Microwave-assisted N-alkylation of potassium phthalimide and potassium succinimide onto silica gel in dry media

Article abstract of DOI:10.1080/10426500490466157

Synthesis of N-alkyl phthalimides and N-alkyl succinimides through alkylation of potassium phthalimide and potassium succinimide in dry media catalyzed by phase-transfer catalyst under microwave irradiation will be reported. The reactions were with fairly high yield.

Full text of DOI:10.1080/10426500490466157

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Phosphorus, Sulfur, and Silicon and the Related
Elements
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MICROWAVE-ASSISTED N-ALKYLATION OF POTASSIUM
PHTHALIMIDE AND POTASSIUM SUCCINIMIDE ONTO
SILICA GEL IN DRY MEDIA
a
a
a
a
R. Hekmatshoar , M. M. Heravi , B. Baghernejad & K. Asadolah
a
Department of Chemistry, School of Science, Alzahra University, Vanak, Tehran, Iran
Version of record first published: 16 Aug 2010.
To cite this article: R. Hekmatshoar , M. M. Heravi , B. Baghernejad & K. Asadolah (2004): MICROWAVE-ASSISTED N-
ALKYLATION OF POTASSIUM PHTHALIMIDE AND POTASSIUM SUCCINIMIDE ONTO SILICA GEL IN DRY MEDIA, Phosphorus, Sulfur, and
Silicon and the Related Elements, 179:8, 1611-1614
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Phosphorus, Sulfur, and Silicon, 179:1611–1614, 2004
Copyright ꢀC Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490466157
MICROWAVE-ASSISTED N-ALKYLATION
OF POTASSIUM PHTHALIMIDE AND POTASSIUM
SUCCINIMIDE ONTO SILICA GEL IN DRY MEDIA
R. Hekmatshoar, M. M. Heravi, B. Baghernejad,
and K. Asadolah
Department of Chemistry, School of Science, Alzahra University,
Vanak, Tehran, Iran
(
Received September 2, 2003; accepted December 9, 2003)
Synthesis of N-alkyl phthalimides and N-alkyl succinimides through
alkylation of potassium phthalimide and potassium succinimide in dry
media catalyzed by phase-transfer catalyst under microwave irradia-
tion will be reported. The reactions were with fairly high yield.
Keywords: Microwave; potassium phthalimide; potassium succin-
imide; TBAB
INTRODUCTION
In the past few years there has been interest in the use of microwave
1
heating in organic synthesis. The use of such nonconventional reaction
conditions reveals features such as the following: a short reaction time
compared to conventional heating, ease of workup after the reaction,
2
reduction in the usual thermal degradation, better selectivity, and re-
action under dry conditions (i.e., in the absence of a solvent on a solid
support with or without catalysts), all of which were originally devel-
3
oped in the late 1980s. Synthesis without solvents under microwave
4
irradiation offers several advantages. The absence of solvent reduces
the risk of explosions when the reaction takes place in a closed vessel
in an oven.
Moreover, aprotic dipolar solvents with high boiling points are ex-
pensive and difficult to remove from the reaction mixtures. During
microwave induction of reactions under dry conditions, the reactants
adsorbed on the surface of alumina, silica gel, clay, and others absorb
Address correspondence to R. Hekmatshoar, Department of Chemistry, School of
Science, Alzahra University, Vanak, Tehran, Iran. E-mail: rhekmatus@yahoo.com
1
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612
R. Hekmatshoar et al.
the microwaves, whereas the support does not, nor does it restrict the
transmission of microwaves. Consequently, such supported reagents ef-
ficiently induce reactions under safe and simple conditions with do-
mestic microwave ovens instead of specialized expensive commercial
microwave systems.
The Gabriel synthesis for converting halides to primary amines is
based on the reaction of halide with potassium phthalimide. The reac-
tion is usually rather slow but can be conventionally speeded by the use
of an aprotic solvent such as DMF.
In this article we report the remarkably fast synthesis method of
N-alkyl phthalimide and N-alkyl succinimide via alkylation of potas-
sium phthalimide and potassium succinimide in dry media under mi-
crowave irradiation (Scheme 1).
SCHEME 1
RESULTS AND DISCUSSION
The reactions were carried out by simply mixing of potassium phthalim-
ide or potassium succinimide with an excess of alkyl halide, a catalytic
amount of tetrabutyl ammonium bromide (TBAB), and silica gel pow-
der in CH2Cl2 with stirring. The solvent was evaporated and then the
mixture irradiated in an open vessel in a domestic microwave oven for
the indicated time in Table I.
Superheating of liquids is common under microwave irradiation,
thus the strategy of reaction is to keep the reaction temperature
substantially below the boiling point of each compound used for the

N-Alkyl Phthalimides
1613
TABLE I Phthalimide and Succinimide Derivatives Synthesis by TBAB
Catalyst and Alkyl Bromide Under Microwave Irradiation
◦
m.p. ( C) or
◦
b.p. ( C)/mm Hg
Time Yield Found
Product
RX
(min) (%) (Bielstin)
Reported
N-benzyl phthalimide
N-propargyl phthalimide Propargyl bromide
Benzyl bromide
3
4
4
4
4
3
4
4
4
4
98
91
89
76
68
88
53
75
72
60
116
66
71
114
67
70
77
135
103
N-allyl phthalimide
N-ethyl phthalimide
N-methyl phthalimide
N-benzyl succinimide
N-methyl succinimide
N-propargyl succinimide Propargyl bromide
N-allyl succinimide
N-ethyl succinimide
Allyl bromide
Ethyl bromide
Methyl bromide
Benzyl bromide
Methyl bromide
79
134
103
71
240
243
236
64.5
237/760 mm Hg
241/760 mm Hg
232/760 mm Hg
Allyl bromide
Ethyl bromide
reaction. One of the best solutions is to repeat an experiment several
times, increasing the power slowly so that vapors do not escape.
EXPERIMENTAL
Melting points were measured with an electrothermal 9100 apparatus
and are uncorrected. Infrared (IR) spectra were recorded on a Philips
1
13
PU 9800 fourier transform infrared (FTIR) instrument. H and
C
NMR spectra were recorded on a JEOL EX-90A spectrometer at 90
and 22.6 MHz. All products are known compounds; their physical and
spectroscopic data were compared with those of authentic samples and
were found to be identical. Mass spectra were recorded on a Finnigan-
MaH8430 mass spectrometer operating at an ionization potential 70 eV.
GENERAL PROCEDURE
Potassium phthalimide (20 mmol) was powdered in a mortar and thor-
oughly mixed with TBAB (0.5 mmol) and silica gel powder (1 g). Alkyl
halide was added dropwise, and then 5 ml of CH2Cl2 was added. The
mixture was stirred, the solvent evaporated, and then the mixture
placed in a microwave oven and irradiated for the time indicated in
Table I. The product was extracted by methylene chloride, the solvent
removed, and the crude product recrystallized from ethanol to afford
the pure product.

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R. Hekmatshoar et al.
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