Copper-Catalyzed Methyl Esterification Reactions via C–C Bond Cleavage

Abstract

The highly effective synthesis of methyl esters from benzylic alcohols, aldehydes, or acids via copper-catalyzed C-C cleavage from tert-butyl hydroperoxide is reported in this paper for the first time. Our protocol is easily accessible and practical, making it a possible supplement for the traditional way.

TBHP as Methyl Source under Metal‐Free Aerobic Conditions To Synthesize Quinazolin‐4(3H)‐ones and Quinazolines by Oxidative Amination of C(sp3)–H Bond

“…Results of the optimization study for the transformation of 2-aminobenzamide 1e into quinazolin-4(3H)-one 3e. [ to the literature, [6][7][8][9] suggests that the presence of a metal catalyst was not essential for TBHP to act as a methyl source. To exclude DMF as the carbon source, we next assessed acetonitrile as the solvent under identical conditions, which led to the isolation of 3e in 38 % yield (Table 1, Entry 3).…”

“…tert ‐Butyl hydroperoxide, which has been widely used as an oxidant, has also been employed as a source of a methyl radical in the presence of a copper catalyst. Mao et al first disclosed the effective synthesis of methyl esters by using either benzylic alcohols, aldehydes, or acids in the copper‐catalyzed C–C bond cleavage of TBHP (Figure ) . Subsequently, Li et al developed a copper‐catalyzed synthesis of methyl esters from aromatic aldehydes and benzylic alcohols in the presence of TBHP .…”

“…Mao et al first disclosed the effective synthesis of methyl esters by using either benzylic alcohols, aldehydes, or acids in the copper-catalyzed C-C bond cleavage of TBHP ( Figure 2). [6] Subsequently, Li et al developed a copper-catalyzed synthesis of methyl esters from aromatic aldehydes and benzylic alcohols in the presence of TBHP. [7] ones and quinazolines from 2-aminobenzamides and 2-carbonyl-substituted anilines, respectively.…”

Copper‐Catalyzed Double Intramolecular Ullmann Coupling for the Synthesis of Diastereomerically and Enantiomerically Pure 4b,9b‐Dihydrobenzofuro[3,2‐b]benzofurans

“…Since the 8‐hydroxyquinoline ligand can easily be exchanged for other ligands,19b these complexes, which are usually prepared in situ, are potential catalysts. In addition to the already mentioned O ‐arylations, a variety of other reactions, including C ‐vinylations of arylboronic acids,19c N ‐arylations of pyridine‐2(1 H )‐ones,19d pyridazones19e and imidazoles,19f and the synthesis of methyl benzoates from benzyl alcohol and tert ‐butyl hydroperoxide,19g can be catalyzed by Cu II oxinate or by using a copper source in the presence of 8‐hydroxyquinoline as a ligand. With Cu II oxinate (10 mol‐%) and K 3 PO 4 (4 equiv.)…”

Facile Coupling of Aldehydes with Alcohols: An Evolved Tishchenko Process for the Preparation of Unsymmetrical Esters

“…If our proposed scenario is operative, the present esterification process can be viewed as an evolved Tishchenko reaction, as both processes have a similar metal alkoxide as the active species. Compared with other esterification strategies between aldehydes and alcohols, such as oxidative esterification and dehydrogenative esterification, no external strong oxidants are necessary in this approach, which provides an advanced method towards the synthesis of unsymmetrical esters under mild conditions …”