M.SELVA

P. TUNDO

Archivio Ricerca Ca'Foscari

TETRAHEDRON
LETTERS
Tetrahedron Letters 44 (2003) 8139–8142Pergamon
Selective N-methylation of primary aliphatic amines with
dimethyl carbonate in the presence of alkali cation exchanged
Y-faujasites
Maurizio Selva* and Pietro Tundo
Dipartimento di Scienze Ambientali dell’Universita` Ca’ Foscari, Calle Larga S. Marta 2137, 30123 Venezia, Italy
Received 17 July 2003; revised 18 August 2003; accepted 3 September 2003
Abstract—The N-methylation of aliphatic amines [XC6H4(CH2)nNH2; n=1, X=H (1a), o-MeO (1b), p-MeO (1c); n=2, X=H
(2a), o-MeO (2b); 1d: PhCH(Me)NH2] with dimethyl carbonate (DMC) is efficiently catalysed by NaY faujasite: on condition that
CO2 (a co-product of the reaction) is carefully removed, N-methyl- and N,N-dimethyl-amines (RNHMe and RNMe2) are
obtained in good overall yields (70–90%). Otherwise, in the presence of CO2, carbamates (RNHCO2Me) form competitively to a
large extent. The reaction probably proceeds through a BAl2 displacement of the amine on DMC.
© 2003 Elsevier Ltd. All rights reserved.
In the presence of alkali cation exchanged Y-faujasites
(e.g. NaY and KY), the reaction of dimethyl carbonate
with primary aromatic amines affords the correspond-
ing mono-N-methyl derivatives with unprecedented
selectivity (92–99%). This holds even for anilines deacti-
vated by both electronic and steric effects (Scheme 1).1
Besides the synthetic outcome, this reaction shows rele-
vant environmentally benign features: it uses a non-
toxic methylating agent (DMC) coupled with eco-safe
solids (zeolites) as catalysts, it does not require addi-
tional solvents, and neither organic nor inorganic by-
products are formed.2
As a part of our research program on the reactivity of
DMC over Y zeolites, we were interested in the N-
methylation of primary aliphatic amines as well. The
higher nucleophilicity of these substrates posed a severe
limitation to the reaction selectivity, due not only to
the double N-methylation but primarily, to the forma-
tion of carbamates (Scheme 2).1a,c Apparently,
BAc2 and BAl2 mechanisms, i.e. the attack of the amine
to the carbonyl (BAc2) and to the methyl (BAl2)
groups of DMC, were possible without any discrimina-
tion.
In this paper, we wish to report a further investigation
on this reaction which discloses the synthetic potential
for the preparation of N-methyl amines and some
relevant features of the methylation/methoxycarbonyla-
tion mechanisms of aliphatic amines with DMC.
Initially, benzylamine 1a, o- and p-methoxybenzyl-
amine, and (-methyl)benzylamine (compounds 1b, 1c,
and 1d respectively) were chosen as substrates (Table
1). In a typical procedure (entry 7), a three-necked,
jacketed, 25 mL round-bottomed flask fitted with a
N2-bubbler, an adapter for the withdrawal of samples,
a reflux condenser connected to a gas flowmeter, and a
magnetic bar, was loaded with a solution of benzyl-
amine (1a, 0.3 g, 2.8 mmol) in dimethyl carbonate (20
mL), and NaY (0.9 g). The flask was heated at the
reflux temperature of DMC (90°C), while the mixture
was vigorously stirred. A N2 flow of 25 mL/min was
Scheme 1. Mono-N-methylation of anilines with DMC.
* Corresponding author. Tel.: +39 041 234 8687; fax: +39 041 234 8620; e-mail: selva@unive.it
0040-4039/$ - see front matter © 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2003.09.016
M. Sela, P. Tundo / Tetrahedron Letters 44 (2003) 8139–81428140
Scheme 2. R=CH2Ph, Cy.
ucts C and MC, Scheme 2) and the oxidative deamina-
tion (product E: XC6H4CH2N=CHPh) of the amine 1a
take place to a large extent.4 The Bro¨nsted acidic zeolite
(HY) is even more unsatisfactory (entry 6): at a 30%
conversion, SMet is only 33%. We suggest that a strong
acid-base interaction may hold amine within the cata-
lyst pores,5 so that any advantage due to the smaller
size of the cation is cancelled.
