Chlorophenyl radical

Stronger reducing agents than Cu1 can be used for reactions that are related to the classical Meerwein reaction. Tim salts not only catalyze the formation of aryl radicals from diazonium ions but, as shown by Citterio and Vismara (1980) and Cit-terio et al. (1982 a), in stoichiometric proportions they also reduce the primary aryl-ethane radical to the arylethyl anion, which is finally protonated by the solvent SH (Scheme 10-61). This method is the subject of a contribution to Organic Syntheses (Citterio, 1990), in which 4-(4 -chlorophenyl)buten-2-one is obtained in 65-75% yield from 4-chlorobenzenediazonium chloride and but-3-en-2-one. 

Since the benzene emission in the thermal decomposition of benzoyl peroxide results from radical transfer by the phenyl component of a benzoyloxy-phenyl radical pair, phenyl benzoate produced by radical combination within the same pair should appear in absorption. A weak transient absorption has been tentatively ascribed to the ester (Lehnig and Fischer, 1970) but the complexity of the spectrum and short relaxation time (Fischer, personal communication) makes unambiguous assignment difficult. Using 4-chlorobenzoyl peroxide in hexachloro-acetone as solvent, however, the simpler spectrum of 4-chlorophenyl 4-chlorobenzoate is clearly seen as enhanced absorption, together with... 

Thus, when the radical generated is -chlorophenyl, no dichlorobi-phenyl is formed but only -chlorobiphenyl.55... 

Treated with c. HCl (65JOC2145) or c. H2SO4, then ice (63JOC2828), thianthrene 5-oxide gave 2-substituted-products 2-chloro (in low yield) and 2-hydroxythianthrene 5-oxide, the latter being reduced to 2-hydroxythianthrene by subsequent exposure to Sn/AcOH. Thianthrene radical ion(H-) may be produced in each case thus the incorporation of phenol into the HCl reaction gave the 5-(4-chlorophenyl)thianthrenium chloride (65JOC2145) (see Section III, A, 3, b). 

RuClj(Hcbx)(cbx) (Hcbx=A-2 -chlorophenyl-2-pyridine-carboxamide). This red-brown material is made from the ligand and RuClj, and its X-ray crystal structure determined (Fig. 1.36). The system RuCl2(Hcbx)(cbx)/Oj/M( butyraldehyde/DCE epoxidised a number of cyclic alkenes efficiently at room temperatures (Table 3.1). Addition of the radical trap 2,6-di-ferf-butyl-4-methylphenol stopped epoxidation reactions altogether, suggesting that a mechanism involving radicals is involved [801],... 

Michler s Ketone as the sensitiser and chlorophenyl-bis-trichloromethyltriazine as the radical photoinitiator. In the flexographic plate process the monomers are mono-and multi-fnnctional acrylates, e.g. butanedioldiacrylate, and the photoinitiators are radical prodncers, e.g. benzildimethyacetal, nsing UV-A (350-370 nm) light. 

Particularly in the older literature, a and j3 designations are found. While, in many cases, this designation may simply indicate that the authors isolated two isomeric azoxy compounds of unspecified structure, where the identity of the isomers has been established the a term implies that the NO group is directly attached to the parent radical in the name, i.e., [Pg.429]

Four nitroxyl radicals were attached to a calyx[4]arene.36 In the solid state two of the nitroxyls are in close proximity and exhibit a dipolar splitting, D, of 10 mT, which corresponds to a point dipole distance of about 6 A. Hexaaryl-biimidazoles (HABI) are readily cleaved, either thermally or photochemically, to provide a pair of triarylimidazolyl radicals. UV irradiation of a powder sample of 2,2 -di(ortfco-chlorophenyl)-4,4, 5,5 -tetraphenylbiimidazole (o-Cl-HABI) at 3 K produced a radical pair with D = 0.0111 cm 1 from which r = 6.32 A was calculated.37 Heating of the sample above 20 K or irradiation at 50 K produced a different geometry of the radical pair with D = 0.0103 cm-1, r = 6.26 A. 

Flash photolysis of a substituted hexaarylbiimidazole and reactions of the imi-dazolyl radical. Coraor, G. R., Riem R. H. MacLachlan, A. Urban, E. J. (Exp. Stn., E. I. DuPont de Nemours, and Co., Wilmington, Del.). J. Org. Chem. 1971, 36 (16), 2272-5. (Eng). The rate of reaction of 2-(o-chlorophenyl)-4,5-diphenylimida-zolyl radicals (L with additives was studied in various solvents. Evidence based on measured rate consts., including kinetic D isotope effects, prove that the rate detg. step in the reaction L + aromatic amine is an electron change reaction at the amino N, while in the reaction L + hydroquinone the rate-detg. step is H abstraction. 

Irradiation of 5-(2-chlorophenyl)-l,3-diphenylpyrazole (187) also leads to ring closure and a mechanism has been considered560 in which a 7r-complexed intermediate (188) and a cyclohexadienyl radical (189) play a role (equation 140). 

A transient intermediate has been observed which decays with k = 12.6 s-1 in a first-order process. In view of its long lifetime the transient is supposed to be the cyclohexadienyl radical. A similar reaction mechanism had earlier been proposed for the photochemical cyclization of 5-(2-chlorophenyl)-1,3-diphenyl-1,2,4[1 //]-triazole561. Intramolecular aryl-aryl coupling has also been described for A2-l,2,4-triazol-5(l//)-one derivatives containing an 0-bromophenyl and a heteroaryl substituent in vicinal positions562. 

A photodimerization approach has been applied here. Thus photolysis of 4-(4-chlorophenyl)-thiazoline-2-thione forms the head-to-head dimer (37) <86CC1030>. Under radical conditions 1,3-dioxole forms two geometrical isomers of cyclobutabis-l,3-dioxolane <85CC1088>. 

The reaction seems to proceed through a radical mechanism. Small amounts of difluorides and o-fluorinated products are obtained as byproducts in the reactions of (4-/cr/-butylphenyl)-trimethylsilane and (4-chlorophenyl)trimethylsilane (X = t-Bu and Cl). The yield of o-fluo-rinated compounds increases in the case of (4-methoxyphenyl)trimethylsilane (39%, X = OMe). 1,4-Difluorobenzene (35%) is formed in the reaction of trimethylphenylsilane (X = H) with xenon difluoride. 

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