Diazoacetophenones, hydrolysis

Dependence of the rate of hydrolysis on the first power of [H30 +] at a constant ionic strength has been established for diazoacetone [206], diazoacetophenone [207], and a few other compounds [207]. For 4 primary diazoketones [206] and 4 primary diazosulfones [208, 209], hydrolysis rates have been measured in moderately concentrated perchloric acid in water or in dioxane—water. In all examples, slopes of plots of log ft versus H0 are between —0.95 and —1.17. 

It is interesting to compare reactivities of various diazo compounds (Tables 17 and 18). The substrates with the highest hydrolysis rate coefficients are diazoacetate ion and ethyl diazoacetate. The rate coefficients, kH, of diazoacetone and diazoacetophenone are 1.5 powers of ten lower and those of the diazosulfones are 2 to 3.5 powers of ten lower than the value for ethyl diazoacetate. Substituent effects on the hydrolysis rates of diazoacetophenone [212, 213] and phenylsulfonyl-diazomethane [208] follow Hammett s rule with p values of ca. —1 (Table 20) which is a little less negative than expected for substituent effects on the protonation equilibria. 

Preparation by hydrolysis of o-acetoxy-a-acetoxy-acetophenone (SM) with aqueous potassium hydroxide solution by gently wanning for 10-15 min on a water bath maintained at 80° (71%). SM was obtained by cupric chloride-catalyzed decomposition of o-acetoxy-a-diazoacetophenone in dioxane solution in the presence of acetic acid (65%, m.p. 161-162°) [5137]. 

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