A new synthetic route to substituted quinones by radical-mediated coupling of organotellurium compounds with quinones
作者:Shigeru Yamago、Masahiro Hashidume、Jun-ichi Yoshida
DOI:10.1016/s0040-4020(02)00784-6
日期:2002.8
Carbon-centered radicals generated from the corresponding organotellurium compounds react with a variety of quinones under photo-thermal conditions to give the monoaddition product in moderate to excellent yield. The reaction can be used for the synthesis of polyprenyl quinoid natural products and C-glycosides.
Acyl radicals generated from either acyl tellurides or alkyltellurides and carbon monoxide react with isonitriles to give α-acyl-substituted imidoyl tellurides in good to excellent yield. Hydrolysis of the product under oxidative conditions provides the corresponding α-acyl amides.
Synthetic and Theoretical Studies on Group-Transfer Imidoylation of Organotellurium Compounds. Remarkable Reactivity of Isonitriles in Comparison with Carbon Monoxide in Radical-Mediated Reactions
作者:Shigeru Yamago、Hiroshi Miyazoe、Ryuta Goto、Masahiro Hashidume、Takashi Sawazaki、Jun-ichi Yoshida
DOI:10.1021/ja003879r
日期:2001.4.1
Imidoylation of organotellurium compounds with isonitriles has been investigated in conjunction with the radical-mediated C1 homologation reaction by using CO and isonitriles. Carbon-centered radicals generated photochemically or thermally from organotellurium compounds react with isonitriles in a group-transfer manner to give the corresponding imidoylated products. Organotellurium compounds have been found to serve as effective precursors of a wide variety of stabilized radicals, namely benzyl, alpha -alkoxy, alpha -amino, and acyl radicals, which take part in the imidoylation with high efficiency. The reactions are compatible with various functional groups, and can be carried out in various solvents including environmentally benign water. The reactivity of isonitriles has been compared with that of CO through competition experiments, and the results indicate that isonitriles are superior to CO as radical accepters in reactions with stabilized radicals. The origin of the differences has been addressed in theoretical studies with density functional theory calculations using the B3LYP hybrid functional. The calculations suggest that both carbonylation and imidoylation proceed with low activation energies, and that there an virtually no differences in the kinetic sense, instead, it indicates that thermodynamic effects, namely differences in the stability of the acyl and the imidoyl radicals, control the overall course of the reactions.