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Isomerizable (E/Z)-alkynyl-O-methyl oximes employing TMSCl-NCS in chlorinative cyclization for the direct synthesis of 4-chloroisoxazoles

机译:在化学环化中使用TMSC1-NCS的可异构化(E / Z)-炔基-O-甲基肟,用于直接合成4-氯异恶唑

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摘要

For the first time, 4-chloroisoxazoles are directly synthesized in moderate to excellent yields from (E/Z)-alkynyl-O-methyl oximes via chlorinative cyclization. The synthesis employs the combination of N-chlorosuccinimide (NCS) and chlorotrimethylsilane (TMSCl) in nitromethane solvent where chlorine (Cl-2) and hydrochloric acid (HCl) are generated in situ. In addition, the current protocol is applicable to the synthesis of 4-bromo- and 4-iodoisoxazoles when N-bromosuccinimide (NBS) and N-iodosuccinimide (NIS), respectively, are employed in place of NCS. The current method can improve the overall efficiency of the preparation of 4-haloisoxazoles starting from the step where alkynyl-O-methyl oximes are prepared since (E)-isomers can isomerize and cyclize under the conditions.
机译:第一次,通过氯化环化反应,由(E / Z)-炔基-O-甲基肟直接以中等至优异的产率直接合成了4-氯异恶唑。该合成方法是在硝基甲烷溶剂中结合使用N-氯代琥珀酰亚胺(NCS)和三甲基氯硅烷(TMSCl),在其中原位生成氯(Cl-2)和盐酸(HCl)。另外,当分别使用N-溴琥珀酰亚胺(NBS)和N-碘琥珀酰亚胺(NIS)代替NCS时,当前方案适用于4-溴和4-碘异恶唑的合成。从制备炔基-O-甲基肟的步骤开始,由于(E)-异构体可在该条件下异构化和环化,因此本方法可提高制备4-卤代恶唑的总效率。

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