Isopropenyl acetoacetate synthesis

The rDA route to isopropenyl acetoacetate and to vinyl acetoacetate was apparently the first synthesis of acetoacetate esters of enols. The reaction between diketene (26) and norbomenols (25a) and (25b) generated the protected ethylene cycloadducts (27), which upon FVP gave the desired isopropenyl acetoacetate (28a) in 48% yield and vinyl acetoacetate (28b) in 61% yield (equation 20). ... 

Industrial synthesis of nerolidol starts with linalool, which is converted into ger-anylacetone by using diketene, ethyl acetoacetate, or isopropenyl methyl ether, analogous to the synthesis of 6-methyl-5-hepten-2-one from 2-methyl-3-buten-2-ol. Addition of acetylene and partial hydrogenation of the resultant dehydroner-olidol produces a mixture of cis- and trans-nerolidol racemates. 

Linalool can be converted to geranyl acetone by the Carroll reaction (156). After transesterification with ethyl acetoacetate, the intermediate ester thermally rearranges with loss of carbon dioxide. Linalool can also be converted to geranyl acetone by reaction with methyl isopropenyl ether. The linalyl isopropenyl ether rearranges to give geranyl acetone. Geranyl acetone is an important intermediate in the synthesis of isophytol [505-32-8], famesol [106-28-5], and nerolidol [40716-66-3]. Isophytol is used in the manufacture of Vitamin E and thus linalool is a key intermediate in the synthesis of the latter. All of these reactions are shown in Fig. 8.55 in the section on nerolidol. 

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