Much better results can be gathered for the N-methyla-
tion of compound 1a as well as of 1b–d, when reactions
are performed over NaY—a commercially available
faujasite—in the presence of a N2 stream (entries 7–10):
SMet of 91–100% are attained at conversions of 70–94%.
This improvement arises not only from the increase
of the methylation versus carbamation selectivity
(SMet/Carb), but also from a fall in formation of the
side-product E.
The same procedure is profitable also for the reaction
of phenethylamine (2a) and its o-methoxyderivative [2b:
o-MeOC6H4(CH2)2NH2] with DMC. The presence of a
N2 flow is an extremely simple and efficient method to
allow an excellent N-methylation selectivity (91–98%)
for compounds 2a–b, while the carbamation reaction is
practically ruled out.
The data in Table 1 give a clear indication of the major
role played by the CO2 which, as is shown in Scheme 1,
bubbled into the mixture and mantained throughout
the reaction. At intervals, samples (0.1 mL) were with-
drawn and were analyzed by both GC and GC/MS.
The structures of the products were also confirmed by
comparison with authentic samples of N-methylbenzyl-
amine, N,N-dimethylbenzylamine, methyl N-benzyl
carbamate, and methyl N-benzyl, N-methyl carbamate.
The same reaction was also performed under a static
N2-atmosphere (entries 1–6).
According to our previous experiments,1c without the
N2-bubbling, the increase of Lewis acidity of the cata-
lyst (going from CsY to LiY faujasites)3 shows a posi-
tive effect on the reaction rate (compare entries 1–2 and
5).
However, at higher conversions (89 and 97%: entries
3–4), the selectivity (SMet) towards the N-methylation
reaction is clearly variable (43 and 64%, respectively).
Competitive side reactions, i.e. the carbamation (prod-
Table 1. N-Methylation of amines 1a–d and 2a–b with DMC over MY zeolites
SMet/Carb
b (%)Products (%)a SMet
c (%)
MY T (°C)AmineEntry t (h) N2 flow D C MC EMConv. (%)
1a LiY 90 7 No 43 34 91
31a NaY 90 7 No 40 30 72
6474121374983 89No5690NaY1a
27 12 49 43NaY 1104d 231a No 97 - 42 16
5 721081836No2290CsY1a
5512846 3330No2390HY1a6
1a 1 98 96NaY 90 48 Yes 94 20 70 37
1b NaY 90 23 Yes 708 30 34 5 1 91 91
9 1c NaY 90 22 Yes 90 37 51 1 1 99 98
224870Yes6890NaY 1001001d10e
Yes2490NaY2a11 90 39 48 2 98 98
2690NaY 912b 9112 7372063Yes
a The structures of all products were assigned by GC/MS analyses and by comparison with authentic samples.
b Methylation versus carbamation selectivity, SMet/Carb=[M+D/(M+D+C+MC)]×100.
c Overall N-methyl selectivity, SMet=[M+D/(M+D+C+MC+E)]×100.
d Entry 4: the reaction was carried out in a stainless-steel autoclave of 150 mL.
e Products M, D, C, and MC of entry 10 were obtained according to the structure of the reacting substrate 1d: PhCH(Me)NH2.
M. Sela, P. Tundo / Tetrahedron Letters 44 (2003) 8139–8142 8141
is an intrinsic co-product of DMC-mediated methyla-
tion reactions. As far as the methylation proceeds, CO2
chemisorbs into the catalyst cages,6 where it becomes
available for the reactant amine to form the corre-
sponding urethanes (Eq. (1)).7
2RNH2+CO2 RNHCO2− RNH3+ 
DMC
RNHCO2Me
(1)
The BAc2 mechanism of Scheme 2 through the attack of
the amine to the carbonyl of DMC cannot take place
directly. On the other hand, when the zeolite surface is
kept free from CO2, the carbamation is hindered and
the aliphatic amine reacts only via the BAl2 mechanism:
N-methylation takes place exclusively (Eq. (2)).
