Master's Theses

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.

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