2-Iodoxybenzoic Acid/Tetraethylammonium Bromide/Water: An Efficient Combination for Oxidative Cleavage of Acetals

Abstract

o -I o d o x y b e n z o i c A c i d / T e t r a e t h y l a m m o n i u m B r o m i d e / W a t e r C o m b i n a t i o nAbstract: A simple and efficient procedure has been developed for the oxidation of cyclic and acyclic acetals to the corresponding hydroxyalkyl carboxylic esters and simple esters, respectively. 2-Iodoxybenzoic acid (IBX) in the presence of tetraethylammonium bromide was employed for the reaction in aqueous media. The salient features of the protocol include short reaction time, environmentally benign reagents and solvent, and moderate to high yields.

Facile oxidative hydrolysis of acetals to esters using hypervalent iodine(III)/LiBr combination in water

“…Our previous study prompted us to initially carry out the reaction in water. 20 In the absence of additive and despite prolonged reaction time (3 h), no reaction took place and mostly 1a was recovered (entry 1). The addition of bromide salts such as KBr, NaBr, LiBr, and Et 4 NBr promoted the reaction to afford 2a in moderate to excellent conversion (entries 2-5); LiBr gave the best conversion (91%).…”

“…It is worth noting that the oxidative hydrolysis of 1b and 1d under our previously established conditions (IBX (1.1 equiv)/Et 4 NBr (0.5 equiv)/H 2 O/65 C) gave inferior results; 2b was isolated in 50% yield after 3 h and no reaction in case of 1d. 20 Oxidation of cyclic acetals derived from bromo-, chloro-, fluoro-, and methyl-substituted aromatic dioxolanes and dioxanes gave the corresponding esters in moderate to excellent yields (entries 5-12). Furthermore, cyclic acetals derived from aliphatic aldehydes generally afforded the corresponding esters in good yields (entries [13][14][15][16][17][18][19][20][21][22].…”

“…20 Oxidation of cyclic acetals derived from bromo-, chloro-, fluoro-, and methyl-substituted aromatic dioxolanes and dioxanes gave the corresponding esters in moderate to excellent yields (entries 5-12). Furthermore, cyclic acetals derived from aliphatic aldehydes generally afforded the corresponding esters in good yields (entries [13][14][15][16][17][18][19][20][21][22]. High yields were also obtained with the cyclic acetals derived from a-disubstituted aldehydes (entries [23][24][25][26].…”

“…18 In continuation of our ongoing research interest regarding the development of new synthetic applications of o-iodoxybenzoic acid (IBX), 19 we have recently disclosed a combined use of IBX and tetraethylammonium bromide in water for oxidative cleavage of acetals to their corresponding hydroxyalkyl esters and simple esters. 20 Encouraged by these results, we now report a practical and facile oxidative hydrolysis of cyclic acetals by (diacetoxy)iodobenzene (PhI(OAc) 2 , DIB) in the presence of lithium bromide (LiBr) in water at room temperature to afford the corresponding hydroxyalkyl carboxylic esters (Scheme 1 …”

Facile and efficient synthesis of hydroxyalkyl esters from cyclic acetals through aerobic photo-oxidation using anthraquinone-2-carboxylic acid

“…3 Metal reagents used for direct oxidative cleavage of 1,3-dioxolanes include molecular oxygen-Co(II), 4 potassium permanganate, 5 and tert-butylhydroperoxide in the presence of transition metals. 6 In addition, many methods that employ nonmetal reagents such as ozone, 7 hypochlorous acid, 8 N-hydroxyphthalimide in electrochemical oxidation, 9 tert-butylhydroperoxide-iodine(III) compounds, 10 IBX/Et 4 NBr, 11 (diacetoxy)iodobenzene/LiBr, 12 di-tert-butyl peroxide, 13 electrophilic halogen, 14 and m-chloroperbenzoic acid in the presence of 2,2 0 -bipyridinium chlorochromate or boron trifluoride-diethyl ether, 15 sodium perborate in acetic anhydride, 16 and oxone 17 have been reported.…”