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Intramolecular photocycloadditions of 6,6′‐dimethyl‐4,4′‐polymethylenedioxy‐di‐2‐pyrones
Author(s) -
Shimo Tetsuro,
Ueda Shinichi,
Suishu Takaaki,
Somekawa Kenichi
Publication year - 1995
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570320304
Subject(s) - chemistry , intramolecular force , cycloaddition , adduct , methylene , selectivity , stereochemistry , ring (chemistry) , medicinal chemistry , organic chemistry , catalysis
Photosensitized reactions of 4,4′‐polymethylene‐di‐2‐pyrones 2b‐e afforded [2+2]‐cycloadducts 3‐5 , site‐selectively. The selectivity depended upon the methylene chain length. Namely, the three carbon chain gave a syn head‐to‐head adduct 3b at the 3,4‐position of the 2‐pyrone ring, the four to six carbon chains gave syn head‐to‐head adducts 4c‐e at the 5,6‐position and/or anti head‐to‐head adducts 5d,e at the 5,6‐position, respectively. The intramolecular cycloaddition mechanism was also explained from results calculated by means of PM3‐CI method.