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Über Umlagerungen bei der Cyclialkylierung von Arylpentanolen zu 2,3‐Dihydro‐1 H ‐inden‐Derivaten, 2. Mitteilung
Author(s) -
Giovannini Edgardo,
Hengartner Urs,
Pasquier Pierre
Publication year - 2002
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 - 10.1002/1522-2675(200206)85:6<1841::aid-hlca1841>3.0.co;2-e
Subject(s) - chemistry , indene , stereochemistry , medicinal chemistry
On Rearrangements by Cyclialkylations of Arylpentanols to 2,3‐Dihydro‐1 H ‐indene Derivatives. Part 2. An Unexpected Rearrangement by the Acid‐Catalyzed Cyclialkylation of 2,4‐Dimethyl‐2‐phenylpentan‐3‐ol under Formation of trans ‐2,3‐Dihydro‐1,1,2,3‐tetramethyl‐1 H ‐indene The acid catalyzed‐cyclialkylation of 4‐(2‐chloro‐phenyl)‐2,4‐dimethylpentan‐2‐ol ( 1 ) gave two products: 4‐chloro‐2,3‐dihydro‐1,1,3,3‐tetramethyl‐1 H ‐indene ( 2 ) and also trans ‐4‐chloro‐2,3‐dihydro‐1,1,2,3‐tetramethyl‐1 H ‐indene ( 3 ). A mechanism was proposed in Part 1 ( cf. Scheme 1 ) for this unexpected rearrangement. This mechanism would mainly be supported by the result of the cyclialkylation of 2,4‐dimethyl‐2‐phenylpentan‐3‐ol ( 4 ), which, with respect to the similarity of ion II in Scheme 1 and ion V in Scheme 2 , should give only product 5 . This was indeed the experimental result of this cyclialkylation. But the result of the cyclialkylation of 1,1,1,2′,2′,2′‐hexadeuterated isomer [ 2 H 6 ]‐ 4 of 4 ( cf. Scheme 3 ) requires a different mechanism as for the cyclialkylation of 1 . Such a mechanism is proposed in Schemes 5 and 6. It gives a satisfactory explanation of the experimental results and is supported by the result of the cyclialkylation of 2,4‐dimethyl‐3‐phenylpentan‐3‐ol ( 9 ; Scheme 7 ). The alternative migration of a Ph or of an i‐Pr group ( cf. Scheme 6 ) is under further investigation.