Green and Efficient Esterification Method Using Dried Dowex H⁺/NaI Approach

Abstract

The usefulness of dried Dowex H + cation-exchange resin with or without sodium iodide (NaI) as a catalyst system for different kinds of esterifications using carboxylic acids and alcohols as starting materials has been systematically investigated. The Dowex H + /NaI approach is very effective, generally high yielding, energy-efficient, and nontoxic, and the Dowex H + resin is reusable. Since the whole procedure from start to product isolation is also very simple, these features make the method environmentally friendly. The method is regioselective, and its potential for separation of valuable carboxylic acids like resin acids from mixtures containing other kinds of carboxylic acids has been demonstrated. Examples for green and straightforward esterification of highly important natural amino acids are also presented.

(E)-Di-iodination of Alkynes Using Dried Dowex H+/NaI Approach

“…Furthermore, the method presented here may open a new way to produce very important radio-iodinated compounds. Ultimately, we believe that our method will become widely used in various kinds of organic syntheses as described in our earlier publications 33−35 and the results presented here.…”

“…All compounds ( 1 – 12 ) are commercially available; however, the ester 7 was prepared using the dried Dowex H + /NaI approach with the catalytic system that we recently reported. 35 We have previously reported the preparation of compound 17 from propargyl alcohol ( 5 ); however, in that case, we used only 1 equiv of NaI in the reaction and obtained a 60% yield. 33 In this paper, 2.05 equiv of NaI was used and the yield improved to 71% since now the propargyl alcohol ( 5 ) conversion to 17 was far more effective (actually the yield was only 30% when 1 equiv NaI was used if the yield was calculated from propargyl alcohol 5 because the di-iodinated product 17 was formed).…”

“…All starting materials ( 1 – 12 ) and the Dowex H + ion-exchange resin used in the study were commercially available; however, isopropyl hex-5-ynoate ( 7 ) was prepared using the method we reported recently. 35…”

“…In general, it is a regenerable, reusable, and easy-to-handle solid material that can be used for the synthesis of tertiary iodides, ethers, and esters; it can also be utilized in the transesterification of triglycerides to produce biodiesel, all of which we have reported earlier in our “proof-of-concept” paper. 33 Furthermore, we have evaluated the dried Dowex H + /NaX (X = Br, I) approach more systematically for its ability to achieve ring openings of cyclic ethers to produce useful building blocks; 34 more recently, we have reported a green and efficient esterification method based on the catalysis with the dried Dowex H + /NaI method 35 (Scheme 1).…”

Transition Metal-Based Nanoparticles Catalyzed Esterification Reactions

“…Leopold Gmelin, a German chemist was the first person to coin the term "ester". [1][2][3][4] In addition to good smelling substances, ester groups are widely found in biodegradable polymers like polylactic acid, thermoplastics like polyethylene terephthalate, analgesics. Numerous industrially important products like plasticizers, coatings, perfumes, and resins consist of ester groups.…”