Abstract

Objectives: We present a ‘greener’ synthesis for the direct conversion of arylazides into the corresponding trizoles
via phase transfer catalyst-assisted [3+2] cycloaddition in aqueous phase.
Methods: The synthesis of triazoles were approached (Figure 1) based on previously published methods for azide- aldehyde [1] and azide-ketone [2]. In an ordinary glass tube equipped with a magnetic stirring bar, to aldehydes or ketones (0.21 mmol), TBAHS (0.042 mmol) and KOH (0.42 mmol) were added successively in Milli-Q water (1 mL) at RT. Finally, corresponding arylazide (0.21 mmol) was added to above RM. This RM was stirred at RT for 2 minutes which was subsequently heated for 24 h to 48 h at 100 °C. The reaction progress was monitored by TLC and after consumption of starting aldehyde/ketone, RM was cooled to RT. The crude RM was extracted with ethyl acetate and it was dried over Na2SO4, filtered and concentrated. Product 3 was obtained by column chromatography and characterized by using NMR and MS.
Results: Present synthetic approach covering a structurally diverse group of aryl azides 1(a-e) and aldehydes 2(a-b) or ketones 2(g–n) to obtain high yields of varieties of triazoles. In addition, the excellent yields are even more impressive considering that water was the only solvent. Overall, our methodology has proven robust and demonstrated by the preparation of twenty-seven different triazoles, fourteen of them reported for the first time.

Conclusions: We have developed a simple, versatile, and green route for enolate-mediated azide-aldehyde or ketone [3+2]-cycloaddition reaction which enables the synthesis of triazoles containing a variety of functional groups with excellent regioselectivity using water as the only solvent. This water-compatible and phase transfer catalyst- assisted catalytic synthetic approach which provides a stepping stone towards a greener organic synthesis in pharmaceutical industries.

Biography

Dr. Sameer Joshi was born and raised in Pune, India. After finishing my Masters degree with specialization in Organic Chemistry at the University of Pune, India (2009) He joined the National Chemical Laboratory (NCL) also in Pune, where He stayed for 1 & 1/2 years. Then, I spent 2 years working in a private pharmaceutical company in Pune, India. At the beginning of 2013, He was offered the Ph.D. opportunity to become a member of Dr. Llop´s research group at CIC biomaGUNE, Spain. Later, He joined the group in October 2013 and finally He have completed his Ph.D. on June 1st 2017 by working on the development of new strategies for the synthesis of 13N‐labelled compounds. In 2017, I began my first post doctoral position in National Chemical Laboratory (NCL), Pune, India. Here, main objective of the project to achieve click chemistry of triazoles using Azide ‐Aldehydes or Ketones [3+2]‐cycloaddition reactions using water as a green solvent. Presently, He is working as a Research Associate at Wayne State University, Detroit, USA since October 2018. Currently, He is developing the novel radiotracers with F‐18 for HDACs. He have six scientific international publications till date. He presented or participated in five different international conferences and one of my poster presentation in ISRS 2015 was selected as an outstanding poster in University of Missouri, USA. he received European prestigious Marie Curie Fellowship and National Post Doctoral fellowship under my research study.

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