Synthesis of amides from esters and amines under microwave irradiation

Article abstract of DOI:10.1081/SCC-120014792

Formamide, primary and secondary amines react with esters in the presence of potassium tert-butoxide under microwave irradiation. Substituted amides are formed in yields (generally more than 70%) much higher than under conventional heating.

Full text of DOI:10.1081/SCC-120014792

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SYNTHESIS OF AMIDES FROM ESTERS AND AMINES
UNDER MICROWAVE IRRADIATION
Fatima-Zohra Zradni a , Jack Hamelin b & Aicha Derdour a
a Faculté des Sciences, Laboratoire de Synthèse Organique, Es-sénia, Oran Algerie, BP 1524
b Laboratoire de Synthèse et Electrosynthèse Organiques 3, Université de Rennes I et CNRS,
UMR 6510, Avenue du Général Leclerc.F-35042, Rennes I, France
Version of record first published: 22 May 2009.
To cite this article: Fatima-Zohra Zradni , Jack Hamelin & Aicha Derdour (2002): SYNTHESIS OF AMIDES FROM ESTERS AND
AMINES UNDER MICROWAVE IRRADIATION, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 32:22, 3525-3531
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SYNTHETIC COMMUNICATIONS
Vol. 32, No. 22, pp. 3525–3531, 2002
SYNTHESIS OF AMIDES FROM
ESTERS AND AMINES UNDER
MICROWAVE IRRADIATION
Fatima-Zohra Zradni,1 Jack Hamelin,2,
*
and Aicha Derdour1
1Faculte des Sciences, Laboratoire de Synthese
Organique, BP 1524 Es-senia, Oran Algerie
2Laboratoire de Synthese et Electrosynthese
Organiques 3, Universite de Rennes I et CNRS,
UMR 6510, Avenue du General Leclerc.F-35042
Rennes I, France
ABSTRACT
Formamide, primary and secondary amines react with esters in
the presence of potassium tert-butoxide under microwave irra-
diation. Substituted amides are formed in yields (generally
more than 70%) much higher than under conventional heating.
The amide bond is an important building unit naturally or syntheti-
cally occurring.[1,2] It is present as a key in many important natural products
and man-made compounds.[2] For example, N-acylalkylenediamines[3] react
with 4-amino-2-chloro-6,7-dimethoxyquinazolines to give a variety of
antihypertensive agents.[4]
*Corresponding author. E-mail: jack.hamelin@univ-rennes1.fr
3525
DOI: 10.1081/SCC-120014792
Copyright & 2002 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

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3526
ZRADNI, HAMELIN, AND DERDOUR
The synthesis of amides from carboxylic esters is a transformation
of general synthetic interest which in many cases needs harsh conditions
(temperature, reaction periods) or the use of strong catalysts.[5,6]
However, the enormous growth in the use of microwave irradiation
this last decade in synthetic organic chemistry[7] inspired us to study this
reaction. A recently described synthesis of N-acylalkylenediamines from the
corresponding carboxylic esters and alkylene diamines which requires
prolonged reaction times (3–16 h)[8] and also synthesis of N-arylamides,[9]
prompt us to report our results under solvent-free conditions which proceed
in a much shorter time (2–3 min).
For the synthesis of primary amides, the reactions were carried out
using an ester (1 eq.), formamide (3 eq.) and solid potassium tert-butoxide
(t-BuOK) (1 eq.) and the reaction mixture was submitted to microwave
irradiation (MWI) in a focused microwave oven (Synthewave 402Õ).[10]
MWI=t-BuOK
R1CO2R2 þ HCONH3 ÀÀÀÀÀÀÀ! R1CONH2 þ HCO2R2
R1¼Me, C6H5CH2, NCCH2, C6H5CH¼CH, H3CCO2CH2;
R2¼Me, Et
While the synthesis of secondary amides are realized from esters (1 eq.)
and butylamine (1 eq.), tertiary amides result from esters (1 eq.) and
secondary amines (1 eq.) with adjusted amounts of (t-BuOK) as shown in
Table 2 for the following reactions.
MWI=t-BuOK
R1CO2R2 þ BuNH2 ÀÀÀÀÀÀÀ! R1CONHBu
MWI=t-BuOK
R1CO2R2 þ R3R4NH ÀÀÀÀÀÀÀ! R1CONR3R4
Table 1. Solvent-Free Synthesis of Amides from Esters and Formamide Using
Potassium tert-Butoxide
Time
(min)
Yielda
(%)
Entry
Starting Materials
Products
CH3CONH2
C6H5CH2CONH2
NCCH2CONH2
1
2
3
4
5
CH3CO2C2H5
2
3
2
2
3
80
79
72
85
43
C6H5CH2CO2CH3
NCCH2CO2CH3
C6H5CH¼CHCO2CH3
CH2(CO2CH3)2
C6H5CH¼CHCONH2
CH3CO2CH2CONH2
aThe yield refers to isolated products which exhibit physical and spectral properties
(NMR spectra) in agreement with the assigned structures.

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SYNTHESIS OF AMIDES FROM ESTERS AND AMINES
3527