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Novel transformations of two kinds of chlorinated photo [2 + 2] cycloadducts of 2‐pyrone‐5‐carboxylate
Author(s) -
Shimo Tetsuro,
Date Kenichi,
Somekawa Kenichi
Publication year - 1992
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.5570290217
Subject(s) - chemistry , carboxylate , cyclobutene , medicinal chemistry , pyran , cycloaddition , ene reaction , bicyclic molecule , stereochemistry , organic chemistry , ring (chemistry) , catalysis
Novel reactions of 7,7‐dichloro‐ and 7,7,8‐trichloro‐3‐oxo‐2‐oxabicyclo[4.2.0]oct‐4‐ene‐6‐carboxylates 5 with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) in alcohol gave pyrano[4,3‐ b ]pyran‐2,5‐diones 8 via ( Z )‐(2 H ‐pyran‐2‐on‐3‐yl)butenoates 7. On the other hand, the same treatment of 7,7,8‐trichloro‐2‐oxo‐3‐oxabicyclo‐[4.2.0]oct‐4‐ene‐5‐carboxylate 6b afforded 2‐oxo‐3‐oxabicyclo[4.2.0]oct‐4,7‐diene‐5‐carboxylate 14 via cyclobutene formation and S N 2′ displacement by attack of the alkoxy anion.
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