The Effect of Indium(III) Triflate in Oxone-Mediated Oxidative Methyl Esterification of Aldehydes

Abstract

An oxidative methyl esterification of aldehydes was effectively achieved. The trivalent indium reagent, indium(III) triflate, was revealed to accelerate the reactions in many cases. Aromatic aldehydes with various substituents were subjected to this method, and each produced the corresponding methyl esters in good to excellent yields within a relatively short reaction time.

Cobalt(II)/TFA‐Catalyzed Oxidative Esterification of Aldehydes and Alcohols: Dual Role of the Acid Co‐Catalyst

“…Having selected TFAa st he optimal additive fort his transformation, we turned our attention to optimizing various other reactionc onditions ( Table 2). We found that the reactionc onversion was improved by 12 %a te levated temperature without al oss of selectivity ( [8][9][10][11][12][13][14]. Under optimized conditions, unsubstituted benzaldehyde( 1a) smoothly coupled with MeOH (2a)t og enerate methyl carbox- [b] 0.26 T-HYDRO CoCl 2 70 58 12 14 [c] 0.26 T-HYDRO CoCl 2 ylate 3aa in ag ood yield of 83 %( Ta ble 2, entry 12).…”

“…Next, ar ange of aldehydes( 1)w ere examined in the reaction with MeOH (2a)u nder our optimized conditions ( Table 3, entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. We found that electronic effects owing to substituents at the meta or para positions of the aldehyde had an egligible influence on the reactione fficiency (Table3,e ntries [2][3][4][5][6][7][8][9][10][11][12]. The methyl carboxylate products of aldehyde substrates that were substitutedw ith halide,n itro, or methoxy groups were all obtainedi ns atisfactory yields.…”

“…However,s everal challenges still remain.T ypically,t he relativelyw eak CÀHb ond in the formyl group of aldehydes is sensitive to electron-transfer reagents and undesired decarboxylation [6] or peroxidation reactions [7] often occurb eyond the dehydrogenative CÀOc ross-coupling reaction. To address this problem, strategies for the pre-activation of carbonyl groups by using variousc atalysts or additives, such as carbenes [8] and suitable acids (Scheme 1a), [9] have been extensively investigated. Notably,W ur eported an efficient zinc-catalyzed oxidative esterification reactiono fb enzyl alcohols by using CF 3 COOH (TFA) as ac o-catalyst, although ac atalytic amount of pyridine-2,6-dicarboxylic acida saligand and an excess of the alkoxy reagent (MeOH)w eres tillr equired.…”

Chloramine-T-Mediated Oxidation of Benzylic Alcohols Using Indium(III) Triflate

“…On the other hand, we have reported useful methodologies focused on indium(III) triflate using solvents such as CH 2 Cl 2 , THF, or MeOH, and thus these outcomes in terms of solvents need not to deny the compatibility of Lewis acids and solvents. [19][20][21] The use of a 0.3 eq of indium(III) triflate was discovered to be one of the key factors for the optimal reaction condition (entries 1, 7, 8, and 9). The reaction without Lewis acid gave a yield of 37% (entry 9), and thus the presence of indium(III) triflate must contribute for smooth reactions based on the previously suggested reaction mechanism in a similar manner.…”

Highly-Efficient Conversion of Primary Amides to Nitriles Using Indium(III) Triflate as the Catalyst

“…Another rare metal, In, as trivalent InCl 3 , has been used to accelerate the dehydration of oximes and arenes with benzyl alcohols [31], [32]. After studying the chemical utility of trivalent indium reagents [33]- [36], we conducted a preliminary investigation into the use of trivalent indium reagents for the conversion of primary amides. As part of our ongoing investigations, In(OTf) 3 was found to be a suitable and highly-efficient catalyst for transforming primary amides to nitriles in combination with N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) [26]- [30], which has unique dehydrating properties as described in recent reports (Figure 1).…”