摘要：

The rearrangement of 2,3-dimethyl-2,3-pentanediol (IIb) in aqueous sulfuric acid yielded 83% methyl t-amyl ketone and 17% ethyl t-butyl ketone. Isotopic labeling showed that the methyl ketone arose both by ethyl migration (69%) and methyl migration (31%). Similar rearrangement of 2,3,4,4-tetramethyl-2,3-pentanediol (IIc) led to 98.6% methyl triptyl ketone and 1.4% hexamethylacetone. In this case the methyl ketone was shown to result entirely from t-butyl migration. The relative rates of rearrangement of pinacol (IIa), IIb and IIc were 1.0:7.2 : > 103. The tendencies of alkyl groups to migrate in this rearrangement are expressed in terms of partial rates, which are in the ratio >4000: 17 : 1 for t-butyl, ethyl and methyl, respectively. A reaction mechanism is discussed in the light of these and other recent results.

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