Abstract
Synthesis of 5, 6-dimethy1-5-hepten-2-one 8 from 3-methylene-2, 6-heptanedione is described.3-Methylene-6, 6-ethylenedioxy-2-heptanone [2 a] was obtained as a major product by the reaction of with ethylene glycol. The reaction of with propylene glycol, ethylene oxide or propylene oxide as a acetalizing reagent gave the corresponding monoacetals [2] (Table 1). The structure of by-products obtained by these reactions was characterized. Hydrogenation of [2 a] gave 3-methyl-6, 6-ethylenedioxy-2-heptanone [4]. The reaction of [4] with methylmagnesium chloride in THF gave 2, 3-dimethyl-6, 6-ethylenedioxy-2-heptanol [7], and acid decomposition of the product gave [8], a key intermediate for the preparation of a-irone.
