Cyclopropanes ring opening with carboxylic acids

Ring Opening of Cyclopropanes with Carboxylic Acids... 

MO calculations have been carried out on the isomerization of cyclopropane to propene, and the MNDO method has been used to study the reaction pathway and to optimize the structure of reactant, transition structure, and product of the ring opening reaction of bicyclo[1.1.0]butane. Various methods have been employed to estimate the rate constants for ring opening of the 2-cyclopropyl-2-propyl radical. 1-Acceptor-1-sulfenyl-substituted 2-vinylcyclopropanes of the type (430) have been found to afford 6-sulfenyl-a,jS y, -unsaturated carboxylic esters and nitriles (431) upon treatment with acid, by a process which involves C(l)—C(2) bond fission and a novel 1,5-sulfenyl rearrangement (see Scheme 110). It has been shown that the benzophenone-sensitized photolysis of vinyl norcaradiene derivatives, such as 5-(2-methylprop-l-enyl)-3-oxatricyclo[4.4.0.0 ]deca-7,9-dien-4-ones (432), results in the regioselective cleavage of only one of the cyclopropyl c-bonds to afford isochroman-3-one derivatives (433). It has been reported that the major product obtained from the reaction of structurally diverse a-diazo ketones with an electron-rich alkene in the... 

In this section we analyze information about metabolic cleavage or breakdown of cyclopropane rings in three instances the biosynthesis of irregular monoterpenes, the ringopening of cycloartenol (20) derivatives, and the metabolic opening of 1-aminocyclopropane-1-carboxylic acid (ACPC) (9) by two quite distinct fragmentation routes. We will not explicitly discuss the processing of presqualene pyrophosphate (77) and prephytoene pyrophosphate (89) to squalene (76) and phytoene (88) respectively, since those transformations have already been dealt with in Section II. 

The majority of the bicyclic cyclopropanes so obtained undergo facile acid-catalyzed ring open-ing/isomerization to the corresponding (Z,Z)-6-oxohexa-2,4-dienoates this transformation already occurs when the workup by column chromatography is performed on silica gel rather than on alumina. Treatment of the bicyclic systems (as well as the E,Z- and Z,Z-dienes) with iodine in dichloromethane results in isomerization to (is,is)-l,4-diacylbuta-l,3-dienes in high yield.The ring-opened products in carbenoid reactions of furans are not likely to result from isomerization of the alkyl-2-oxabicyclo[3.1.0]hex-3-ene-e c/o-6-carboxylates. For mechanistic proposals, see refs 300 and 301. 

A lactone can be refunctionalized to an amino acid as well as a carboxylic acid. Reaction of 7.34 with potassium phthalimide opened the lactone ring to give a phthalimido-acid. Removal of the phthalimide group gave 2-methylamino-l-phenyl-cyclopropane-1-carboxylic acid, 7.35Amino acid 7.35 was tested as a potential antidepressant, and several aryl analogs were prepared the 4-chlorophenyl, the 4-methylphenyl, and the 4-methoxyphenyl derivatives. 

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