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Photochemistry of 2,2‐Dimethyl‐2 H ‐Furo[3,4‐ b ]Pyran‐4,7(3 H , 5 H )‐Dione
Author(s) -
Lau Sabine,
Margaretha Paul
Publication year - 1988
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19880710224
Subject(s) - chemistry , alkene , irradiation , pyran , photochemistry , undecane , medicinal chemistry , structural isomer , cleavage (geology) , stereochemistry , organic chemistry , catalysis , nuclear physics , fracture (geology) , engineering , physics , geotechnical engineering
Irradiation (λ > 340 nm) of the title compound 2a in t ‐BuOH affords 3,3,10,10‐tetramethyl‐2,8‐dioxatricyclo‐[4.3.2.0 1,6 ]undecane‐5,9‐dione (3) via photoextrusion of 2‐methylpropene and subsequent photocycloaddition of 2a to the alkene. The same regioisomer 3 is formed selectively and in much higher yields on irradiating 2a in the presence of excess 2‐methylpropene. Irradiation of 3 (λ = 300 nm) in t ‐BuOH in the presence of the same alkene gives a 6:1 mixture of spirooxetanes 7a and 7b but not α‐cleavage products. In 2‐propanol, 2a is photoreduced to a 2:1 mixture of diastereoisomeric hydrodimers 9 .