Synthesis of 1,5-Disubstituted Tricyclo2,5>pentanes. The Crystal and Molecular Structures of 1,5-Bis(acetoxymethyl)tricyclo2,5>pentan-3-one

Article abstract of DOI:10.1021/jo00143a012

A series of substituted cyclopropene esters has been synthesized by the dirhodium(II) tetraacetate catalyzed addition of ethyl and tert-butyl diazoacetate to 1,4-diacetoxy-2-butyne.Selective hydrolysis converted ethyl 1,2-bis(acetoxymethyl)cyclopropene-3-carboxylate (II) to ethyl 1,2-bis(hydroxymethyl)cyclopropene-3-carboxylate (III) and then to 1,2-bis(hydroxymethyl)cyclopropene-3-carboxylic acid (IV).Acetic anhydride treatment of IV yielded 1,2-bis(acetoxymethyl)cyclopropene-3-carboxylic acid (V).However, the latter was more readily prepared by trifluoroacetic acid promoted deesterification of tert-butyl 1,2-bis(acetoxymethyl)cyclopropene-3-carboxylate (VI).The rhodium carboxylate catalyzed reaction leading to VI also yielded a small amount of exo,exo-di-tert-butyl 1,3-bis(acetoxymethyl)bicyclo<1.1.0>butane-2,4-dicarboxylate (VII) as a side product.The carboxylic acid V was converted to the acid bromide, 1,2-bis(acetoxymethyl)cyclopropene-3-carbonyl bromide (VIII), which upon treatment with diazomethane at -78 deg C yielded 1,2-bis(acetoxymethyl)-3-(diazoacetyl)cyclopropene (IX).The latter reaction yields 1,2-bis(acetoxymethyl)-3-(bromoacetyl)cyclopropene (X) when worked up with acetic acid before completion of the reaction.A side product pyrazoline diazo ketone, XI, was formed by the addition of diazomethane across the double bond of IX.Treatment of IX with Rh2(OAc)4 yielded 1,5-bis(acetoxymethyl)tricyclo<2.1.0.0^2,5>pentan-3-one (XII).The keto diacetate XII is readily hydrolyzed to 1,5-bis(hydroxymethyl)tricyclo<2.1.0.0^2,5>pentan-3-one (XIII) or converted to the ketals: 1,5-bis(acetoxymethyl)-3,3-diethoxytricyclo<2.1.0.0^2,5>pentane (XVa) and 1',5'-bis(acetoxymethyl)spiro<1,3-dioxolalane-2,3'-tricyclo<2.1.0.0^2,5>pentane> (XVb).The latter are readily hydrolyzed to the corresponding diols: 1,5-bis(hydroxymethyl)-3,3-diethoxytricyclo<2.1.0.0^2,5>pentane (XVIa) and 1',5'-bis(hydroxymethyl)spiro<1,3-dioxolane-2,3'-tricyclo<2.1.0.0^2,5>pentane> (XVIb).An X-ray crystal structure of the tricyclic keto diacetate XII reveals an extremely short (1.416 Angstroem) bridging carbon-carbon single bond.