Arylcyclopropane

A similar reaction takes place with sulfuric acid. It takes 2 to 3 months to achieve thermodynamic equilibrium between 5- and 6-membered heterocycles. However, the ratio of the products may be easily predicted in several minutes measuring the ratio of intensities of peaks of [M — CH3]+ and [M — C2H4]+ ions in an El mass spectrum of the initial substituted arylcyclopropane [23]. 

Acetylarenes are converted into l,l-dichloro-l-arylcyclopropane-2-carboxylic acids or 2-arylpropionic acids via the initial formation of propenoic acids [16, 17]. 

Photochemical addition of SOj to arylcyclopropanes have reportedly produced the two isomers 114 and 115. ... 

Hesse, Org. Syn., 50, 66 (1970)]. The checkers standardized the solution immediately before use by diluting a 2.5-ml. aliquot with 10 ml. of benzene and titrating with alM solution of 2-butanol in xylene according to the procedure of Watson and Eastham3 [see M. Gall and H. O. House, Org. Syn., 52, 39 (1972)], with 1,10-phenanthroline as indicator. The submitters report that the yield of arylcyclopropane is lower if a commercially available solution of butyllithium in hydrocarbon solvents is used. 

Treatment of a variety of a,/i-unsaturated carbonyl compounds with zinc and 1,2-bis(chlorodimethylsilyl)ethane leads to the formation of organozinc carbenoids which may be trapped with olefins to give alkenyl- and arylcyclopropanes (equation 78)131. With... 

A study of the photo-sensitized ring-opening reactions of the radical cations (76) of arylcyclopropanes (75) with methanol, water, and cyanide nucleophiles suggests a three-electron 5k2 mechanism (Scheme 11).185 The isolated products are methyl propyl ethers, derived from nucleophilic attack of methanol on the radical cation (76). They were detected by UV-VIS spectroscopy and shown to react with nucleophiles by transient kinetic methods. The benzyl radical (77) reacts with the DCB radical anion to afford monoaromatic ether (78) by oxidation and protonation or the disubstituted ether (79) by addition of DCB. Regio- and stereo-selectivity of the substitution were complete regiochemistry and rate constant were profoundly effected by the electronic nature of the aryl substituents.186 Elsewhere, a combined ab initio and CIDNP study... 

One of the most prominent manifestations of this effect consists of the oxidation of 1,2-di-arylcyclopropane (CP) with oxygen in the presence of photoexcited 9,10-dicyanoan-thracene (DCNA) in acetonitrile (Mizuno et al. 1987) (Scheme 5-12). 

Arylcyclopropanes and their heterocyclic analogues are liable to electron transfer induced fragmentation of a carbon-carbon bond that in some cases leads to synthetically useful products. Thus, 1,2-diarylcyclopropanes [240-243] as well as 2,3-diaryloxirans [244-246] and -aziridines (in the last case, also 2-monophenyl derivatives) [247,248] are cleaved upon photoinduced electron transfer sensitization. The final result, after back electron transfer, is trans-cis isomerization of the ring. In the presence of a suitable trap, however, a cycloaddition reaction takes place, involving either the radical cation or the ylide. Thus, dioxoles, ozonides or azodioxoles, respectively, are formed in the presence of oxygen and oxazolidines have been obtained from cyclopropanes in the presence of nitrogen oxide (Sch. 23). 

When ct-selanylalkyllithium compound 123 is reacted with double bonds of type 124, a methaneselenolate displacement generates functionalized arylcyclopropane derivatives 125.210 Depending on the substituents R1 and R2, the ratio of 125a 125b can vary from 97 3 to 0 100 as shown in Table 4 (Scheme 31). 

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