Mild Method for the Selective Esterification of Carboxylic Acids Based on the Garegg−Samuelsson Reaction

Abstract

A mild method for the selective esterification of primary alcohols is described. The use of different phosphines, I(2), and imidazole allows the selective esterification of a wide variety of acids with excellent results. The generation of a bulky phosphonium-carboxylate salt as intermediate could justify the selectivity observed in this process. Additionally, amides also can be synthesized with use of this method.

Liquid crystalline polyamines containing side dendrons: Toward the building of ion channels based on polyamines

“…After 10 min 0.1 g (1 mmol) of the model compound N,N-dimethyl-2-hydroxyethylamine (DMHEA) was added and then the reaction mixture was stirred at room temperature for 20 h. The resulting solid was purified by column chromatography using toluene as an eluent to yield of 32%. [22]. To a solution of 2 g (8 mmol) I 2 in dry dichloromethane (30 ml), 2 g (8 mmol) triphenylphosphine (PPh 3 ) was added, giving a brown Scheme 1.…”

“…Morcillo and coworkers [22] developed a method for the esterification/amidation of carboxylic acids based on the Garegge Samuelsson reaction [24], which proposes the formation of an alkoxyphosphonium intermediate that suffers the nucleophilic attack to generate an iodo compound. In our case, by reaction with the model compound we were able to obtain compound 4 with 47% yield.…”

Rapid Dehydroxytrifluoromethoxylation of Alcohols

“…CDCl 3 was then used as the reaction solvent to determine what the Ph 3 P/ICH 2 CH 2 I system would be transformed into. After stirring the mixture at room temperature for 15 hr, three phosphorus species were observed, which were determined to be iodophosphonium salt B [Ph 3 P + I I − ] (Garegg et al., 1987, Morcillo et al., 2011), triphenylphosphine, and diiodotriphenylphosphane C (Ph 3 PI 2 ) (Garegg et al., 1987) based on the reported corresponding phosphorus signals (Figure 1B). ICH 2 CH 2 I was almost completely converted into CH 2 =CH 2 , as detected by 1 H NMR spectroscopy.…”

“…ICH 2 CH 2 I was almost completely converted into CH 2 =CH 2 , as detected by 1 H NMR spectroscopy. The large amount of Ph 3 P that remained was because of the reversible equilibrium between Ph 3 P and Ph 3 PI 2 (Ph 3 PI 2 ⇄Ph 3 P + I 2 ) (Morcillo et al., 2011), otherwise Ph 3 P would have been almost fully consumed.

Figure 1 31 P NMR Spectra of the Ph 3 P/ICH 2 CH 2 I Reaction System

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“…As it has been reported that iodophosphonium salt B (Ph 3 P + -I I − ) could also be formed by the reaction of Ph 3 P with I 2 (Morcillo et al., 2011, Pathak and Rokhum, 2015), I 2 was then used instead of ICH 2 CH 2 I in the dehydroxytrifluoromethoxylation reaction (Scheme 7). Desired products were obtained for the conversion of both benzyl alcohol 1a (Equation 1) and alkyl alcohol 1a’ (Equation 2), further supporting the proposed mechanism.…”