Uber Umlagerungen bei der Cyclialkylierung von Arylpentanolen zu 2,3-Dihydro-1H-inden-Derivaten. 1. Mitteilung. Die saurekatalysierte, unter Umlagerung verlaufende Cyclialkylierung von 4-(Chlorophenyl)-2,4-dimethylpentan-2-ol

On Rearrangements by Cyclialkylations of Arylpentanols to 2,3-Dihydro-1H-indene Derivatives. Part 1. An Unexpected Rearrangement by the Acid-Catalyzed Cyclialkylation of 4-(2-Chlorophenyl)-2,4-dimethyl pentan-2-ol under Formation of trans-4-Chloro-2,3-dihydro-1,1,2,3-tetramethyl-1H-indene The acid-catalyzed cyclialkylation of 2,4-dimethyl-4-phenylpentan-2-ol led exclusively to the expected product, 2,3-dihydro-1,1,3,3-tetramethyl-1H-indene. However, analogous cyclialkylation of 4-(2-chlorophenyl)-2,4-dimethylpentan-2-ol (1) gave a ca. 1 : 1 mixture of 4-chloro-2,3-dihydro-1,1,3,3-tetramethyl-1H-indene (2) and of trans-4-chloro-2,3-dihydro-1,1,2,3-tetramethyl-1H-indene (3; Scheme 1). The specific action of the Cl substituent is investigated and a mechanism for this unexpected frame-work transposition proposed.