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

Abstract

The reaction between trihaloisocyanuric acids and alkynes in the presence of acetic acid provides an efficient methodology for preparation of β-haloenol acetates in yields ranging from 34 to 94%, depending on the halogen and alkynes used. This methodology provides an alternative to typical procedures, which usually employ metal catalysis and are limited to terminal alkynes.

Lipophilic Indole-Catalyzed Intermolecular Bromoesterification of Olefins in Nonpolar Media

“…The existence of 1c-Br was evidenced by NMR and HRMS analysis. Unlike other intermolecular bromoesterification reactions, the indole catalytic protocol does not require an excess amount of carboxylic acid. , We speculate that the active species 1c-Br might interact with the carboxylic acid which could facilitate the reaction. Thus, an 13 C NMR experiment on a 1:1 mixture of 1c-Br and benzoic acid ( 7a ) was conducted, and a measurable downfield-shift of the C(2) signal was observed (Figure ).…”

“…Electrophilic halofunctionalization of alkenes is a powerful organic transformation, permitting the simultaneous introduction of a halogen and an additional functional group across an olefinic substrate. The resultant 1,2-halofunctionalized compounds are valuable building blocks that can easily be manipulated by nucleophilic substitution of the halogen. − Olefinic halofunctionalizations such as haloetherifications, − haloamidations, − halo-dearomatization, and haloesterifications − ,− are well-documented. Among these reactions, intermolecular haloesterification is challenging with a low efficiency partly due to the weak nucleophilicity of the carboxylate group.…”

“…Among these reactions, intermolecular haloesterification is challenging with a low efficiency partly due to the weak nucleophilicity of the carboxylate group. Practically, superstoichiometric amounts of carboxylic acid is often required to compensate the low reaction efficiency. , In addition, these reactions are typically run in environmentally unfriendly solvents such as methylene chloride and chloroform. A seminal work on the asymmetric bromoesterification of unactivated olefins was reported by Shi in which the reactions proceeded smoothly with catalyst (DHQD) 2 PHAL in ethyl acetate (Scheme , eq 1) .…”

Metal-Catalyzed Synthesis and Transformations of β-Haloenol Esters

“…In this context, while the utility of α-haloenol esters remains almost unexplored due to the lack of efficient and general synthetic methods [7][8][9][10], more accessible β-haloenol esters have gained significance in recent years as coupling partners in diverse chemical transformations. Several methodologies can be employed for the preparation β-haloenol esters, the most classical ones involving the acylation of haloenolate anions [11][12][13][14][15] or the haloacyloxylation of alkynes employing the elemental halogens [16][17][18][19][20], bis(pyridine)iodonium tetrafluoroborate (IPy2BF4) [21][22][23][24][25], N-halosuccinimides (NXS; X = Cl, Br, I) [26][27][28], PhI(OAc)2 [29][30][31], trihaloisocyanuric acids [32] or N,N-dibromo-p-toluenesulfonamide (TsNBr2) [33] as the electrophilic halogen source (Scheme 1). In this context, while the utility of α-haloenol esters remains almost unexplored due to the lack of efficient and general synthetic methods [7][8][9][10], more accessible β-haloenol esters have gained significance in recent years as coupling partners in diverse chemical transformations.…”

Regio- and Stereoselective Synthesis of Enol Carboxylate, Phosphate, and Sulfonate Esters via Iodo(III)functionalization of Alkynes

“…In light of the above background, difunctionalization of alkynes with halogen and carboxylate, phosphate, or sulfonate groups appears attractive as it allows for the simultaneous and stereoselective installation of the two potential leaving groups onto the CC bond. Indeed, a series of haloacyloxylation reactions, iodoacyloxylation in particular, have been developed using the combination of electrophilic halogen and nucleophilic carboxylate sources for the synthesis of β-haloenol carboxylates . Among them, the method reported by Priebbenow and co-workers employs the combination of iodobenzene dicarboxylate and I 2 for the stereoselective iodoacyloxylation of various alkynes (Scheme a) .…”