Synthesis of 4- and 5-Substituted 1-Hydroxyimidazoles through Directed Lithiation and Metal−Halogen Exchange
作者:Birgitte Langer Eriksen、Per Vedsø、Mikael Begtrup
DOI:10.1021/jo001554n
日期:2001.12.1
regioselectively at the 4-position of 1-(benzyloxy)imidazole by bromine-lithium exchange of 4-bromo-2-chloro-1-(benzyloxy)imidazoles, protected at C-5 with chloro or trimethylsilyl groups, followed by reaction with an electrophile. The 5-(trimethylsilyl) group was removed via base-catalyzed desilylation. Chlorine at C-2 and O-benzyl groups were removed by palladium-catalyzed hydrogenolysis.
在用氯或三甲基甲硅烷基保护C-2之后,通过在C-5锂化,将亲电试剂选择性地引入1-(苄氧基)咪唑的5-位。随后用亲电试剂处理,得到5-取代的1-(苄氧基)-2-氯咪唑8-13和5-取代的1-(苄氧基)咪唑3-5,在处理过程中失去了2-(三甲基甲硅烷基)基团。通过4-溴-2-氯-1-(苄氧基)咪唑的溴-锂交换将亲电试剂选择性引入1-(苄氧基)咪唑的4-位,然后在C-5处用氯或三甲基甲硅烷基保护,然后与亲电试剂反应。通过碱催化的甲硅烷基化除去5-(三甲基甲硅烷基)基团。通过钯催化的氢解除去C-2和O-苄基上的氯。