(2)
It should be noted that this behavior is peculiar to the
explored conditions and particularly to the catalyst
used. While the reaction of aliphatic amines and DMC
does not proceed significantly without a catalyst, in the
presence of -Al2O3, carbamates form in good to excel-
lent yields (80–95%).8 Furthermore, this reaction occurs
without any CO2 promotion: under the conditions of
entries 7–12 of Table 1, benzylamine reacts with DMC
over -Al2O3,9 to give methyl N-benzylcarbamate as the
sole product (24% after 4 h, Scheme 3).
The direct BAc2 attack of the amine on the DMC
carbonyl is allowed in this case.
With Y faujasites, the involvement of CO2 in the reac-
tion of aliphatic amines with DMC may also account
for the lack of mono-N-methyl selectivity in such reac-
tions. In fact, the mechanism proposed for the forma-
tion of mono-N-methylanilines as well as
mono-C-methyl derivatives of CH2-active com-
pounds—though with different catalysts—involves the
sequence shown in Scheme 4.1,10 The nucleophile
(NuH2) reacts first with DMC via the BAc2 mechanism
to yield the methoxycarbonylated derivative
[Nu(CO2Me)H, Eq. (2)]. Then methylation (BAl2 mech-
anism) and demethoxycarbonylation reactions (Eqs. 5–
6) lead to the final product [Nu(Me)H]. The sequence
of BAc2–BAl2 processes preserves NuH2 from a double
methylation.
By contrast, the more nucleophilic aliphatic amines
directly attack the methyl group of DMC as is shown in
Eq. (2), and when CO2 is purged from the reaction
mixture, a reversible methoxycarbonylation reaction is
not possible. Any selectivity towards mono-N-methyl
products is ruled out.
On the whole, the following conclusions can be drawn:
(i) MY faujasites are efficient catalysts for the N-
methylation of aliphatic amines, but a high
chemoselectivity (methylation versus carbamation)
is reached through the tuning of the acid–base
properties of the zeolites and most of all, through
the removal of CO2 from the reactant mixture;
(ii) The BAl2 displacement of the amine on DMC is
the likely reaction mechanism. Accordingly, since
the mono-N- versus N,N-dimethylation selectivity
cannot be controlled, the procedure has valuable
potential for synthesis of tertiary amines.
Acknowledgements
MIUR (Italian Ministry of University and Research)
and INCA (Interuniversity Consortium Chemistry for
the Environment; grant ‘Piano Ambiente Terrestre:
Chimica per l’Ambiente’ Legge 488/92) are gratefully
acknowledged for financial support.
Scheme 3. Direct BAc2 attack of benzylamine on DMC.
Scheme 4. Mono-methylation selectivity with DMC. NuH2: nucleophile susceptible of double alkylation; B: a basic site of the
catalyst.
M. Sela, P. Tundo / Tetrahedron Letters 44 (2003) 8139–81428142
References
1. (a) Selva, M.; Bomben, A.; Tundo, P. J. Chem. Soc.,
Perkin Trans. 1 1997, 1041–1045; (b) Selva, M.; Tundo,
P.; Perosa, A. J. Org. Chem. 2001, 66, 677–680; (c) Selva,
M.; Tundo, P.; Perosa, A. J. Org. Chem. 2002, 67,
9238–9247.
2. Selva, M.; Tundo, P. Acc. Chem. Res. 2002, 35, 706–716.
3. The LiY and CsY zeolites were prepared from NaY
through known procedures (Onaka, M.; Ishikawa, K.;
Izumi, Y Chem. Lett. 1982, 1783–1786). The Lewis acid-
ity of these solids is higher with cations having a higher
charge to mass ratio: particularly, Li+ and Na+ mitigate
the amine nucleophilicity and due to their smaller size,
they allow an easier diffusion of reactants through the
zeolite cages. (a) Eberly, P. E. In Zeolite Chemistry and
Catalysis ; 171, ACS Monograph, Rabo J. A., 1976; (b)
Barthomeuf, D. J. Phys. Chem. 1984, 88, 42–45; (c) Rao,
J. V. Chem. Commun. 1998, 269; (d) Su, B.; Barthomeuf,
D. Stud. Surf. Sci. Catal. 1995, 94, 598–605.
4. In all probability, the formation of product E is pro-
moted by O2 traces in the reaction mixture. (a)
Toshikazu, H.; Masayoshy, H.; Isao, I.; Yoshiki, O. J.
