Propanes cyclo

Ethyl cyctopropane-carboxylate. Use 22 g. of cyciopropane-carb-oxyhc acid (Section V,33) and 40 g. (24-5 ml.) of redistiUed thionyl chloride to prepare the acid chloride, b.p. 118-119° (22 g.). Treat the latter with 10-1 g. of absolute ethyl alcohol. The yield of ethyl cyclo-propane-carboxylate, b.p. 132-133°, is 13 g. 

The reaction of cyclohexene with the diazopyruvate 25 gives unexpectedly ethyl 3-cyclohexenyl malonate (26), involving Wolff rearrangement. No cyclo-propanation takes place[28]. 1,3-Dipolar cycloaddition takes place by the reaction of acrylonitrile with diazoacetate to afford the oxazole derivative 27[29]. Bis(trimethylstannyl)diazomethane (28) undergoes Pd(0)-catalyzed rearrangement to give the A -stannylcarbodiimide 29 under mild conditions[30]. 

On treatment with alkaline reagents, -toluenesulfonylhydra-zones of aldehydes and ketones yield diazo compounds which decompose in hydroxylic solvents to yield olefinic (or bicylic) compounds and in aprotic solvents to yield olefins and cyclo-propanes. ... 

Electron-deficient 1,3-dienes are known to react when heated with metho-xy(aryl)- or methoxy(alkyl)carbene complexes to afford vinylcyclopropane derivatives with high regioselectivity and diastereoselectivity [8a, 24]. Cyclo-propanation of the double bond not bearing the acceptor functional group and... 

Numerous examples have been pubhshed dealing with the heterogeneization of copper complexes, as immobihzed catalysts for the asymmetric cyclo-propanation of alkenes. Some of them have already been mentioned in the text for a direct comparison with their homogeneous coimterparts. Other reusable catalytic systems have been developed and will be described as follows. 

The above-described structures are the main representatives of the family of nitrogen ligands, which cover a wide spectrum of activity and efficiency for catalytic C - C bond formations. To a lesser extent, amines or imines, associated with copper salts, and metalloporphyrins led to good catalysts for cyclo-propanation. Interestingly, sulfinylimine ligands, with the chirality provided solely by the sulfoxide moieties, have been also used as copper-chelates for the asymmetric Diels-Alder reaction. Amide derivatives (or pyridylamides) also proved their efficiency for the Tsuji-Trost reaction. 

In another context, Soai et al. have described the enantioselective cyclo-propanation of various aldehydes using dicyclopropylzinc in the presence of a catalytic amount of a chiral thiophosphoramidate ligand derived from norephedrine and Ti(Oi-Pr)4, providing the corresponding cyclopropyl alkanols with high yields and enantioselectivities of up to 97% ee (Scheme 6.24). ... 

Scheme 8.2 Hydrogenation of dehydroamino acid with thioether-phosphine cyclo-propanated ligands.

Catalysts of the Co(salen) family incorporating chiral centers on the ligand backbone are useful in asymmetric synthesis and the field has been reviewed.1377,1378 In two examples, the hydroxy-lation reaction (Equation (14)) involving (269) proceeds with 38% ee,1379 whereas the cyclo-propanation reaction with (271) (Equation (15)) proceeds with 75% ee and with 95 5 trans cis.1380 A Co(V) salen carbenoid intermediate has been suggested in these reactions. 

Diazomalonic esters, in their behavior towards enol ethers, fit neither into the general reactivity pattern of 2-diazo-l,3-dicarbonyl compounds nor into that of alkyl diazoacetates. With the enol ethers in Scheme 17, no dihydrofurans are obtained as was the case with 2-diazo-l,3-dicarbonyl compounds. Rather, copper-induced cyclo-propanation yielding 70 occurs with ethoxymethylene cyclohexane u4). However,... 

When a second, non-activated double bond 15) is present in the allylamine, cyclo-propanation can still not compete with allylic insertion, as the example of 122 shows. 

Cu(II) EPR signal in nitriles as solvent as well as by polarographic measurements 144>. Similarly, the EPR signal disappeared when Cu(OTf)2 was used for catalytic cyclo-propanation of olefins with diazoesters 64). In these cases, no evidence for radical-chain reactions has been reported, however. The Cu(acac)2- or Cu(hfacac)2-eatalyzed decomposition of N2CHCOOEt, N2C(COOEt)2, MeCOC(N2)COOEt and N2CHCOCOOEt in the presence of cyclopropyl-substituted ethylenes did not furnish any products derived from a cyclopropylcarbinyl - butenyl rearrangement128. These results rule out the possible participation of electron-transfer processes and radical intermediates which would arise from interaction between the olefin and a radical species derived from the diazocarbonyl compound. 

In 1966, Nozaki et al. reported that the decomposition of o-diazo-esters by a copper chiral Schiff base complex in the presence of olefins gave optically active cyclopropanes (Scheme 58).220 221 Following this seminal discovery, Aratani et al. commenced an extensive study of the chiral salicylaldimine ligand and developed highly enantioselective and industrially useful cyclopropanation.222-224 Since then, various complexes have been prepared and applied to asymmetric cyclo-propanation. In this section, however, only selected examples of cyclopropanations using diazo compounds are discussed. For a more detailed discussion of asymmetric cyclopropanation and related reactions, see reviews and books.17-21,225... 

Reactions of this type are important in some gases and certainly in many gaseous mixtures. The basic proton donors are H3+, CH5+, and ions of the types C H+2n + L and C H,, + in addition to certain others. In some cases, such as in cyclo-propane, the product of the proton transfer reaction is a stable ion ... 

