Cyclopropane derivatives acidity

In other cases, sulfenic acid elimination can involve y-hydrogen atoms with the formation of cyclopropane derivatives. y-Klimination is favored when DMSO is the reaction solvent. An example involving l-methylsulfinyl-2-ethyl-3-phenyl propane [14198-15-3] is shown in equation 13 (45) ... 

Furan and thiophene undergo addition reactions with carbenes. Thus cyclopropane derivatives are obtained from these heterocycles on copper(I) bromide-catalyzed reaction with diazomethane and light-promoted reaction with diazoacetic acid ester (Scheme 41). The copper-catalyzed reaction of pyrrole with diazoacetic acid ester, however, gives a 2-substituted product (Scheme 42). 

High vacuum pyrolysis, heating in organic bases, contact with acidic adsorbents and reaction at room temperature with perchloric acid or boron trifluoride etherate cleaves the pyrazoline to give a 45-60% yield of the cyclopropane derivative (13) as well as 9 % of the unsaturated methyl compound (14). ° ... 

Similar results are observed in the conjugative addition of CH-acidic methylene compounds with the metal derivatives of 2-nitro-5,10,15.20-tetraphenylporphyrin (6). The nickel porphyrin 6 (M = Ni) yields with an excess of dimethyl malonate the cyclopropane derivative 7 whereas the copper porphyrin 6 (M — Cu) forms with two equivalents of malononitrile the bisadduct 8.111... 

Esters of a-diazoalkylphosphonic acids (95) show considerable thermal stability but react with acids, dienophiles, and triphenylphosphine to give the expected products. With olefinic compounds in the presence of copper they give cyclopropane derivatives (96), but with no such compounds present vinylphosphonic esters are formed by 1,2-hydrogen shift, or, when this route is not available, products such as (97) or (98) are formed, resulting from insertion of a carbenoid intermediate into C—C or C—H bonds. The related phosphonyl (and phosphoryl) azides (99) add to electron-rich alkynes to give 1,2,3-triazoles, from which the phosphoryl group is readily removed by hydrolysis. 

A similar, although less marked difference characterizes the cyclopropanation of olefins 41 and 42. In the presence of either copper or copper complexes whose chelating ligands contain an azomethine moiety derived from an a-amino acid, no stereoselectivity was observed with diene 41, whereas the cyclopropanes derived from 42 occur with cisjtrans ratios of 57 43 to 69 31, depending on the catalyst93). 

The chemistry of a-haloketones, a-haloaldehydes and a-haloimines Nitrones, nitronates and nitroxides Crown ethers and analogs Cyclopropane derived reactive intermediates Synthesis of carboxylic acids, esters and their derivatives The silicon-heteroatom bond Syntheses of lactones and lactams The syntheses of sulphones, sulphoxides and cyclic sulphides... 

Treatment of isoxazoline-fiised [60]fullerene 48 with NaOMe in the presence of MeOH gave the p-hydroxy nitrile derivative 49 in good yield <00SL361>. The synthesis of the enantiomerically pure cyclopropane amino acid 51 covalently attached to a fulleroisoxazoline has been achieved . 

CYCLOPROPANECARBOXYLIC ACID, cis-2-PHENYL-, 50, 94 Cyclopropane derivatives, synthesis, 52, 22, 33, 132 Cyclopropenes, 50, 30 Cyclopropenone, di-tert-buty1-,... 

Cyclopropane is the only planar cis alicyclic compound and the three points lie in the single plane. Its monosubstituted derivative also has a plane of symmetry and the substituted carbon atom is not asymmetric. Let us take the case of cyclopropane-monocarboxylic acid. It has a plane of symmetry shown by the dotted line and hence the molecule is inactive ( xx). 

HCCl2C00Me could be used instead of CHCI3 with similar results [128]. For (43a), cyclization by intramolecular Sn2 reaction competes with protonation, and when stoichiometric amounts of EGB and CHCI3 were used, the cyclopropane derivative was the main product. Scheme 32, since protonation of the intermediate anion now has to be from (33H), which is less acidic than CHCI3 [128],... 

