Methyl compounds, from cyclopropanes

It is thus anticipated that compressive stress inhibits while tensile stress promotes chemical processes which necessitate a rehybridization of the carbon atom from the sp3 to the sp2 state, regardless of the reaction mechanism. This tendency has been verified for model ring-compounds during the hydrogen abstraction reactions by ozone and methyl radicals the abstraction rate increases from cyclopropane (c3) to cyclononane (c9), then decreases afterwards in the order anticipated from Es [79]. The following relationship was derived for this type of reactions ... 

Early IR and UV-VIS spectroscopic studies on the formation of carbonium ions from triphenyl methyl compounds on zeolites, titania and alumina were carried out by Karge [111]. In 1979, upon interaction of olefins Hke ethene and propene with zeoHtes CoNaY, NiCaNaY, PdNaY and HY, the appearance of electronic bands between 230 and 700 nm was observed by Garbowski and PraHaud and attributed to an allylic carbenium ion which upon thermal treatment transforms into polyenyl carbenium ions and/or aromatic compounds [112]. These findings were corroborated and extended by studies of the interaction of propene, cyclopropane and frans-butene on zeoHtes NaCoY and HM [30]. In spite of the obscuration of the spectrum in the range between 450 and 700 nm by the threefold spHt d-d band of tetrahedraUy coordinated Co(II) ions in the case of zeoHte NaCoY,the development of bands near 330,385 and 415 nm was assigned to unsaturated carbocations. 

The bark of Croton eluteria (Euphorbiaceae) yields, on steam distillation, cascarilla essential oil which is used as a tonic. The main component of the acid fraction of this oil is cascarillic acid ([aJo -10.5°, methyl ester), a cyclopropane carboxylic acid (123) (79). The stereochemistry of the cyclopropane ring was established as trans by comparing H-NMR spectra and retention times on gas chromatograms of methyl esters of the synthetic trans- and cw-isomers with those of the natural compound (147). It is interesting that compounds with closely related structures have been found in an algae and in an insect. Dictyopterene A (124) was isolated from the essential oil of algae of the genus Dictyopteris (77) and (Z)-3-decenoic acid from carpet beetle, Anthrenus flavipes, as a sex pheromone (41). 

An advantage of this method of obtaining cyclopropanes from trihalo-methyl compounds is that basic conditions are not needed. 

As it is known from experience that the metal carbenes operating in most catalyzed reactions of diazo compounds are electrophilic species, it comes as no surprise that only a few examples of efficient catalyzed cyclopropanation of electron-poor alkeiies exist. One of those examples is the copper-catalyzed cyclopropanation of methyl vinyl ketone with ethyl diazoacetate 140), contrasting with the 2-pyrazoline formation in the purely thermal reaction (for failures to obtain cyclopropanes by copper-catalyzed decomposition of diazoesters, see Table VIII in Ref. 6). 

From a variety of differently substituted compounds, best results were obtained with the catalysts 195a-c in combination with /-methyl diazoacetate and monoolefins, cyclopropanes were obtained with a relatively high trans/cis ratio and enantiomeric excesses of 44-89% (Table 12). The absolute configuration at the catalyst s chiral center determines the enantioselectivity for both diastereoisomers. 

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. 

Neither CS2 nor TMS are ideal standards. The 13C signals of CS2 and carbonyl carbons overlap, as do the 13C signals of cyclopropane and some methyl carbons with TMS (Fig. 3.3). Furthermore, the 13C resonance of TMS has been shown to suffer from solvent shifts of the order of + 0.1 to 1.5 ppm in common NMR solvents, even at infinite dilution [74]. This must be considered if 13C shifts relative to TMS of one compound in different solvents are to be compared. There are two alternative methods to overcome this problem one is to use cyclohexane as the internal reference cyclohexane was shown to have 13C solvent shifts lower than + 0.5 ppm [74], The other alternative is to use TMS as an external reference (Sections 1.9.3 and 2.8.5) and to make bulk susceptibility shift corrections according to eq. (1.44). 

The total synthesis of ( + )-Erysotramidine (2) has been described by Ito et al. (137) starting from the amide (174) (Scheme 39). After O-mesylation to 177, base-catalyzed reaction gave the cyclopropane derivative (178) which with zinc in acetic acid was reduced to 179, which was identical to the product (135) of O-methylation of 172. Conversion of 178 to the thioketal (180) was followed by reaction with phenylselenyl chloride. A mixture of two compounds, 181 and 182, was produced the former could be transformed quantitatively to the latter. Finally, treatment of 182 with silver nitrate in methanol gave 183, which was then desulfurized to yield erysotramidine (2). 

According to Scheme 1 methyl 2-siloxycyclopropanecarboxylates should also be available from donor-acceptor-substituted olefins like 100, which are easily synthesized by silylation of the corresponding 1,3-dicarbonyl compounds. Cyclopropanation of 100 with methyl diazoacetate or diazomethane could be realized in the presence of Cu(II)-catalysts, but due to the relatively low reactivity of the olefins a large excess of diazoalkanes had to be employed. This makes the isolation of 101 troublesome and therefore direct hydrolysis with acid to give 1,4-dicarbonyl compounds 102 is advantageous (Eq. 32) 66). 

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