Journal of the Chinese Chemical Society, 2008, 55, 659-662
659
A Novel and Efficient Catalyst to One-pot Synthesis of
2-Amino-4H-chromenes by Methanesulfonic Acid
Majid M. Heravi,* Bita Baghernejad and Hossein A. Oskooie
Department of Chemistry, School of Science, Azzahra University, Vanak, Tehran, Iran
Methanesulfonic acid efficiently catalyzes the one-pot, three component reaction of an aromatic alde-
hyde, malonitrile and a or b-naphthol to yield 2-amino-4H-chromenes in very good yields.
Keywords: Methanesulfonic acid; 2-Amino-4H-chromenes; One-pot.
INTRODUCTION
2-Amino-4H-chromenes and their derivatives are of
tion of 1,4-dihydropyridines.11 MSA is a strong acid (pKa =
-1.9), which is almost completely ionized at 0.1 M in an
aqueous solution and has a low tendency to oxidize organic
compounds. It is, however, far less corrosive and toxic than
other mineral acids. Under normal conditions, aqueous so-
lutions evolve no dangerous volatiles, making it safe to
handle. Finally, it is readily biodegradable within 28 days,
only forming CO2 and sulfate, making them an environ-
mentally benign material.12 Furthermore, it has the advan-
tage, as will be shown, that it can be separated readily from
the reaction mixture and reused.
considerable interest as they possess a wide range of bio-
logical properties,1 such as spasmolytic, diuretic, anticoag-
ulant, anticancer and antianaphylactic activity.2 In addi-
tion, they can be used as cognitive enhancers for the treat-
ment of neurodegenerative diseases, including Alzheimer’s
disease, amyotrophic lateral sclerosis, Huntington’s dis-
ease, Parkinson’s disease, AIDS associated dementia and
Down’s syndrome as well as for the treatment of schizo-
phrenia and myoclonus.3
The increasing attention during recent decades for
environmental protection has led modern academic and in-
dustrial groups to develop chemical processes with maxi-
mum yield and minimum cost whilst using nontoxic re-
agents, solvents and catalysts. One of the tools used to com-
bine economic aspects with the environmental ones is the
multicomponent reaction (MCR) strategy; this process
consists of two or more synthetic steps which are carried
out without isolation of any intermediate, thus reducing
time and saving money, energy and raw materials.4
As part of our program aimed at developing new se-
lective and environmentally friendly methodologies for
the preparation of fine chemicals,13 herein we report the
synthesis of 2-amino-4H-chromenes using MSA in good
yields.
RESULTS AND DISCUSSION
2-Amino-chromenes are generally prepared by re-
fluxing malononitrile, aldehyde and activated phenol in the
presence of hazardous organic bases like piperidine for
several hours.14 A literature survey revealed that several
modified procedures using CTACl,15 TEBA,16 and g alu-
mina17 as catalysts have been recently reported but all these
methods require long refluxing hours. Based on previous
studies to develop new and heterogeneous catalyst systems
for fine chemical preparation,13 we have studied the three-
component synthesis of 2-amino-4H-chromenes via one-
pot reaction of aldehydes, malonitrile and a- or b-naphthol
using methanesulfonic acid as an available, green and inex-
pensive catalyst (Scheme I) in good yields (Table 1).
The scope and the generality of the present method
We performed the synthesis of 2-amino-4H-chromenes
through a three-component reaction employing methane-
sulfonic acid as a catalyst. Methanesulfonic acid, CH3SO3H
(MSA) is an alkanesulfonic acid, which has numerous ap-
plications, for example, as an esterification or alkylation
catalyst, as a polymer solvent, in the electroplating and
electrochemistry industry, etc. MSA also is an effective re-
agent for the conversion of alcohols into corresponding
amides,5 Fries-rearrangement,6 Beckmann rearrangement,7
hydration of nitriles into amides,8 monoesterification of
diols,9 N-nitrosation of secondary amines,10 and aromatiza-
* Corresponding author. Tel: +982188041344; Fax: +982188047861; E-mail: mmh1331@yahoo.com (M. M. Heravi)