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Issue 54, 2016, Issue in Progress
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Isomerizable (E/Z)-alkynyl-O-methyl oximes employing TMSCl–NCS in chlorinative cyclization for the direct synthesis of 4-chloroisoxazoles

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Abstract

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 (Cl2) 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.

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

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Article information


Submitted
12 Apr 2016
Accepted
08 May 2016
First published
09 May 2016

RSC Adv., 2016,6, 48666-48675
Article type
Paper

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

W. Kaewsri, C. Thongsornkleeb, J. Tummatorn and S. Ruchirawat, RSC Adv., 2016, 6, 48666
DOI: 10.1039/C6RA09396E

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