New Ideas for a 160 Years-Old Reaction

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

“…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 Tribromoisocyanuric acid (TBCA, X = Br), although not yet widely commercially available, can be easily obtained from cyanuric acid, KBr and oxone, in a safe procedure.…”

“…Therefore, depending on the nature of the nucleophile reacting with these electrophilic agents, different products can be obtained, such as haloarenes, halohydrins, halocarbonyls, etc. 1,5,6 The trihaloisocyanuric acids also are very interesting reagents from the Green Chemistry point of view, since they present good atom economy and are safe to be handled. After the reaction is completed, its by-product, the isocyanuric acid can be easily separated from the reaction media by simple filtration and can be reused for the synthesis of new TXCA batches.…”

Superelectrophiles in ring-forming reactions

“…In a 1964 paper, Staskun described the influence of excess H 2 SO 4 or AlCl 3 on the cyclizations of β-ketoamides (the Knorr reaction). 1 He suggested the enhanced yields for the Knorr reaction -in the presence of excess acid -is likely due to the multiple protonations of the dicarbonyl compound. This represented the first mention of highly ionized electrophiles in acid-promoted reactions and it was a predecessor of the superelectrophilic reactivity theory.…”