Chem. Soc., Chem. Comm. 1993, 194–195; (b) Kim, J. M.;
Cho, I. S.; Mariano, P. S. J. Org. Chem. 1991, 56,
4943–4955.
5. (a) Narayan, S.; Deshpande, K. J. Mol. Catal. 1995, 104,
L109–L113; (b) Fesenko, E. A.; Barnes, P. A.; Parkes, G.
M. B.; Brown, D. R.; Naderi, M. J. Phys. Chem. B. 2001,
105, 6178–6185.
6. Zecchina, A.; Lamberti, C.; Bordiga, S. Catal. Today
1998, 41, 169–177.
7. (a) Aresta, M.; Quaranta, E. Tetrahedron 1991, 47, 9489–
9502; (b) Aresta, M.; Dibenedetto, A.; Quaranta, E.;
Boscolo, M.; Larrson, R. J. Mol. Catal. 2001, 174, 7–13;
(c) Selva, M.; Tundo, P.; Perosa, A. Tetrahedron Lett.
2002, 43, 1217–1219.
8. Vauthey, I.; Valot, F.; Gozzi, C.; Fache, F.; Lemaire, M.
Tetrahedron Lett. 2000, 41, 6347–6350.
9. We used the same -Al2O3 (oxid C) reported in Ref. 8:
this catalyst was a generous gift from Degussa.
10. Selva, M.; Marques, C. A.; Tundo, P. J. Chem. Soc.,
Perkin Trans. 1 1994, 1323–1328.


Selective N-methylation of Primary Aliphatic Amines with Dimethyl Carbonate in the Presence of Alkali Cation Exchanged Y-Faujasites

Archivio Istituzionale della Ricerca

SELVA, Maurizio

TUNDO, Pietro

Archivio istituzionale della ricerca - Università degli Studi di Venezia Ca' Foscari

TETRAHEDRONLETTERSTetrahedron Letters 44 (2003) 8139–8142PergamonSelective N-methylation of primary aliphatic amines withdimethyl carbonate in the presence of alkali cation exchangedY-faujasitesMaurizio Selva* and Pietro TundoDipartimento di Scienze Ambientali dell’Universita` Ca’ Foscari, Calle Larga S. Marta 2137, 30123 Venezia, ItalyReceived 17 July 2003; revised 18 August 2003; accepted 3 September 2003Abstract—The N-methylation of aliphatic amines [XC6H4(CH2)nNH2; n=1, X=H (1a), o-MeO (1b), p-MeO (1c); n=2, X=H(2a), o-MeO (2b); 1d: PhCH(Me)NH2] with dimethyl carbonate (DMC) is efficiently catalysed by NaY faujasite: on condition thatCO2 (a co-product of the reaction) is carefully removed, N-methyl- and N,N-dimethyl-amines (RNHMe and RNMe2) areobtained in good overall yields (70–90%). Otherwise, in the presence of CO2, carbamates (RNHCO2Me) form competitively to alarge extent. The reaction probably proceeds through a BAl2 displacement of the amine on DMC.© 2003 Elsevier Ltd. All rights reserved.In the presence of alkali cation exchanged Y-faujasites(e.g. NaY and KY), the reaction of dimethyl carbonatewith primary aromatic amines affords the correspond-ing mono-N-methyl derivatives with unprecedentedselectivity (92–99%). This holds even for anilines deacti-vated by both electronic and steric effects (Scheme 1).1Besides the synthetic outcome, this reaction shows rele-vant environmentally benign features: it uses a non-toxic methylating agent (DMC) coupled with eco-safesolids (zeolites) as catalysts, it does not require addi-tional solvents, and neither organic nor inorganic by-products are formed.2As a part of our research program on the reactivity ofDMC over Y zeolites, we were interested in the N-methylation of primary aliphatic amines as well. Thehigher nucleophilicity of these substrates posed a severelimitation to the reaction selectivity, due not only tothe double N-methylation but primarily, to the forma-tion of carbamates (Scheme 2).1a,c Apparently,BAc2 and BAl2 mechanisms, i.e. the attack of the amineto the carbonyl (BAc2) and to the methyl (BAl2)groups