control of the metalation regioselectivity of uracils and uridines. In the absence of the Lewis acid, metalation of uracil and uridine derivatives with TMPMgCl·LiCl occurs at the position C(5). In the presence of MgCl2, zincation using TMP2Zn·2LiCl·2MgCl2 occurs at the position C(6). This metalation method provides easy access to functionalized uracils and uridines. Using TMP2Zn·2LiCl·2MgCl2 also allows to
Pd(II)-catalyzed regioselective direct arylation of uracil via oxidative Heck reaction using arylboronic acids
作者:Biplab Mondal、Somjit Hazra、B. Roy
DOI:10.1016/j.tetlet.2013.12.092
日期:2014.1
A palladium catalyzed regioselective synthesis of 6-aryl uracils via oxidative Heckreaction (C–H bond functionalization) of uracils and arylboronic acids is reported. The method is simple, atom-economical, and high yielding.
Palladium-catalyzed direct 5-arylation of 1,3-dimethyluracil with aryl bromides: an electrophilic metalation–deprotonation with electrophilic arylpalladium intermediate
作者:Ko Hoon Kim、Hyun Seung Lee、Jae Nyoung Kim
DOI:10.1016/j.tetlet.2011.09.066
日期:2011.11
An efficient method of palladium-catalyzed direct 5-arylation of 1,3-dimethyluracil was developed with a various range of aryl bromides including electron-deficient aryl bromides. 5-Aryluracil derivatives were obtained in moderate to good yields regioselectively most likely via an electrophilic metalation–deprotonation process.
Switching the Regioselectivity of Direct C-H Arylation of 1,3-Dimethyluracil
作者:Miroslava Čerňová、Radek Pohl、Michal Hocek
DOI:10.1002/ejoc.200900586
日期:2009.8
An interesting dichotomy in the regioselectivity and mechanism of directC–Harylation of 1,3-dimethyluracil was observed. Its Pd-catalyzed reactions with diverse aryl halides in the absence of CuI lead preferentially to 5-aryluracils, while reactions in the presence of CuI give 6-aryl derivatives as the major products. Cu-mediated reactions (in the absence of a Pd catalyst) proceed with lower efficiency
Photolysis of5-bromo-1, 3-dimethyluracil (5-BDMU) in substituted benzenes afforded the corresponding 5-aryl derivatives together with the unexpected 6-isomers as an isomeric mixture. The 6-isomers were found to be derived from the protonated 5-BDMU, presumably via the interaction between LUMO5-BDMU (in the excited triplet state) and LUMOaryl (in the ground state).