JULIA-KOCIENSKI APPROACH TO 4-SUBSTITUTED 1- ALKENYL-1H-1,2,3-TRIAZOLES

Author

Kunga Tsetan, CUNY City CollegeFollow

Date of Award

2016

Document Type

Thesis

Department

Chemistry

First Advisor

Barbara Zajc

Second Advisor

Mahesh Lakshman

Third Advisor

Urs Jans

Keywords

triazole, cycloaddition, olefination

Abstract

A modular approach to the synthesis of 4-substituted N-vinyltriazoles was
developed. The triazole cores were assembled by copper-catalyzed 1,3-dipolar
cycloaddition of 1-phenyl-1H-tetrazol-5-yl (PT) azidomethyl sulfide with: pmethoxyphenyl, 2-pyridyl, and triisopropylsilyl alkynes. Subsequent oxidation of the sulfides furnished 4-substituted triazoles with a Julia-Kocienski olefination handle attached at the N1 atom of the triazole. Olefination reactions of triazole-derived Julia-Kocienski reagents with paraformaldehyde gave 1-ethenyl-1H-1,2,3-triazoles. Heck reactions of these products with phenyl or p-methoxyphenyl iodide led to further functionalization of the terminal carbon, with E/Z-olefin ratios ≥ 92%. Heck reaction with p-cyanophenyl iodide gave low conversion, and that with 2-thienyl iodide did not proceed. On the other
hand, Julia-Kocienski olefinations proceeded with electron-rich and electron-deficient aryl, as well as alkyl aldehydes. The resulting 1,2-disubstituted alkenes were formed in good yields, but with moderate to poor E/Z-selectivities. A modular approach to the synthesis of 4-substituted N-vinyltriazoles was
developed. The triazole cores were assembled by copper-catalyzed 1,3-dipolar
cycloaddition of 1-phenyl-1H-tetrazol-5-yl (PT) azidomethyl sulfide with: pmethoxyphenyl, 2-pyridyl, and triisopropylsilyl alkynes. Subsequent oxidation of the sulfides furnished 4-substituted triazoles with a Julia-Kocienski olefination handle attached at the N1 atom of the triazole. Olefination reactions of triazole-derived Julia-Kocienski reagents with paraformaldehyde gave 1-ethenyl-1H-1,2,3-triazoles. Heck reactions of these products with phenyl or p-methoxyphenyl iodide led to further functionalization of the terminal carbon, with E/Z-olefin ratios ≥ 92%. Heck reaction with p-cyanophenyl iodide gave low conversion, and that with 2-thienyl iodide did not proceed. On the other hand, Julia-Kocienski olefinations proceeded with electron-rich and electron-deficient aryl, as well as alkyl aldehydes. The resulting 1,2-disubstituted alkenes were formed in good yields, but with moderate to poor E/Z-selectivities.

Recommended Citation

Tsetan, Kunga, "JULIA-KOCIENSKI APPROACH TO 4-SUBSTITUTED 1- ALKENYL-1H-1,2,3-TRIAZOLES" (2016). CUNY Academic Works.
https://academicworks.cuny.edu/cc_etds_theses/610