of DMC, were possible without any discrimina-tion.In this paper, we wish to report a further investigationon this reaction which discloses the synthetic potentialfor the preparation of N-methyl amines and somerelevant features of the methylation/methoxycarbonyla-tion mechanisms of aliphatic amines with DMC.Initially, benzylamine 1a, o- and p-methoxybenzyl-amine, and (-methyl)benzylamine (compounds 1b, 1c,and 1d respectively) were chosen as substrates (Table1). In a typical procedure (entry 7), a three-necked,jacketed, 25 mL round-bottomed flask fitted with aN2-bubbler, an adapter for the withdrawal of samples,a reflux condenser connected to a gas flowmeter, and amagnetic bar, was loaded with a solution of benzyl-amine (1a, 0.3 g, 2.8 mmol) in dimethyl carbonate (20mL), and NaY (0.9 g). The flask was heated at thereflux temperature of DMC (90°C), while the mixturewas vigorously stirred. A N2 flow of 25 mL/min wasScheme 1. Mono-N-methylation of anilines with DMC.* Corresponding author. Tel.: +39 041 234 8687; fax: +39 041 234 8620; e-mail: selva@unive.it0040-4039/$ - see front matter © 2003 Elsevier Ltd. All rights reserved.doi:10.1016/j.tetlet.2003.09.016M. Sela, P. Tundo / Tetrahedron Letters 44 (2003) 8139–81428140Scheme 2. R=CH2Ph, Cy.ucts C and MC, Scheme 2) and the oxidative deamina-tion (product E: XC6H4CH2N=CHPh) of the amine 1atake place to a large extent.4 The Bro¨nsted acidic zeolite(HY) is even more unsatisfactory (entry 6): at a 30%conversion, SMet is only 33%. We suggest that a strongacid-base interaction may hold amine within the cata-lyst pores,5 so that any advantage due to the smallersize of the cation is cancelled.Much better results can be gathered for the N-methyla-tion of compound 1a as well as of 1b–d, when reactionsare performed over NaY—a commercially availablefaujasite—in the presence of a N2 stream (entries 7–10):SMet of 91–100% are attained at conversions of 70–94%.This improvement arises not only from the increaseof the methylation versus carbamation selectivity(SMet/Carb), but also from a fall in formation of theside-product E.The same procedure is profitable also for the reactionof phenethylamine (2a) and its o-methoxyderivative [2b:o-MeOC6H4(CH2)2NH2] with DMC. The presence of aN2 flow is an extremely simple and efficient method toallow an excellent N-methylation selectivity (91–98%)for compounds 2a–b, while the carbamation reaction ispractically ruled out.The data in Table 1 give a clear indication of the majorrole played by the CO2 which, as is shown in Scheme 1,bubbled into the mixture and mantained throughoutthe reaction. At intervals, samples (0.1 mL) were with-drawn and were analyzed by both GC and GC/MS.The structures of the products were also confirmed bycomparison with authentic samples of N-methylbenzyl-amine, N,N-dimethylbenzylamine, methyl N-benzylcarbamate, and methyl N-benzyl, N-methyl carbamate.The same reaction was also performed under a staticN2-atmosphere (entries 1–6).According to our previous experiments,1c without theN2-bubbling, the increase of Lewis acidity of the cata-lyst (going from CsY to LiY faujasites)3 shows a posi-tive effect on the reaction rate (compare entries 1–2 and5).However, at higher conversions (89 and 97%: entries3–4), the selectivity (SMet) towards the N-methylationreaction