Cyclo-butyl radical

Radical [3 + 2 cycloaddition. Cyclopentanes can be prepared by addition of alkenes across vinylcyclopropanes catalyzed by phenylthio radicals formed from (C6H5S)2 and AIBN. A Lewis acid such as A1(CH3)3 can increase the rate and the stereoselectivity of this radical initiated cycloaddition. Thus the combination of the vinylcyclopropyl ester 1 with f-butyl acrylate (2) provides the four possible cyclo-... 

The sequential treatment of ( , )-l-tosylamido-2, 4-alkadienes with n-butyl-lithium and propynyliodonium triflate 30 results in a cascade addition/bicy-clization sequence leading to bicyclic N-tosyldihydropyrroles 39 (Scheme 60) [165,166]. These transformations are completely stereoselective for the cis-isomers, and appear to proceed by intramolecular addition of alkylidenecarbene intermediates to the C2-C3 double bond of the pentadienyl chain to give azabi-cyclo[3.1.0]hexenes, which rearrange to 39 through diyl radical species. 

Irradiation at 350 nm of 1,1-dibromocyclopropanes dissolved in liquid ammonia or dimethyl sulfoxide in the presence of sodium benzenesulfanate leads to l,l-bis(phenylsulfanyl)cyclo-propanes. The yields are in all cases below 50% which is due to both decomposition of the product on longer irradiation and formation of significant amounts of cyclopropyl phenyl sulfide. Most 1,1-dichlorocyclopropanes are unreactive, and no reaction occurs in the presence of oxygen, di- erf-butyl nitroxide and 1,3-dinitrobenzene, which supports the notion that the reaction is a radical process. The cleanest reaction took place during irradiation of 2,2-dichloro-1 -methylcyclopropanecarbonitrile, which gave no sulfide, little unreacted starting material, and 1-methyl-2,2-bis(phenylsulfanyl)cyclopropanecarbonitrile (4) in 47% yield. 

In a similar manner 1,3-di-ferf-butyl-2-phenylcyclopropenc (4) gave both di- ert-buty 1- and tert-butyl(phenyl)acetylenes, as well as an enone derived from the normal epoxidation of the cyclo-propene double bond. The mechanism by which the alkynes are formed is not clear, although radical scavengers did not significantly affect the reaction and addition of acetate did not lead to this being incorporated. 

It has been established that the decomposition of cumene hydroperoxide in the presence of thiolsulfinate occurs primarily via a polar process (1). However, a homolytic process may be involved in the conversion of the thiolsulfinate to the active peroxide decomposer. This was probed by adding the radical inhibitors /2-naphthol and 2,6-di-tert-butyl-4-methylphenol (see Figure 5). The inhibitors totally suppressed the decomposition of hydroperoxide by thiolsulfinate. In contrast to /3-naphthol and 2,6-di-terf-butyl-4-methylphenol, the addition of cyclo-hexanol had no significant effect. Similarly, the addition of methanol only reduced the decomposition of hydroperoxide by the thiolsulfinate by 1% after 186 hr. 

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