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Cycloadditions of Allyl Cations, 29. Acid Catalyzed Reactions of 2,3‐Dimethyl‐3‐penten‐2‐ol and Cyclopentadiene in Two Phases. Formation of Seven‐ and Five‐membered Rings
Author(s) -
Hoffmann H. M. R.,
VathkeErnst Heidrun
Publication year - 1981
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19811140820
Subject(s) - chemistry , bicyclic molecule , cyclopentadiene , medicinal chemistry , silver nitrate , diene , pentane , sulfonic acid , yield (engineering) , ring (chemistry) , stereochemistry , catalysis , organic chemistry , natural rubber , materials science , metallurgy
2,3–Dimethyl‐3‐penten‐2‐ol (3) and cyclopentadiene were stirred in dilute aqueous sulfonic acid/pentane, giving 2,3,4,4‐tetramethylbicyclo[3.2.1]octa‐2,6‐diene (4) , the epimeric 3‐methyl‐ene isomers 5a, b and, for the first time, also a five‐membered ring, namely 2,3,4,4‐tetramethylbicyclo[3.3.0]octa‐2,6‐diene (6) in 69 – 73% overall yield. The major bicyclic diene 4 was conveniently isolated as crystalline silver nitrate complex (C 12 H 18 ) 2 ·AgNO 3 (41 – 44%). In a modified approach the two phase reaction was carried out at 0°C, the resulting alcohols were separated by chromatography and cyclized at 50°C, giving an increased proportion of the thermodynamically more stable, novel [3.3.0] bicyclic isomer 6 (4:6 = 2.6:1)