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Photochemical Behavior of Doubly Bridged Dewar Benzenes – Synthesis of Prismanes
Author(s) -
Gleiter Rolf,
Ohlbach Frank,
Haberhauer Gebhard,
Irngartinger Hermann,
Oeser Thomas
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619961020
Subject(s) - chemistry , alkyl , benzene , yield (engineering) , irradiation , hexa , photochemistry , medicinal chemistry , crystallography , polymer chemistry , stereochemistry , organic chemistry , materials science , physics , nuclear physics , metallurgy
In this paper we report on the photochemistry of Dewar benzenes bridged at the 1,4‐ and 5,6‐positions and substituted at the 2,3‐positions. It was found that simple alkyl substitution leads to prismanes only to a minor extent. Introduction of phenyl groups into the 2‐ or 2,3‐positions gives the corresponding doubly bridged prismanes in yields up to 80% Pentamethylene‐bridged bis‐Dewar benzenes 19 rearrange upon irradiation to 22 . Irradiation of the doubly bridged Dewar benzene derivatives with one ester group at the 5‐position does not yield isolable products. However, introduction of one tert ‐butylsulfonyl group such as 30–33 gives almost quantitative yields of isolable prismanes if pentamethylene or hexamethylene bridges are used. The nonbridged species, 2‐ tert ‐butylsulfonyl‐1,4,5,6‐tetramethylbicyclo[2.2.0]hexa‐2,5‐diene ( 44 ), aromatizes upon irradiation into 1‐( tert ‐butylsulfonyl)‐2,3,4,5‐tetramethylbenzene ( 45 ). In contrast to the pentamethylene‐bridged monosulfone 47 , the corresponding disulfone 38 undergoes no photochemical reaction. This could be explained by the X‐ray structure, which reveals a strong interaction between one of the tert ‐butyl groups and the pentamethylene chain bridging the double bond in 38 .