Characterization of the Structure of tert-butyl[1-hydroxy-2-methyl-3-(1H-1,2,4-triazol-1-yl)]propan-2-ylcarbamate Using 2D Heteronuclear NMR Experiments

Younas Aouine

International Journal of Experimental Spectroscopic Techniques

Characterization of the Structure of tert-butyl[1-hydroxy-2-methyl-3-(1H-1,2,4-triazol-1-yl)]propan-2-ylcarbamate Using 2D Heteronuclear NMR Experiments

Younas Aouine¹, Hassane Faraj¹, Anouar Alami^1*, Abdelilah El-Hallaoui¹ and Mohamed Akhazzane²

¹Laboratoire de Chimie Organique Fès, Faculté des Sciences Dhar El Mahraz, Université Sidi Mohamed Ben Abdellah, Morocco
²Cité de l'innovation, Université Sidi Mohamed Ben Abdellah, Fès, Morocco

^*Corresponding author

Anouar Alami, Laboratoire de Chimie Organique Fès, Faculté des Sciences Dhar El Mahraz, Université Sidi Mohamed Ben Abdellah, Morocco, Tel: +212-661 796 480, Fax: +212-535 733 171, E-mail: [email protected]

Int J Exp Spectroscopic Tech, IJEST-1-004, (Volume 1, Issue 1), Review Article

Received: January 12, 2016
Accepted: March 12, 2016
Published: March 16, 2016

Citation: Aouine Y, Faraj H, Alami A, El-Hallaoui A, Akhazzane M (2016) Characterization of the Structure of tert-butyl[1-hydroxy-2-methyl-3-(1H-1,2,4-triazol-1-yl)]propan-2-ylcarbamate Using 2D Heteronuclear NMR Experiments. Int J Exp Spectroscopic Tech 1:004

Copyright: © 2016 Aouine Y, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Abstract

The alkylation of 1H-1,2,4-triazole with an O-tosyloxazoline derivative, followed by an oxazoline ring-opening reaction and protection of amine function, leads normally to obtain two regioisomers of β-aminoalcohols. After purification by column chromatography of the crude reaction product, only a single product is obtained. Hence, there is need of its identification by spectroscopic study.

Keywords

Oxazoline, 1H-1,2,4-triazole, β-aminoalcohol, 2D heteronuclear NMR experiments

Introduction

Triazoles constitute an important class of biologically active heterocyclic compounds that have received a great deal of attention since their discovery. Diverse compounds derived from 1,2,4-triazoles have a wide spectrum activities, including antimicrobial [1,2] and antibacterial properties [3,4], human antifungal agents [5], anticancer agents [6], antiviral [7], antitumor activity [8] and in agricultural science as potent fungicides, herbicides and insecticides [9,10]. Amino acids containing the 1,2,4-triazole moiety and their derivatives represent a well-known group of organic compounds also presenting biological activity. Thus β-(1,2,4-triazol-1-yl)-L-alanine is known as an important metabolite in plants of the fungicide myclobutanil [11-13] and β-(3-amino-1,2,4-triazol-1-yl)-L-alanine is a metabolite of the weed killer 3-amino-1,2,4-triazole [14].

Materials and Methods

NMR spectra (¹H, ¹³C and ¹⁵N) were recorded on a Bruker AM 300 (operating at 300.13 MHz for ¹H, at 75.47 MHz for ¹³C and at 30.41 MHz for ¹⁵N) spectrometer (Centre Universitaire Régional d'Interface, Fez-Morocco). NMR data are listed in ppm and are reported relative to tetra-methylsilane (¹H, ¹³C).

Discussion

It is reported that afforded the corresponding 1- and 4-alkylated isomers, with prevalence of the N1-isomer [15-17]. Reaction of 1H-1,2,4-triazole with 1 and K2CO3, was carried out in the presence of a catalytic amount of tetrabutylammonium bromide in N,N'-dimethylformamide at 120°C for 12 hours. The previous reaction stage is followed by an oxazoline ring-opening reaction carried out in acidic medium. The aminoalcohol derivative 2, which is the aim of this paper, is obtained after addition of tert-butoxycarbonyl anhydride Boc to the intermediate product in a mixture of water/dioxane (1/2) at (0 < T < 5°C) in the presence of triethylamine [18]. Its structure was established on the basis of NMR spectroscopy (¹H, ¹³C and ¹⁵N), in addition to MS data and elemental analysis.

The definite assignment the chemical shifts of protons, carbons and nitrogens of compound 2 are shown in table 1 and table 2 (Figure 1, Figure 2 and Figure 3).

Table 1. ¹H (300 MHz) and ¹³C (75.47 MHz) NMR spectral data for 2 in DMSO-d6, including results obtained by homonuclear 2D shift-correlated ¹H COSY and heteronuclear 2D shift-correlated HMQC (¹J_CH)^a. Chemical shifts (δ, ppm) and coupling constants (J, Hz, in parenthesis)^b.

Table 2. Listing of ¹⁵N (400 MHz) NMR spectral data for 2 inDMSO-d6, including results obtained by heteronuclear single quantum coherence shift-correlated (HSQC) and heteronuclear multiple bond coherence shift-correlated (HMBC).

This interaction ¹H-¹⁵N has allowed us to make the following observations:

- A signal at 93.29 ppm attributed to the carbamate nitrogen N-1: correlation between CH3, CH2-triazole and the amidic nitrogen.

- A signal at 214.54 ppm attributed to the N-7 of the 1,2,4-triazole ring: correlation between the two triazole protons, CH2-triazole and N-7 nitrogen at position 1 of the 1,2,4-triazole ring.

- A signal at 251.97 ppm attributed to the N-10 of the 1,2,4-triazole ring: interaction between the two triazole protons and the N-10 located in the position 4 of the 1,2,4-triazole ring.

- A signal at 299.12 ppm attributed to N-8 of the 1,2,4-triazole ring: interaction between CH2-triazole, triazole proton H-9 and N-8 at position 2 of the 1,2,4-triazole ring.

Further, the analysis of ¹H-¹⁵N HMBC spectrum of compound 2 confirms that the nucleophilic substitution reaction of 1,2,4-triazole and O-tosyloxazoline derivative 1 is carried out on the nitrogen in position 1 of the 1,2,4-triazole ring and its structure has been clearly identified (Figure 4).