Silyl radicals theoretical studies

A theoretical study of the reactivity of prototype ketene CH2=C=0 with several radicals including HsSi has been reported. Scheme 5.11 shows that three adducts are possible with the corresponding energy barriers for their formation calculated at B3LYP/6-31G level of theory [75]. However, all the levels of theory used in this study predicted that silyl radical prefers to add to the carbon terminus of ketene. 

M. Guerra, /. Am. Chem. Soc., 115, 11926 (1993). Theoretical Study of the Effect of a-Substituents on the 29Si hfs Constant in Silyl Radicals An Electronic Rather than Structural Effect. 

Theoretical aspects of silyl radicals RsSi were reviewed earlier by Apeloig7. Recent developments in the chemistry of silyl radicals are reviewed in a chapter by Chatgilialoglu and Schiesser in this book29. Experimental studies of tricoordinate MR3 radicals of heavier group 14 elements (M = Ge, Sn and Pb) are reviewed by Mochida482. 

Bottoni A. Theoretical study of the hydrogen and chlorine abstraction from chloromethanes by silyl and trichlorosilyl radicals a comparison between the Hartree-Fock method, perturbation theory, and density functional theory. J Phys Chem A 1998 102(49) 10142-10150. 

Photocyclisation of 8-alkoxy-l,2,3,4-tetrahydro-l-naphthalenones and 4-alkoxy-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ones gives naphtho[l, 8-bc]furans and cyclohepta[cd]benzofurans respectively, and conformational and substituent effects of 1,5-biradicals in the cyclisation process are discussed." " The same authors also describe substituent effects on the photocyclisation of ethyl 2-(8-oxo-5,6,7,8-tetrahydro-l-naphthyloxy)acetates and ethyl 2-(5-oxo-6,7,8,9-tet-rahydro-5H-benzocyclohepten-4-yloxy)acetates to give naphtho[l,8-bc]furans and cyclohepta[c,d]benzofurans respectively." Also reported are cyclisations involving photogenerated radical cations of unsaturated silyl enol ethers, fragmentation cyclisations of unsaturated ot-cyclopropyl ketones which occur by photoelectron transfer and give polycyclics, and kinetic and theoretical studies of [2+3] cycloadditions of nitrile ylids. These reactions have been studied mechanistically and their synthetic potential investigated. 

Silyl radicals have been studied theoretically less extensively than the corresponding cationic species336. Naturally, the most studied species is the parent H3Si. Calculations at all levels of theory find H3Si to be pyramidal (C3v symmetry) with a HSiH angle ranging from 107.2o265g to 115.1°68 281-307 33s exceuent summary of the calcu-... 

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