Ring-expansion of carbocyclic β-ketoesters with acetylenic esters

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Abstract
Sodium salts of 2-methoxycarbonyl-cyclopentanone, -cyclohexanone, -cycloheptanone, -cyclo-octanone and -cyclododecanone react with dimethyl acetylenedicarboxylate to yield, after neutralisation, 1-hydroxy-2,3,4-trismethoxycarbonyl-cyclohepta-, -cyclo-octa-, -cyclonona-, -cyclodeca-, and -cyclotetra-deca-1,3-diene, respectively. In a similar fashion 2-methoxycarbonylindan-1-one gave 9-hydroxy-6,7,8-trismethoxycarbonyl-5-H-benzocycloheptene while methyl 1,2,3,4-tetrahydro-1-oxonaphthalene-2-carboxylate and 6,7,8,9-tetrahydro-6-methoxycarbonylbenzocyclohepten-5-one gave respectively the corresponding eight- and nine-membered ring compounds. Methyl propiolate was shown to participate in analogous reactions with 2-methoxycarbunylcyclopentanone, methyl 1,2,3,4-tetrahydro-1-oxonaphthalene-2-carboxylate, and methyl 1,2,3,4-tetrahydro-6-methoxy-1-oxonaphthalene-2-carboxylate. In the latter case a low yield of 9,10-dihydro-2-methoxy-6,7,8-trismethoxycarbonyl-6H-benzocyclo-octen-5-one was accompanied by the isomeric Michael adduct. Some reactions of the ring-expanded products are described.

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