is clearly variable (43 and 64%, respectively).Competitive side reactions, i.e. the carbamation (prod-Table 1. N-Methylation of amines 1a–d and 2a–b with DMC over MY zeolitesSMet/Carbb (%)Products (%)a SMetc (%)MY T (°C)AmineEntry t (h) N2 flow D C MC EMConv. (%)1a LiY 90 7 No 43 34 9131a NaY 90 7 No 40 30 726474121374983 89No5690NaY1a27 12 49 43NaY 1104d 231a No 97 - 42 165 721081836No2290CsY1a5512846 3330No2390HY1a61a 1 98 96NaY 90 48 Yes 94 20 70 371b NaY 90 23 Yes 708 30 34 5 1 91 919 1c NaY 90 22 Yes 90 37 51 1 1 99 98224870Yes6890NaY 1001001d10eYes2490NaY2a11 90 39 48 2 98 982690NaY 912b 9112 7372063Yesa The structures of all products were assigned by GC/MS analyses and by comparison with authentic samples.b Methylation versus carbamation selectivity, SMet/Carb=[M+D/(M+D+C+MC)]×100.c Overall N-methyl selectivity, SMet=[M+D/(M+D+C+MC+E)]×100.d Entry 4: the reaction was carried out in a stainless-steel autoclave of 150 mL.e Products M, D, C, and MC of entry 10 were obtained according to the structure of the reacting substrate 1d: PhCH(Me)NH2.M. Sela, P. Tundo / Tetrahedron Letters 44 (2003) 8139–8142 8141is an intrinsic co-product of DMC-mediated methyla-tion reactions. As far as the methylation proceeds, CO2chemisorbs into the catalyst cages,6 where it becomesavailable for the reactant amine to form the corre-sponding urethanes (Eq. (1)).72RNH2+CO2 RNHCO2− RNH3+ DMCRNHCO2Me(1)The BAc2 mechanism of Scheme 2 through the attack ofthe amine to the carbonyl of DMC cannot take placedirectly. On the other hand, when the zeolite surface iskept free from CO2, the carbamation is hindered andthe aliphatic amine reacts only via the BAl2 mechanism:N-methylation takes place exclusively (Eq. (2)).(2)It should be noted that this behavior is peculiar to theexplored conditions and particularly to the catalystused. While the reaction of aliphatic amines and DMCdoes not proceed significantly without a catalyst, in thepresence of -Al2O3, carbamates form in good to excel-lent yields (80–95%).8 Furthermore, this reaction occurswithout any CO2 promotion: under the conditions ofentries 7–12 of Table 1, benzylamine reacts with DMCover -Al2O3,9 to give methyl N-benzylcarbamate as thesole product (24% after 4 h, Scheme 3).The direct BAc2 attack of the amine on the DMCcarbonyl is allowed in this case.With Y faujasites, the involvement of CO2 in the reac-tion of aliphatic amines with DMC may also accountfor the lack of mono-N-methyl selectivity in such reac-tions. In fact, the mechanism proposed for the forma-tion of mono-N-methylanilines as well asmono-C-methyl derivatives of CH2-active com-pounds—though with different catalysts—involves thesequence shown in Scheme 4.1,10 The nucleophile(NuH2) reacts first with DMC via the BAc2 mechanismto yield the methoxycarbonylated derivative[Nu(CO2Me)H, Eq. (2)]. Then methylation (BAl2 mech-anism) and demethoxycarbonylation reactions (Eqs. 5–6) lead to the final product [Nu(Me)H]. The sequenceof BAc2–BAl2 processes preserves NuH2 from a doublemethylation.By contrast, the more nucleophilic aliphatic aminesdirectly attack the methyl group of DMC as is shown inEq. (2), and when CO2 is purged from the reactionmixture, a reversible methoxycarbonylation reaction isnot possible. Any selectivity towards mono-N-methylproducts is ruled out.On