Use of Hine's D Values To Predict the Position of the Equilibrium in the Cope Rearrangement of Multiply Substituted 1,5-Dienes

Article abstract of DOI:10.1021/jo00128a019

A series of 1,5-dienes (1a-f) were employed to test whether Hine's D values can predict the position of equilibrium in Cope rearrangements.In the cases of the substituent pairs , ,, , and , equilibrium constants calculated with Hine's D values gave reasonable agreement with those obtained experimentally.Dienes 1g-i were prepared to test whether reduction of the ?-donating character of a nitrogen substituent (carbamoyl vs dimethylamino) would change the directing ability of the nitrogen group.The aggregate order of directing ability was N(CH3)2 > OCH3 > EtO2CN(CH3) > CH3 > H>.Diene 15a, with a more complicated substitution pattern (OCH3 and CH3 versus CH3 and H) not directly amenable to analysis with D values, can be considered to reduce to the case of .The experimental K_eq obtained agreed with that expected for the pair.Dienes 15c and 16b, designed to test the pairs and , respectively, decomposed under the gas phase conditions of the rearrangement.Attempts to effect rearrangement with Pd(II) catalysis failed.