2- cyclopropyl sulfides

The cyclopropanation reactions were extended to the formation of cyclopropyl sulfides 349-353 in good yields425. 

A companion reagent to the ylide is the corresponding metalated sulfide 30 which arises by the lithiation of 29 with n-butyllithium 66). The latter forms by base closure of 28. Since closure of 28 b involves use of n-butyllithium, the cyclopropyl sulfide 29 simply becomes an intermediate which is metalated in situ to give 30 directly67). A non-metalation sequence involves 32 which undergoes reductive... 

Because cation stabilization makes an important contribution, N-, S-, and O-substituents are often used to support C-C bond cleavage [109, 144]. C-C bond scission is readily achieved in strained carbocyclic [145] or heterocyclic [146] ring systems, with many examples stemming from cyclopropyl sulfides [147]. 

Sulfur and selenium substituents can serve both as the activating group and as the leaving group. Thus, thio- and selenoacetals of aldehydes bearing a leaving group on the jS-carbon atom readily afford cyclopropanone thio- and selenoacetals, respectively. 1,3-Bis (phenylthio) propanes as well as 3-halopropyl sulfides " provide cyclopropyl sulfides... 

Allylation of a-thio-35), a-seleno-35) and a-silyl- 35,77) cyclopropyllithiums was not very successful35) but addition at —78 °C of 0.5 equivalent of copper (I) iodide-dimethylsulfide complex 35,106, W7> prior to the allylhalide leads 35,106,107) to a very high yield of homoallyl cyclopropyl sulfides or selenides (Scheme 24). Similar observations have been made on cyclobutyl derivatives3S). It is not clear at present whether a cuprate is involved in the process but we have evidence ( Se-NMR) that a new species is transiently being formed, at least in the seleno series. The synthesis of homoallyl cyclopropylsilanes was also reported 78) and involves the allylation of a postulated cuprate formed by the addition of lithium dibutyl cuprate to a-lithiocyclopropylsilane (Scheme 26). 

A number of cyclopropyl sulfides have been prepared from other cyclopropanes by reactions involving cleavage of a bond from one of the cyclopropyl carbons to hydrogen, halogens, and, in a few cases, a chalcogen moiety. 

A large number of halogenated cyclopropanes have been converted to cyclopropyl sulfides (Table 14) there is one example of the formation of a sulfinic acid. A variety of methods have been used utilizing both nucleophilic and electrophilic cyclopropane species and there are also the possibility of carrying out formal substitution by elimination/addition reactions. 

Nucleophilic substitutions have also been carried out by irradiating mixtures a of a bromocyclo-propane, benzenethiol, and ammonia. When 7-bromobicyclo[4.1.0]heptane and 1-bromo-l-chloro-2,2,3,3-tetramethylcyclopropane were photolyzed under these conditions replacement of the bromine with the phenylsulfanyl group takes place, but the yields of the corresponding cyclopropyl sulfides 9 and 10 were low. Mechanistic studies support a radical chain mechanism for the reactions. ... 

In one case, a cyclopropane with one C-S bond has been converted to a cyclopropyl sulfide with another C-S bond. When 2-methylene-1-phenylsulfinylcyclopropane was allowed to react with a suspension of potassium benzylsulfanate and potassium rerr-butoxide in tetrahydrofuran, l-benzylsulfanyl-2-methylenecyclopropane (2) was formed in 59% yield. °... 

A large number of cyclopropanes have been synthesized from cyclopropyl sulfones, cyclopropyl sulfoxides and cyclopropyl sulfides by taking advantage of the acidity of the cyclopropyl proton a to the C-S bond. Butyllithium is used almost exclusively as the base. The cyclopropyl anions obtained are capable of reacting with alkyl halides, aldehydes, enamines, epoxides, esters. 

The sulfonium fluorosulfonates 45 are very useful precursors for functionalized cyclopropyl sulfides. The reaction of these salts with aliphatic alcohols gave mixed acetals (e.g. 47) in quantitative yield, while phenol reacted as both an oxygen and carbon nucleophile. Benzenethiol and potassium fluoride provide the expected substitution products (e. g. 50 and 51, respectively), however, these are accompanied by side products such as methylated reagent [(methylsul-fanyl)benzene] or l,l-bis(methylsulfanyl)cyclopropane. Quite surprisingly, these substitution reactions fail with strong nucleophiles such as alkoxides, thiolates and azide. 

Methylation of a cyclopropyl sulfide occurred on reaction of 1-methylsulfanylcyclopropane- rani-l,2-dicarboxylic acid with methyl p-toluenesulfonate in formic acid. ° ... 

Treatment of cyclopropyl sulfides bearing a hydroxy group in the side chain with ceric ammonium nitrate (CAN) in methanol gives five- and six-membered cyclic ethers.In this reaction, the formation of cyclic ethers is understood by assuming a single electron transfer mechanism, which involves ring opening of the cation intermediate followed by intramolecular nucleophilic addition. 

Cleavage of cyclopropyl sulfides. Oxidative desulfurization of these compounds gives ketones. ... 

Cyclopropyl sulfides are metallated much more easily than dialkyl sulfides. Exclusive ring metallation is observed upon interacting cyclopropyl-SPh with n-BuLi in THF at 0 °C [8]. Using a 1 1 molar mixture of BuLi and f-BuOK in THF and hexane (— 70 °C) we obtained comparable amounts of ring-metallated product and eyclopropyl-S—CH2K [4]. 

Diquinane synthesis. 2-(4-Alkenyl)cyclopropyl sulfides are Uansformed into diquinanes on oxidation with tris(4-bromophenyl)aminium ions in dichloromethane at room temperature. 

A mixture of 7.2 g POCI3 and 6.7 g N-methylformanilide was heated on the steam bath until it was claret red. To this there was added 4.5 g of 2,5-di-methoxyphenyl cyclopropyl sulfide, and the exothermic combination heated on the steam bath for about 5 min. The deep red, bubbling reaction mixture was added to 150 mL H20 and stirred until all oils had been converted into loose solids. These were then removed by filtration, washed with H20, and sucked as dry as possible. They were dissolved in boiling MeOH which, after cooling in an ice-bath, deposited yellow crystals of 2,5-dimethoxy-4-(cyclopropylthio)benzaldehyde that weighed 3.43 g after air drying, and had a mp of 97-99 °C. Anal. (C12H1403S) C,H. 

This mildly exothermic combination turned a bit cloudy, was stirred for 1 h, then trans-ferred with an air-tight syringe to the above-described Et20 solution of the aromatic disulfide. A heavy precipitate formed, and stirring was continued for an additional 0.5 h. The reaction mixture was then poured into H20, the layers separated, and the aqueous phase extracted with CH2CI2. The extracts were pooled, washed with dilute aqueous KOH, and the solvents removed under vacuum. Distillation gave 0.7 g of 2,5-dimethoxyphenyl cyclopropyl sulfide with identical gas chromatographic behavior to the sample prepared by the cyclization of the chloropropylthio compound. 

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