Reaction of trihaloisocyanuric acids with alkynes: an efficient methodology for preparation of β-haloenol acetates

Livia T C Crespo,Pierre Mothe Esteves,Geisa P Nogueira,Marcio C S De Mattos,Antigoni Kotali

doi:10.24820/ark.5550190.p010.211

Livia T C Crespo, Pierre Mothe Esteves + Show 3 more

Open Access

https://doi.org/10.24820/ark.5550190.p010.211

Copy DOI

Abstract

Reaction of trihaloisocyanuric acids with alkynes: an efficient methodology for preparation of β-haloenol acetates

Highlights

Trihaloisocyanuric acids (TXCA, Fig. 1) are inexpensive cyclic ureas used as versatile and green electrophilic halogenating agents.[1,2,3,4,5] Among the haloisocyanuric acids, the most employed is the trichloroisocyanuric, or TCCA (X = Cl), a stable solid used for swimming pool disinfection, sold in supermarkets or specialized stores on multigram/kilogram scale.[6]
Continuing our interest on the chemistry of trihaloisocyanuric acids, we have considered the use of TXCA as electrophilic reagent in the reaction with alkynes in order to prepare the interesting β-haloenol acetates, which are synthetically appealing building blocks
In order to obtain the desired β-haloenol acetates, we have reacted selected alkynes with TXCA in the presence of acetic acid, according to the strategy shown in Scheme 2

Summary

Introduction

The use of HOAc as solvent (Table 1, entry 1) afforded the expected β-bromoenol acetate along with minor amount (3%) of the corresponding β-dibromoketone, due to the hydrolysis of the products. The use of 1:1 (v/v) mixture of Ac2O and HOAc afforded only the β-bromoenol acetate in quantitative conversion after 1h (Table 1, entry 4) and 87% isolated yield. Based upon this initial study we chose the 1:1 mixture of HOAc:Ac2O as standard conditions for the reaction of TXCA with other alkynes (2 mmol of substrate, and 0.68 mmol of TBCA in 6 mL of solvent at room temperature).

Results

Conclusion