A Simple, Efficient, Green, Cost Effective and Chemoselective Process for the Esterification of Carboxylic Acids

Abstract

Carboxylic acids have been esterified under mild and solvent-free conditions in high yield and purity using the green reagents, dimethyl carbonate and diethyl carbonate, under acid catalysis. The present methodology is free of the disadvantages of base catalysis described earlier, such as high temperatures, use of autoclaves, use of the expensive DBU as base in stoichiometric amounts and the carbonate as solvent. High chemoselectivity is observed in the case of hydroxybenzoic acids.

Methylation with Dimethyl Carbonate/Dimethyl Sulfide Mixtures: An Integrated Process without Addition of Acid/Base and Formation of Residual Salts

“…The methylation of benzoic acids is usually accomplished by reacting them with MeOH in the presence of a strong acid. DMC has been proposed as a safer methylating agent for this transformation and has been used in combination with base catalysts [69][70][71][72] or acid catalysts [73][74][75] for this purpose. In contrast, we obtained excellent yields of methyl esters (entries 1-3, Table 5) by treating benzoic acids under identical methylation conditions to those we used to methylate phenol compounds.…”

Recent advances in methylating agents

“…自Catellani课题组 [35] 1997年报道钯/降冰片烯 图 5 对甲苯磺酸甲酯与烷基溴、芳基酰氯的交叉偶联反应(网络版彩图) 学中的应用. 碱 [43,44] 、酸催化剂 [45,46] 以及极性非质子 溶剂DMF和DMSO [47,48] 都可以有效地活化DMC, 实现 较为温和条件下的转化.…”

Efficient Microwave-Assisted Synthesis of Methyl 4- or 5-Nitro­anthranilate

“…11 However, these processes suffer from major drawbacks including the use of concentrated strong acids, toxic and/or non-ecofriendly solvents, and toxic and/or expensive reagents, or metals. [12][13][14][15][16][17][18][19][20] They are often not suited to use on a large scale and are not environmentally compatible, according to green chemistry rules. 21…”

“…In EtOH, the esterification reaction of 1a did not allow complete conversion of the substrate (possibility because of transesterification). In DMC, which is particularly attractive because it is regarded as a nonvolatile organic compound (VOC) due to its low vapor pressure, 18 product 3a was obtained in 79% yield. Nevertheless, under our reaction conditions, this solvent was ruled out because of an increase in the pressure in the sealed tube, even after cooling, due to degradation of DMC into 1,2-dimethoxyethane (DME), carbon dioxide (CO 2 ), and methanol (MeOH), which is known to occur at a temperature of 90 °C and above.…”