the whole, the following conclusions can be drawn:(i) MY faujasites are efficient catalysts for the N-methylation of aliphatic amines, but a highchemoselectivity (methylation versus carbamation)is reached through the tuning of the acid–baseproperties of the zeolites and most of all, throughthe removal of CO2 from the reactant mixture;(ii) The BAl2 displacement of the amine on DMC isthe likely reaction mechanism. Accordingly, sincethe mono-N- versus N,N-dimethylation selectivitycannot be controlled, the procedure has valuablepotential for synthesis of tertiary amines.AcknowledgementsMIUR (Italian Ministry of University and Research)and INCA (Interuniversity Consortium Chemistry forthe Environment; grant ‘Piano Ambiente Terrestre:Chimica per l’Ambiente’ Legge 488/92) are gratefullyacknowledged for financial support.Scheme 3. Direct BAc2 attack of benzylamine on DMC.Scheme 4. Mono-methylation selectivity with DMC. NuH2: nucleophile susceptible of double alkylation; B: a basic site of thecatalyst.M. Sela, P. Tundo / Tetrahedron Letters 44 (2003) 8139–81428142References1. (a) Selva, M.; Bomben, A.; Tundo, P. J. Chem. Soc.,Perkin Trans. 1 1997, 1041–1045; (b) Selva, M.; Tundo,P.; Perosa, A. J. Org. Chem. 2001, 66, 677–680; (c) Selva,M.; Tundo, P.; Perosa, A. J. Org. Chem. 2002, 67,9238–9247.2. Selva, M.; Tundo, P. Acc. Chem. Res. 2002, 35, 706–716.3. The LiY and CsY zeolites were prepared from NaYthrough known procedures (Onaka, M.; Ishikawa, K.;Izumi, Y Chem. Lett. 1982, 1783–1786). The Lewis acid-ity of these solids is higher with cations having a highercharge to mass ratio: particularly, Li+ and Na+ mitigatethe amine nucleophilicity and due to their smaller size,they allow an easier diffusion of reactants through thezeolite cages. (a) Eberly, P. E. In Zeolite Chemistry andCatalysis ; 171, ACS Monograph, Rabo J. A., 1976; (b)Barthomeuf, D. J. Phys. Chem. 1984, 88, 42–45; (c) Rao,J. V. Chem. Commun. 1998, 269; (d) Su, B.; Barthomeuf,D. Stud. Surf. Sci. Catal. 1995, 94, 598–605.4. In all probability, the formation of product E is pro-moted by O2 traces in the reaction mixture. (a)Toshikazu, H.; Masayoshy, H.; Isao, I.; Yoshiki, O. J.Chem. Soc., Chem. Comm. 1993, 194–195; (b) Kim, J. M.;Cho, I. S.; Mariano, P. S. J. Org. Chem. 1991, 56,4943–4955.5. (a) Narayan, S.; Deshpande, K. J. Mol. Catal. 1995, 104,L109–L113; (b) Fesenko, E. A.; Barnes, P. A.; Parkes, G.M. B.; Brown, D. R.; Naderi, M. J. Phys. Chem. B. 2001,105, 6178–6185.6. Zecchina, A.; Lamberti, C.; Bordiga, S. Catal. Today1998, 41, 169–177.7. (a) Aresta, M.; Quaranta, E. Tetrahedron 1991, 47, 9489–9502; (b) Aresta, M.; Dibenedetto, A.; Quaranta, E.;Boscolo, M.; Larrson, R. J. Mol. Catal. 2001, 174, 7–13;(c) Selva, M.; Tundo, P.; Perosa, A. Tetrahedron Lett.2002, 43, 1217–1219.8. Vauthey, I.; Valot, F.; Gozzi, C.; Fache, F.; Lemaire, M.Tetrahedron Lett. 2000, 41, 6347–6350.9. We used the same -Al2O3 (oxid C) reported in Ref. 8:this catalyst was a generous gift from Degussa.10. Selva, M.; Marques, C. A.; Tundo, P. J. Chem. Soc.,Perkin Trans. 1 1994, 1323–1328.

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Selective N-methylation of Primary Aliphatic Amines with Dimethyl Carbonate in the Presence of Alkali Cation Exchanged Y-Faujasites

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