Examples of the use of alkylidenecyclopropanes as dienophiles are very limited in the literature. Moreover, the few examples reported deal with rather sophisticated substrates such as 2,2-difluoromethylenecyclopropane, diarylmethylene-cyclopropanaphthalenes, bicyclopropylidene and (diacylmethylene)cyclo-propanes. 

From an historical point of view, the earliest indication of spin-selective reactivity of carbenes was exhibited by the stereochemistry of the cyclo-propanation reaction. The Skell Hypothesis (Skell and Woodworth, 1956) suggests that a spin-prohibition requires the addition of a triplet carbene to an olefin to occur in at least two steps. In turn, the obligatory formation of an... 

Various approaches to epoxide also show promise for the preparation of chiral aziridines. Identification of the Cu(I) complex as the most effective catalyst for this process has raised the possibility that aziridination might share fundamental mechanistic features with olefin cyclopropanation.115 Similar to cyclo-propanation, in which the generally accepted mechanism involves a discrete Cu-carbenoid intermediate, copper-catalyzed aziridation might proceed via a discrete Cu-nitrenoid intermediate as well. 

For more examples of chiral bis(sulfonamide) catalyzed asymmetric cyclo-propanation, see Denmark, S. E. O Connor, S. P. Wilson, S. R. Angew. Chem. Int. Ed. Engl. 1998, 37, 1149, and the references cited therein. 

Structural evidence culled from the Cambridge Crystallographic Database have been incorporated where possible. The original stereochemical models have been reproduced, even those that have been improved by subsequent evidence. In many instances, a detailed description of the course of these processes is still lacking. Nowhere is this lack of information more striking than in the Cu(I) catalyzed cyclo-propanation of alkenes. 

This chapter will begin with a discussion of the role of chiral copper(I) and (II) complexes in group-transfer processes with an emphasis on alkene cyclo-propanation and aziridination. This discussion will be followed by a survey of enantioselective variants of the Kharasch-Sosnovsky reaction, an allylic oxidation process. Section II will review the extensive efforts that have been directed toward the development of enantioselective, Cu(I) catalyzed conjugate addition reactions and related processes. The discussion will finish with a survey of the recent advances that have been achieved by the use of cationic, chiral Cu(II) complexes as chiral Lewis acids for the catalysis of cycloaddition, aldol, Michael, and ene reactions. 

Further, a comparison of the effects of ligand on enantioselectivity in the cyclo-propanation and aziridination reactions revealed a linear relationship. Jacobsen argues that this reinforces the mechanistic analogy between these group-transfer reactions and suggests that the transition states are subject to similar selectivity determining factors. Finally, Jacobsen observed ligand acceleration with the diimines in this reaction. 

Thus a Cope rearrangement proceeding through a boat-like transition state is the rearrangement of cis 1, 2 divinyl cyclo-propane. 

The decomposition of these latter esters at high temperatures constitutes the important synthesis of cyclo-propane derivatives (Buchner) ... 

The synthesis of [1.1.1]propellane from 1 is essentially as reported by Michl and co-workers,10 with only a slight modification in the process of transferring the crude propellane solution. As a result of the submitters improvements in the preparation of 3-chloro-2-(chloromethy)propene4 and 1,1-dibromo-2,2-bis(chloromethyl)cyclO propane, many of the difficulties in the Szeimies route to [1.1,1]propellane have been eliminated. 

Containing the cyclo Propane Ring. J. chem. Soc. [London] 1954, 38O7. 

Since the addition of methylene to an olefin should be exothermic, with the evolution of about 90 kcal/mole, isomerisations of the initially formed cyclo-propanes are very likely, since they only need about 64 kcal/mole. RRKM-studies demonstrate that this isomerisation should be faster than the rearrangement of cyclopropanes 32, 33 to the pentenes 34, 35 Numerous studies of the photochemical generation in the gas phase provided conclusive evidence in favour of these findings uo.iii.iis). 

It is evident from Table 10 that identical mixtures of cis- and trans-cyclo-propanes obtained from either cis- or trans-olefins are quite rare. Only the cyclohexanone-carbene 59 and methyl-bisalkoxy-carbonyl-carbene 3) give... 

Experimental results [1361] and theoretical treatment [28] indicate that the cyclo-propanation of alkenes by electrophilic carbene complexes is a concerted process. Z-Olefins normally lead to the formation of the corresponding c7. -cyclopropanes, and -olefins yield fran -cyclopropanes. The relative configuration of the carbene-bound substituent and the substituents of the alkene in the final cyclopropane seems to be mainly determined by the steric bulk of these groups. In cyclopropanations of terminal alkenes with ethyl diazoacetate low diastereoselectivities are often observed [1024,1351]. These can be improved by increasing the steric demand of the substituents at the carbene or at the alkene [1033,1362]. High diastereoselectivities can, e.g., often be achieved with terf-butyl, neopentyl or 2,6-di(rerr-butyl)phenyl diazoacetate [1362] as carbene complex precursors (Figure 4.19). 

Sulfoxide (N)-(+)-(151) undergoes a highly diastereoselective asymmetric cyclo-propanation with diphenyldiazomethane and diphenylsulfonium isopropylide to form the corresponding cyclopropanes (152) (Scheme 18). A mechanistic rationale to account for the observed stereoselectivities is illustrated for Ph,CN2 (153). ... 

An attempted approach to bis(bicyclopropylidenyls) of type 87 utilizing the Kulinkovich reaction turned out to be unfruitful although the twofold cyclo-propanation of the diester 84 prepared from butadiene, worked perfectly well, and the conversion of the biscyclopropanol 85 to the dibromide 86 also gave a good yield (60%), the twofold dehydrobromination of 86 afforded only 1.7% of a mixture of meso- and d,l-S7 (Scheme 15) [56 a]. However, the direct oxidative coupling of two molecules of lithiobicyclopropylidene was accomplished under... 

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