Cyclopropanations ester

Cyclobutane-fused pyrimidinones 39, precursors to quinone methide intermediates, have been prepared by reaction of amidines with the cyclopropane ester 38 <06EJOC2753>. 

Cyclopropane esters of sterically demanding alcohols can also be a-alkylated. Thus tert-butyl cyclopropanecarboxylate (6) reacted with LDA63 and subsequently with allyl or benzyl bromide to give the products 16A in 79% and 82% yield. 

Both compounds included here are experimental and in each case the pyridine is a benzene replacement and is not essential for the activity. The urea (103) (79SAP7802440) is a member of a highly active series that kill insects by disrupting the formation of new insect cuticle, through inhibition of chitin synthesis. The cyclopropane ester (104) (78GEP2810881) is a heterocyclic analogue of the pyrethroid insecticides, an extremely successful new class which are active on a wide range of insects. 

The methods of preparation of i. ost cyclojro-par.e acids involve first the preparation of tAie cyclic ester and subsequent hydrolysis to the free acid. That such hydrolysis did not change tne cyclic structure has been seen to be true ir. all tne cases tnus iar examined i o exceptions to tnis rule will now be studied,ior tney are botn 1,1,2,3 compounds. Aconitic ester and diazoacetic ester give by the usual reactions a cyclopropane ester as follows ... 

The cyclopropane ester was prepared by the reaction between 16 g (t)-butyl 2,5-dimethoxy-4-methylcinnamate and dimethylsulfoxonium methylide, prepared as described in the Kaiser reference in the acknowledgements. Hydrolysis of this ester gave 53% trans-2-(2,5-dimethoxy-4-methylphenyl)cyclopropanecarboxylic acid which, after recrystallization from a MeOH/... 

On the basis of triplet sensitization experiments, this rearrangement was shown to occur from the excited singlet state and to involve the biradical intermediate 111. Interestingly, vinyl cyclopropane esters 113-114 underwent geometric isomerization at a much faster rate than rearrangement on direct excitation (Scheme 8.34) [57, 58]. However, the triplet-sensitized reaction of these esters give both cyclopentene and isomerization products. 

Other terminal olefins were transformed to the corresponding cyclopropane esters with Z-menthyl and d-menthyl diazoacetates with high stereoselectivity up to 98% ee (Scheme 3). Intramolecular reaction of the phenyl-allyl ester 9 was carried out to give the bicyclic compound 10 with 86% ee and 93% yield. The enantioselectivity for intramolecular cyclopropanation of the 3-methylbutenyl ester 11 was compared with chiral Cu(I), Rh(II), and Ru Pybox catalysts Rh>Ru>Cu [26]. 

Ethylene dibromide reacts with the sodium derivative of cyanacetic ester in the same way as it does with acetacetic ester,and tne cyclopropane ester tnus obtained gives on careful hydrolysis tne cyancyclopro-... 

The first example of this transformation appeared in the literature as early as 1939/ It has been extensively studied ever since in the case of cyclopropane esters and ketones, vinyl cyclopropanes, and vinyl epoxides, a remarkable multiplicator effect of any piece of research indeed. 

The stereoselectivity of cyclopropane ester formation could also be effected by using reagents supported on linear or cross-linked polymers. The most important effects were noted with chloromethylated polymers cross-linked with divinylbenzene. The role of hyperconjugation in determining the stereochemistry of nucleophilic cyclopropanation of electrophilic alkenes has been studied and predicted In terms of equation 57 the... 

Of interest, with regard to synthetic applications are cyclopropane ester enolates and their reactions. 

An interesting and potentially useful sequence is shown in equation (107). Cyclopropane esters (305) may be prepared by the addition of diazo esters (304) to double bonds under elimination of nitrogen. After saponification the acid is 0-protonated to open the cyclopropane ring, and the resulting carbenium ion (306) is trapped by lactonization. In effect a "y-lactone has been annulated to a double bond in a re-giodefined manner.Examples are given in Scheme 10. A related reaction involves the conversion of the cyclopropane ester (307) into the lactone (308 equation 108). ... 

