Dimethyl citraconate

Another route involving 1,3-dipoIar addition was next attempted (54). The key feature of this route is a cycloaddition of nitrile oxide (55) 88 with citraconate 87 (Scheme 16). Treatment of 89 prepared from 3-bromopropanol with phenyl isocyanate produced the nitrile oxide 88 which was then subjected to cycloaddition with dimethyl citraconate 87 to afford the adducts 86a and 86b as a 1 1 mixture. In this reaction, as expected, 86a, in which the less hindered oxygen is substituted at the quaternary carbon, was the major product (56). Conveniently, however, the undesired adduct 86b could be separated in the following dehydration step. These adducts were next subjected to various reduction conditions (57) in order to obtain intermediate 85 (eq.9). Unfortunately, we could not obtain any of the desired compound even under Curran s conditions (Raney-Ni (W-2), boric acid) which are mild enough to suppress undesired side reactions. All compounds produced in this reduction were retro-aldol products 90-93 probably derived from 85 or its imine form. This... 

Substrates for hydrogenation were methyl cinnamate (I), methyl-a-methyl cinnamate (II), methyl-p-methyl cinnamate (III), methyl-a-phenyl cinnamate (IV), dimethyl itaconate (V), dimethyl mesaconate (VI), and dimethyl citraconate (VII). Their structures and the names of the corresponding hydrogenation products are given in Table 1. 

Dimethyl maleate heated 1 hr. with triphenylphosphine at 150° dimethyl fumarate. Y ca. 100%.—Dimethyl citraconate is not isomerized under these conditions. A. R. Hands, Soc. 1964, 1181. 

Dimethyl-2-butenoic acid Dimethylcarbamoyl chloride Dimethyl chlorothiophosphate Dimethyl citraconate... 

Dihydro-l,3-dimethyl-l/f-purine- 1,2-Diiodobenzene 3760 Dimethyl citraconate 4129... 

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