Cyclopropyl carboxylic esters

Acyl azoliums generated from enals have been converted to cyclopropyl carboxylic esters with ee < 99% by reaction with sulfur ylides. Some FLPs have been found to i react by conjugate P/B addition to unsaturated ketones and esters, whereas 1,2-addition to corresponding aldehydes is usual. ... 

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... 

However, when they oxidized tetraethylammonium cyclopropyl carboxylate (46) no Kolb6 dimer was formed but an allylic ester was formed instead. In contrast to this result,... 

Chiral 2,2-disubstituted cyclobutanones have been obtained by asymmetric rearrangement of chiral sulfinyl- 177,178 and sulfanylcyclopropanes.179 Using readily available cyclopropyl 4-tolyl (/ )-sulfoxide (l),180 the requisite sulfinylcyclopropanes 3 and 3 were obtained by a sequence of lithiation, reaction with carboxylic acid esters and stereoselective addition of Grignard reagents to the ketones 2 thus formed.178 The corresponding sulfanylcyclopropanes 4 and 4 resulted from a sequence of protection, reduction and deprotection.179... 

The ethyl ester of l-cyclopropyl-7-(2,6-dimethyl-4-pyridyl)-5,6,8-trifluoro-4-oxo-1,4-di-hydroquinoline-3-carboxylic acid26 and of the closely related (7>)-10-(2,6-dimethyl-4-pyridyl)-8,9-difluoro-3-methyl-7-oxo-2.3-dihydro-7//-pyrido[1,2,3-tfe]-l,4-bcnzoxazine-6-carboxylic acid 427 can be thiolated in tetrahydrofuran at low temperature, using the strong base sodium hydride. 

Dichloro-3-ethoxycarbonylacetyl-5-fluoropyridine (52) with triethyl orthoformate and subsequently cyclopropylamine gave 7-chloro-l-cyclopropyl-6-fluoro-4-oxo-l,4-dihydro-l,8-naphthyridine-3-carboxylic acid (53) ( 60% note hydrolysis of the ester group).487... 

Ethyl l-cyclopropyl-4-oxo-7-phenylsulfonyl-6-trifluoromethyl-l,4-dihydro-l,8-naphthyridine-3-carboxylate (7) gave the crude ester (8, R = Et) (piperazine, MeCN, 20°C), characterized after saponification to l-cyclopropyl-4-oxo-7-(piperazin-l-yl)-6-trifluoromethyl-l,4-dihydro-1,8-naphthyri dine-3-car-boxylic acid (8, R = H) (NaOH, EtOH 37% overall).1167... 

A new carboxy protecting group that takes advantage of the facile solvolysis of cyclopropyl methyl substrates was proposed by Carpino et al.f The dicyclopropylmethyl (Dicyc-propme) ester can be used for carboxylic acid protection where selective removal is required in the presence of tBu or Trt side-chain protection. The ester is stable toward conditions of... 

R and R may be H, methyl, cyclopropyl, cyano, or ester groups. The phenylcarbene formed on irradiation of trans-l,2-diphenyloxirane has been trapped and identified in the form of a cyclopropane derivative in methanol in the presence of benzyl methyl ether and alkenes. Photolysis in the presence of 2,3-dimethyl-2-butene proceeds by cycloaddition with the formation of cyclopropane-carboxylic acid and oxetane derivatives (Eq. 368). ... 

More investigations have been performed with cyclopropyl ketones. The isomerization of the cis-cyclopropyl ketone 209 to its trans isomer 210 was only achieved by means of the rather basic dimsyl sodium in dimethyl sulfoxide at 60°C . Similarly, esters of cyclopropane carboxylic acids have been isomerized ... 

The low tendency of cyclopropyl esters to form the ester enolate is also documented by the following examples Boche and Martens have reported that methyl cis-bicyclo[6.1.0]nona-2,4,6-triene-flnti-9-carboxylate (227) loses a proton at C(l) when treated with LDA to give, probably via the cyclopropyl anion 228", the allyl anion 229". Russell and coworkers have shown that ethyl 2-methyl-2-nitrocyclopropanecarboxylate (230) gives the 2-methylenecyclopropanecarboxylate (231) when treated with sodium hydride. 

During the total synthesis of (+)-anthoplalone by K. Fukumoto et al. one of the intermediates was a cyclopropyl methyl ketone, and the synthetic sequence required the conversion of this functionality to the corresponding cyclopropane carboxylic acid methyl ester. This transformation was accomplished via the haloform reaction using bleach in methanol. The methyl ester and some carboxylic acid was obtained after this step, so the product mixture was treated with diazomethane to convert the acid side product to the methyl ester. 

Reductive carbonylation of 1,1-dibromocyclopropanes with tetracarbonylnickel in dimethyl-formamide in the presence of a nucleophile is a powerful method for direct introduction of carboxylic acid functions to cyclopropanes. Nucleophiles, such as alcohols, amines, and silylamines, are particularly reactive and give cyclopropyl esters and amides, respectively, in reasonable to good yields, e.g. formation of 5 and... 

A cyclopropyl to allyl radical rearrangement could also be induced in 20 % yield by the thermal decomposition (in carbon tetrachloride at 32 °C with sonication) of the A-hy-droxypyridine-2-thione ester of l-fluoro-2,2-diphenylcyclopropane-l-carboxylic acid (Barton decarboxylation reaction). ... 

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