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Intramolekulare Diels‐Alder‐Additionen in 6‐(But‐3‐enyl)‐6‐methyl‐cyclohexa‐2,4‐dien‐1‐on‐Systemen; eine neue Synthese von Twistanderivaten
Author(s) -
Greuter H.,
Schmid H.
Publication year - 1972
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.19720550713
Subject(s) - chemistry , methylene , alkylation , yield (engineering) , medicinal chemistry , toluene , dimethyl ether , ether , organic chemistry , catalysis , materials science , metallurgy
Alkylation of the sodium salt of mesitol with 2‐bromomethyl‐buta‐1,3‐diene ( 7 ) in benzene and subsequent refluxing of the reaction mixture gave 7% 2‐methylene‐3‐butenyl‐mesitylether ( 8 ), 12% 5‐methylene‐1,3,8‐trimethyl‐tricyclo[4,3,1,0 3,7 ]‐8‐decen‐2‐one ( 9 ) and 44% 9‐methylene‐1,3,5‐trimethyl‐tricyclo[4,4,0,0 3,8 ]‐4‐decen‐2‐one ( 10 ), a twistane derivative. The same procedure, when applied to the sodium salt of 2,6‐dimethyl‐4‐methoxyphenol, gave in 73% yield a 26:18:54 mixture of 2,6‐dimethyl‐4‐methoxyphenyl‐(2‐methylene‐3‐butenyl)‐ether ( 11 ), 1,3‐dimethyl‐8‐methoxy‐5‐methylene‐tricyclo[4,3,1,0 3, 7 ]‐8‐decen‐2‐one ( 12 ), and 1,3‐dimethyl‐5‐methoxy‐9‐methylene‐tricyclo[4,4,0,0 3, 8 ]‐4‐decen‐2‐one ( 13 ). The tricyclic ketones 9 and 10 , or 12 and 13 , were also obtained on heating 8 or 11 respectively at 176° in decane solution. Alkylation of the sodium salt of 2,6‐dimethylphenol with 3‐butenylbromide in boiling toluene gave 1,3‐dimethyl‐tricyclo[4,3,1,0 3,7 ]‐8‐decen‐2‐one ( 17 ) as the only tricyclic product in 8% yield. The structures of the twistane derivatives 10 and 13 as well as those of the ketones 9, 12 and 17 were mainly deduced from spectroscopic data. Furthermore, the ketones 10 and 13 could be converted to the twistane derivatives 20 and 22 , possessing C 2 ‐symmetry. On the other hand, compounds 9 and 17 gave only the asymmetric derivatives 18 and 21 .