A second example of the use of ionic chiral auxiliaries for asymmetric synthesis is found in the work of Chong et al. on the cis.trans photoisomerization of certain cyclopropane derivatives [33]. Based on the report by Zimmerman and Flechtner [34] that achiral tmns,trans-2,3-diphenyl-l-benzoylcyclopropane (35a, Scheme 7) undergoes very efficient (0=0.94) photoisomerization in solution to afford the racemic cis,trans isomer 36a, the correspondingp-carboxylic acid 35b was synthesized and treated with a variety of optically pure amines to give salts of general structure 35c (CA=chiral auxiliary). Irradiation of crystals of these salts followed by diazomethane workup yielded methyl ester 36d, which was analyzed by chiral HPLC for enantiomeric excess. The results are summarized in Table 3. 

The second example described here is dormant seeds from Rosa canina. Extracts of these seeds also inhibit germination of seeds of several plants (10). In Figure 5 a scheme is given for extraction and separation oF"three different inhibitor compounds. All these are present in the acid fraction. The first essential step is chromatography on Sephadex LH-20, which separates inhibitor I from inhibitor II and III. Inhibitor I was identified as abscisic acid. The other two inhibitors were separated by methylation with diazomethane, fractional distillation, and column chromatography. The second inhibitor is the a-pyrone 1 . Reaction with diazomethane transforms it into the bi-cyclic compound 19. This bicyclic compound is even more active than the parent a-pyrone 1 . Since we sought structural requirements for bioactivity here also,we tested several synthetic a-pyrones ( 0 - 22) for bioactivity. These compounds had no inhibitory activity. We alio tested the cyclopropane derivatives 23 and 24 In Table II, the bioactivity of the bicyclic compound T9 and two such derivatives is compared. The presence of several carboxylic acid groups seems to be essential (or at least helpful) for bioactivity in this case also. 

Since (Z)- and ( )-stereoisomers of unsaturated oxazolones can be obtained using appropriate isomerization procedures, cis and trans isomers of cyclopropane derivatives can be obtained in a stereoselective manner, although special care must be taken with experimental conditions to obtain the best stereoselectivity. Both racemic cis- and fraui-l-amino-2-phenylcyclopropanecarboxylic acid 641 and 644 have been obtained from the corresponding (Z)- or ( )-4-benzylidene-2-phenyl-5(4//)-oxazolone 621 and 642 using diazomethane. Care was taken to affect the... 

Byproducts of this rearrangement are cyclobutenes, cyclopropane derivatives and allenic alcohols. The ratio of these products depends on the substitution of the substrate and on the reaction conditions. For example, 3-methyl-5-tosyloxypenta-l,2-diene (3) gives 75% of 1-methyl-2-methylenecyclobutanol (4) upon hydrolysis with water and calcium carbonate at 100 °C, while acetolysis with acetic acid/sodium acetate at 80 °C, and subsequent treatment with lithium aluminum hydride, provides only 37% of the cyclobutanol.12... 

Although the ring is not as easily opened in tais acid as it is in many of the other cyclopropane derivatives,it is by no Mans entirely unreactive. 

Another type of chiral Michael acceptor, the oxazepine derivatives (47), is prepared by condensation of the (-)-ephedrine-derived malonic acid derivative (46) with aldehydes (Scheme 18).51 52 Treatment of (47) with a variety of Grignard reagents in the presence of NiCh affords, after hydrolysis and decarboxylation, the 3-substituted carboxylic acids (48), in most cases with more than 90% ee. Diastereoselective Michael additions to (47) were also used for the preparation of optically active cyclopropane derivatives (49)53 and P-substituted-y-butyrolactones (50 Scheme 18).54 A total synthesis of indolmycin is based on this methodology.55... 

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