by photocyclization of the corresponding bianthronylidenes 7a, b is described. Regioselectivity and scope of the photocyclizations of 7a and 7b depend on the substitution pattern. The structures of 7a and 8a have been established by X‐ray crystallography and indicate an isomerization about the central double bond of 7a in the photoreaction. The structures of the protonated species of 8a and 9 are elucidated, and their optical absorption and emission behavior is examined.