Triethylsilyl radicals

Figure 4.13. Second-order rate constants for reactions of tributylstannyl and triethylsilyl radicals with various alkyl halides at ambient temperature. [Data from (74) and (80).]...

The interaction between oximes and triethylsilyl radical has been investigated by ESR, which showed that an a-silylated hydroxylamine is formed. In spite of the lack of any further detail, this reaction may constitute an excellent access to this type of SMA... 

Triethylsilyl radicals react with COF, in cyclopropane solution to give a siloxy derivative, which was characterized by e.p.r. spectroscopy [1175] ... 

Kinetic EPR spectroscopy has been used for determining absolute rate constants for addition of diethoxyphosphonyl, phenyl and triethylsilyl radicals to thiophene <83JOC3704>. The data show that the reactivity of thiophene and furan towards these radicals is intermediate between those of simple alkenes and benzene. 

Pentafluorobenzenesulphonyl fluoride, which may be obtained from the chloride and xenon difluoride,brings about inactivation of the enzyme oc-chymotrypsin, and the kinetics of this process have been studied (other fluorine-containing sulphonyl fluorides were also involved). The e.p.r. spectrum of (inter alia) the radical CsFs SOa, produced from the chloride by abstraction with triethylsilyl radicals, has been reported and the hyperfine splitting constants have been measured at —40 °C, but unambiguous assignments were not possible. Pentafluorophenylsulphonyl... 

Br-atom abstraction with triethylsilyl radicals/ DTBPrtriethylsilane... 

A number of photochemical approaches are possible to generate sulfonyl radicals in fluid solutions. A traditional method for production of high concentrations of sulfonyl radicals is based on chlorine atom abstraction from sulfonyl chlorides by trialkyIsilyl radicals [61, 62]. The rate constants for chlorine atom abstraction by triethylsilyl radical from methane and benzene sulfonyl chlorides were reported to be 3.2 x 10 M s and 4.6x 10 M s", respectively [63] ... 

The study of the reactivity of trialkylsilyl radicals in solution has been placed on a firmer foundation by the measurement of absolute rate constants for some reactions of triethylsilyl radicals (generated by the reactions of tert-butoxyl radicals with triethylsilane), with some organic halides and benzil/ These data show for example, the greater reactivity of Et3Si in halogen abstraction than that of trialkyltin radicals. Kinetic isotope effects (kn/fco) for the insertion of photochemically generated dimethylsilylene and methylphenylsilylene into Si-H and 0-H single bonds are about 1.3 and 2.1 - 2.3, respectively. The preferred mechanism for insertion of silylenes into O-H bonds is shown in equation (1). Other workers haye shown that dimethylsilylene inserts preferentially into O-H bonds of alcohols compared with S-H bonds in silanes or Si-O bonds in alkoxy-silanes. ... 

The ability of triethyl silyl radicals to remove the strongly bound vinylic chlorine from trichloroethylene (reaction 54) is a characteristic feature of the reactions of triethylsilyl radicals with other chloroethylenes. Radical addition to acetylenes is the method used most frequently to generate vinyl radicals. The formation of vinyl radicals by Cl atom transfer from chloroethylenes to silyl radicals thus offers an interesting alternative to this oaethod. 

Various Physical Properties.—E.s.r. spectra of some 5-substituted 2-thienyl nitroxides, generated by scavenging triethylsilyl radicals with substituted nitro-thiophens, and nitro-anions, have been recorded in order to determine the effective substituent delocalizing power with respect to an unpaired electron in the thiophen series. Triethylsilyloxy nitroxide radicals of thiophen have been produced... 

---