Intramolecular homolytic aromatic substitution of alkyl 2-benzimidazolyl sulfones as a means of entry into alkyl radicals for organic synthesis
作者:David Crich、Daniel Grant
DOI:10.1016/j.tetlet.2008.02.174
日期:2008.4
radical aromatic substitution of heteroaryl sulfones by tethered aryl radicals has been investigated as a source of alkyl radicals. The 1-(2-iodobenzyl)benzimidazole-2-sulfonyl system was found to be the most effective, while a tetrazole-based system did not undergo the desired radical aromatic substitution at all. Application of the benzimidazole-based system to the generation of alkyl radical and their
PhSeSiR<sub>3</sub>-Catalyzed Group Transfer Radical Reactions
作者:Ganesh Pandey、K. S. S. P. Rao、K. V. Nageshwar Rao
DOI:10.1021/jo000128z
日期:2000.7.1
A novel design for initiating radical-based chemistry in a catalytic fashion is described. The design of the concept is based on the phenylselenyl group transfer reaction from alkyl phenyl selenides by utilizing PhSeSiR3 (1) as a catalytic reagent. The reaction is initiated by the homolytic cleavage of -C-Se- bond of an alkyl phenyl selenide by the in situ generated alkylsilyl radical (R3Si.), obtained by the mesolysis of PhSeSiR3](.-) (1(.-)). The oxidative dimerization of counteranion PhSe- to PhSeSePh functions as radical terminator. The generation of 1(.-) is achieved by the photoinduced electron transfer (PET) promoted reductive activation of 1 through a photosystem comprising of a visible-light (410 nm)-absorbing electron rich DMA as an electron donor and ascorbic acid as a co-oxidant (Figure 1). The optimum mole ratio between the catalyst 1 and alkyl phenyl selenides for successful reaction is established to be 1:10. The generality of the concept is demonstrated by carrying out variety of radical reactions such as cyclization (10, 15-18), intermolecular addition (25), and tandem annulations (32).
PADWA, A.;NIMMESGERN, HILDEGARD;WONG, G. S. K., J. ORG. CHEM., 1985, 50, N 26, 5620-5627
作者:PADWA, A.、NIMMESGERN, HILDEGARD、WONG, G. S. K.
DOI:——
日期:——
PADWA, A.;NIMMESGERN, H.;WONG, G. S. K., TETRAHEDRON LETT., 1985, 26, N 8, 957-960