The Michael reaction of sulfonyl carbanions with a,p-unsaturated esters provides a useful preparation of cyclopropane esters, as shown in Scheme 47. In this sequence, the sulfonyl carbanion undergoes conjugate 1,4-addition to the a,p-unsaturated carbonyl compound followed by intramolecular elimination of the benzenesulfinate anion (Scheme 47). 

A nonpolar solvent favors conformation A, whereas conformation B is favored by more polar solvents (e.g. dimethylformamide, hexamethylphosphoric triamide) because the cation is more solvated (cf. Table 9, entries 1 and 2). However, this solvent effect is absent when BujP Cu" is used as counterion. Conformation A is more favored by relatively small counterions, such as the lithium and sodium ion, as compared to the larger potassium ion, due to the higher degree of association of the former. Steric strain between ASG and ASG is minimized in conformation B. Conformations A and B lead to trans- and c -substituted cyclopropanes, respectively. A study of cyclopropane esters, -in which the stereoselectivity of the reaction of polymer-supported reagents was compared with molecules of low-molecular weight, made clear that the steric and polar microenvironment of the polymer-supported reaction is not different enough in bulk to influence the selectivity substantially. Nevertheless, a specific influence of the solid phase can be observed at low temperatures. 

Optically active dictyopterene C enantiomers (S)- and (/ )-19 have been prepared via bio-catalytic resolution of cyclopropane esters, separation and the Cope rearrangement of pure E- or Z-isomers of l-(hex-l-enyl)-2-vinylcyclopropane (18). ... 

Reaction with enoi ethers. Wenkert and co-workers have examined the copper-catalyzed decomposition of this -diazo compound in the presence of an enol ether of an aldehyde (1) and a ketone (5). In the first case, the expected cyclopropane ester (2) was obtained. This was reduced by lithium aluminum hydride to the diol, which cyclized to the hemiaceta (3) on exposure to acid. Collins oxidation of 3 gave the spiro- 3-methylene-y-lactone 4. 

Conacher, H.B.S., and F.D. Gunstone, The Rearrangement of Methyl 12,13-Epoxyoleate by Boron Trifluoride with Formation of Cyclopropane Esters, Chem. Phys. Lipids 5 203-220 (1969). 

Gunstone, F.D., and A. 1. Said, Methyl 12-Mesyloxyoleate as a Source of Cyclopropane Esters and of Conjugated Octadecadienoates, Chem. Phys. Lipids 7 121-134 (1971). 

The normally slow formation of cyclopropane esters from alk-2--enoates by the Simmons-Smith process is somewhat quicker with... 

In continuation of a project in which a complete series of isomeric acids is synthesized in order to study their physical, chemical, and biological properties, reports have now appeared on all the cis- and fraw -octadecenoic acids, all the octadecynoic acids, on many octadecadiynoic and octadec-adienoic acids, and on cyclopropane esters made from the mono- and di-enoates. Details of the chromatographic and spectroscopic behaviour of these isomeric esters are included. The cis- and rm j-octadecenoic acids show an alternation in the melting points when related to the position of unsaturation this is not apparent among isomeric octadecynoic acids. 

Two research groups report the formation of appreciable quantities of cyclopropane compounds by reaction of appropriate derivatives of methyl ricinoleate, which contains a homoallylic system. One group employed the crystallized tosyl ester of the /ru/ij -isomer, the other used methyl 12-mesyloxy-oleate. Hydroxy-, methoxy-, acetoxy-, and chloro-cyclopropane esters (30) were formed (30—60% yield) under controlled pH conditions in acidic media the more stable homoallylic system is regenerated. 

Michael addition reactions of allyl sulphones and a/3-unsaturated carbonyl compounds provide useful starting points in synthesis, illustrated in a synthesis of chrysanthemate ester [Me2C=CHCH2S02ph -I- Me2C=CHC02R -> MeaC= CHCH(S02Ph)CMe2CH2C02R cis- and tm/is-cyclopropane esters]. ... 

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