Bu₄NI‐Catalyzed and tBuOOH‐Oxidized Esterification of Aldehydes with Alkyl Halides in Water

Abstract

The importance of esters has stimulated significant efforts to develop efficient methods for their synthesis. In this study,a no xidative esterification of aldehydes with alkyl halidesb yu sing tert-butyl hydroperoxidea sa n oxidant, Bu 4 NI as catalyst, andw ater as solvent is presented. Notably,t his novel esterification protocol is suitable for both aromatic and aliphatic aldehydes, primary and secondary alkyl halides to give ester products with broad structural diversity. Through an intramolecular version of this novel esterification process, an alternative synthetic approach toward the biologically interesting isobenzofuran-1(3 H)-one was also realized. Compared with literature procedures, the synthetic strategies developed herein showed advantages such as direct use of commercially available and economical starting materials,w ide substrate scope, good tolerance of functional groups, sustainable oxidant, and no need of an inert atmosphere or dry solvents.

A Straightforward Conversion of Activated Amides and Haloalkanes into Esters under Transition-Metal-Free Cs2CO3/DMAP Conditions

“…Cyclohexanecarbonyl saccharin (1p). 2 Following general procedure, 1p was isolated as a white solid (2.57 g, 89%); 1 H NMR (400 MHz, CDCl3) δ 8.14 (d, J = 7.6 Hz, 1H), 8.00 -7.94 (m, 2H), 7.93 -7.88 (m, 1H), 3.39 (tt, 1H), 1.98 (d, J = 12.4 Hz, 2H), 1.88 -1.81 (m, 2H), 1.72 (d, J = 12.3 Hz, 1H), 1.58 (qd, J = 12.3, 2.7 Hz, 2H), 1.43 -1.33 (m, 2H), 1.31 -1.24 (m, 1H).Detail descriptions for productsButyl benzoate (3aa) 4. Following general procedure, 3aa was isolated as a colorless oil (45.9 mg, 86%);1 H NMR (400 MHz, CDCl3) δ 8.05 (d, J = 7.2 Hz, 2H), 7.58 -7.51 (m, 1H), 7.47 -7.40 (m, 2H), 4.33 (t, J = 6.6 Hz, 2H), 1.79 -1.71 (m, 2H), 1.53 -1.43 (m, 2H), 0.98 (t, J = 7.4 Hz, 3H).…”

“…fluorobenzoate (3ga) 4. Following general procedure, 3ga was isolated as a colorless oil (52.9 mg, 90%);1 H NMR (400 MHz, CDCl3) δ 8.09 -8.03 (m, 2H), 7.15 -7.05 (m, 2H), 4.32 (t, J = 6.6 Hz, 2H), 1.80 -1.70 (m, 2H), 1.53 -1.42 (m, 2H), 0.98 (t, J = 7.4 Hz, 3H); 19 F NMR (376 MHz, CDCl3) δ -106.10.…”

Copper Catalyzed‐TBHP/DTBP Promoted C(sp2)−H Bond Scission of Aldehydes: An Approach to Transform Aldehyde to Esters

“…Notably, unactivated aldehydes such as 3‐phenylpropanal and cyclohexane carboxaldehyde reacted well with primary aliphatic bromides, delivering the corresponding esters 3 u and 3 v in good yields. It is worth mentioning that a combination of TBHP and the tetrabutylammonium iodide (TBAI) has also been reported for the oxidative esterification of aldehydes with alkyl bromides [16] . However, when they performed the reaction in the presence of benzyl bromide derivatives, the inferior yield of the corresponding ester was obtained [16] .…”

The Chemistry of Peresters

“…A nearly identical transformation may be performed on benzyl halides (bromides) where again the perester is generated in‐situ . This example demonstrates that organic soluble iodide can be used as a promoter and is shown in Figure .…”