Base-promoted direct amidation of esters: beyond the current scope and practical applications

Abstract

A new method for direct amidation of unactivated esters with unprecedented substrate scope is developed.

Potassium t‐Butoxide‐Promoted Metal‐Free Synthesis of Pyrazino[1,2‐a]indoles via Direct Amidation and Intramolecular Hydroamination Reaction

“…The DMSO/t-BuOK system was reported as a superbase. [16] To our delight, the reaction occured considerably in 5 minutes at room temperature. Thus, subsequent experiments measuring the amount of ester, amine, and base were conducted at this temperature.…”

“…used microwave irradiation for direct amidation of esters (Scheme 2.c), [15] and Slavchev et al . achieved synthesis of amides from base‐promoted direct amidation shown in Scheme 2.d [16] …”

Recent Advances in Carbon‐Nitrogen/Carbon‐Oxygen Bond Formation Under Transition‐Metal‐Free Conditions

“…Finally, additional control experiments and DFT calculation results indicated a 1,3‐chelation of sodium ions with oxygen atoms from esters, while activation of amines by NaO t Bu were included in this process. Besides, KO t Bu‐promoted amidation of esters were reported by other researchers, including ball milling strategy, [90] mechanistic study [91] and phosphoramidates synthesis by direct amidation of triethylphosphate [92] …”

“…[55] A combination of a seleno-containing urea catalyst (64) and 34 * [O] was used as the catalytic system, while molecular oxygen (O 2 ) was utilized as a terminal oxidant and PhSiH 3 as a terminal reductant (Scheme 17b). With regard to the proposed catalytic cycle, the carboxylic acid ( 91) was firstly converted into the corresponding selenoester (Int-11) in situ from a diselenide catalyst (Catalyst-Se) 2 (64), which was then attacked by the amine substrate (92). Except in solution-phase peptide synthesis, this catalytic system was also applicable in solidphase peptide synthesis (SPPS).…”

“…Besides, KOtBu- promoted amidation of esters were reported by other researchers, including ball milling strategy, [90] mechanistic study [91] and phosphoramidates synthesis by direct amidation of triethylphosphate. [92]…”