?-Complexed β-Arylalkyl Derivatives. 6. Effect of Electron-Withdrawing Substituents on the Acetolysis of 2--2-methyl-propyl Methanesulfonates

Article abstract of DOI:10.1021/jo01296a003

The ?-(arene)chromium tricarbonyl complexes of m-methoxy- and p-chloro-substituted 2--2-methyl-1-propyl (neophyl) methanesulfonates have been prepared and their acetolysis rates determined.At 99.5 deg C, the complexes are, respectively, 1.1 and 1.6 times as reactive as their noncomplexed counterparts.The p-chloroneophyl complex yields, after oxidative decomplexation of the product mixture with Ce(IV), 54percent 3-(p-chlorophenyl)-2-methyl-2-propyl acetate, 34percent 3-(p-chlorophenyl)-2-methyl-1-propene, and 12percent 1-(p-chlorophenyl)-2-methyl-1-propene.No nonaryl-migrated products are observed.The acetolysis rates of p-methoxy-, m-methoxy-, p-methyl-, m-methyl-, and p-chloroneophyl complexed and noncomplexed methanesulfonates at 99.5 deg C are well correlated by the Yukawa-Tsuno relations: and .The meaning of these correlations is discussed, and it is concluded that in addition to its strong inductive electron withrawal, ?-tricarbonylchromium acts amphoterically to donate or withdraw electrons by resonance.From a comparision of the relative acetolysis rates of the p- and m-methoxy complexes, it is suggested that the ?-tricarbonylchromium probably does not act via direct d-orbital participation to accelerate the solvolysis rates of the complexes.