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Cyclohexa‐1,2,4‐triene from 1‐Bromocyclohexa‐1,4‐diene
Author(s) -
Christl Manfred,
Groetsch Stefan
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(200005)2000:10<1871::aid-ejoc1871>3.0.co;2-3
Subject(s) - chemistry , diene , furan , benzophenone , medicinal chemistry , styrene , bromide , deprotonation , hydrogen bromide , dehydrogenation , organic chemistry , ion , bromine , catalysis , natural rubber , copolymer , polymer
1‐Bromocyclohexa‐1,4‐diene ( 3 ) was prepared from trans ‐4,5‐dibromocyclohexene by elimination of hydrogen bromide. Treatment of a solution of 3 in furan or 2,5‐dimethylfuran with KO t Bu afforded the tetrahydroepoxynaphthalenes 4 and 5 , respectively. The structure of these products is evidence for the title cycloallene (isobenzene 1 ) being the reactive intermediate. The compounds 4 and 5 were dehydrogenated by DDQ to the known dihydroepoxynaphthalenes 6 and 7 , respectively. These conversions unambiguously confirm the structures of 4 and 5 . In pure styrene, 3 was not attacked by KO t Bu, and only upon the addition of 18‐crown‐6 did a reaction occur. This reaction did not, however, furnish the known [2+2] cycloadduct 9 of styrene and 1 , but, instead, a small amount of 1,2‐diphenylethane ( 8 ) was formed. In agreement with this finding, the conjecture that 1 was deprotonated to give the phenyl anion was confirmed by the treatment of a solution of 3 and benzophenone in THF with KO t Bu, which resulted in the formation of triphenylmethanol.