Articles Indian Journal of Chemical Tec hno logy Vol. 10, May 2003, pp. 247-250
An efficient liquid phase mono acylation of alcohols, diacylation and dimethoxylation of aldehydes over ZSM-35 R Sri vastava & N Venkatathri * Catalysis Di vis io n, National Chemical Laboratory, Pune 41 1 008, India
Received 30 OCiober 2002; revised received II March 2003; accepted 20 March 2003
ZSM-35, a medium pore zeolite has been synthesized using ethylene diamine as an organic template. The catalyst was found to be an active catalyst for cbemoselective catalytic acylation of alcohols and diacetylation and dimethoxylation of aldehydes.
ZSM-35 has been sy nthesized us ing ethy lenediamine as an organic template origi nally patented by Plank 1 et a/ • It is a medium pore zeolite with FER (Ferrierite) topolog/ with one dimensional channel system of I 0 membered rings (4.2x5.4 A) and another one dimensional channel system perpendicularly intersected, thus ZSM-35 containing a spherical cavity of about 6-7 A3 . Skeleton isomerisation of linear olefins is extensively studied both academ icall y and practically. Especially the production of isobutene by catalytic method to meet the oxygen conte nt of the reformulated gasoline has attracted many industrial researchers. Their efforts were summ arized by Butler 4 and Nicolaides , since then a number of articles have been published on the ske leton isomerisation of linear 7 olefins 5· These isomerisation reactions are due to the acidic nature of the catalyst. Recently various acid 16 such as ZnCh, CO(IT)C1 2. La(Oprh. catalysts 8Sc(Otf) 3 , TMSOtf, TaCI 5-Si0 2. In (Otf) 3 , Cu(Otf) 3 and Zeolite Y have been used for the acy lation reaction of various alcoho ls, amines, etc. This has motivated us to use ZSM-35 as a solid catalyst for the acid catalyzed acylation of alcoho ls. Carbonyl group plays an important role in organ ic chemistry due to its electrophilic nature. Most common problem arises in multi step synthetic route for protecting the carbonyl group from nucleophilic attack. Because of this , protection and deprotection of carbonyl group is sti ll an area of interest in the syn thetic organic chemistry. Many methods have been reported for the synthes is of l , 1 diacetate from aldehyde using protic acids such as su lphuric acid and phosphoric acid, lewis acids lik e zinc choloride and phosphorous(IJI) ch loride and
17
metal oxides based catalyst -22 . These method s have not been ent irely satisfactory owing to such drawback as low yield , long reaction times, corrosiveness and effluent pollution. PC1 3 and B-zeolite have also bee n emp loyed for this purpose. However in most cases either a long reaction time [up to 120 h in case of 2furfuraldehyde with PC1 3 (ref. 24)] or a low yield of product (4% in case of p-nitrobenzaldehyde) is observed. In the present communication a highly efficient liquid phase mono acy lation of alcohol s, diacylation and dimethoxylation of aldehydes over ZSM-35 is reported.
Experimental Procedure Synthesis of ZSM-35 In a typical procedure to sy nthesize ZSM-35 , 3.3g of sod ium alumin ate (99 %, S.D. Fine, India) was mixed well with 0.7g of sodium hydroxide (99 %, S.D. Fine, Indi a) a nd 129 mL of distilled water. This mixture was stirred well until the e ntire solid was dissolved (solution A). Another solution (B) was made by thorough mixing of 46.5g of silica sol (30%, S.D. Fine, India) and ethylene diamine (18.3 g, 99%, Aldrich, U.S.A .) . Solution A and B were mixed well and charged into a Teflon lined steel autoclave. Crystallization was carried out at 450 K for 10 days. The product was removed , washed with deionised water and dried at 383 K for 24h. The zeolite so prepared was subj ected to various physicochemical characterizations.
Characterization *For correspo nd ence (E-mail:
[email protected]. res.in ; Fax: +9 1-020-5893761)
The sample was thoroughly characterized by powder X-ray diffraction (XRD), N 2 adsorption-
Articles
Indi an J. Chem. Techno!.. May 2003
desorption isotherm (s urface area meas urement), FTIR spectroscopy, solid state magic angle spin NMR spectroscopy, scanning electron microsco py (SEM) thermog ravimetric anal ys is. Detailed and characterization of individual technique for the ZSM35 is reported elsewhere23 . The progress of the reaction was monitored by gas chromatography (Varian CX) usi ng a capillary column (C P Si iSCB, id . 0.53 mm and 30 m length) and the structure of the product was identi fied by GC-MS (Shimadzu QP5000) and BRUKER AC200 NMR spectrometer.
Acylation reaction In a typ ical procedure, the substrate (alcoho l/aldehyde compounds) ( I0 mmol) was added to the ace ti c an hyd ride ( II and 2 1 mmol for alcohol and aldehydes respectively) and the mixture was st irred under reflux in acetonitril e (5 mL) in th e presence of ZSM-35 catalyst (20 wt% with respect to the substrate) for stipul ated peri od of time for the completion of th e reaction (monitored by TLC/GC for the co nversion and selecti vity). After completi on of th e reaction, th e catalyst was separated by cen tri fugatio n and the filtrate was co ncentrated, diluted with water, it was th en extracted with ethyl acetate and washed with brine and dried over Na2S04 . The solvent was evaporated to get th e crude product. The crude product was purified by column chromatog raphy over silica gel (60-120 mesh) with ethyl acetate and petroleum ether mi xture. The structure was co nfirmed by GCMS and proton NMR The centrifuged catalyst was spectroscopy. thoroughly washed with water and dried at 300°C and th en recycled for the acy lati on reacti on.
Dimethoxylatiou of aldehydes In a typi cal procedure, the substrate (I 0 mmol) was added to 20 mL of methan ol. The mi xture was stirred at 333 K in the presence of ZSM-35 catalyst (20 wt% with res pect to the substrate) for stipul ated period of time for th e compl eti on of the reaction (monitored by TLC/GC for the conversion and selectivity). After co mp letion of the reaction the catalys t was separated by centrifugation and the solvent was evaporated to get the crude product that was puri fied by column chromatography over silica gel (60- 120 mesh) with ethyl acetate and petroleum ether mixture. The structure was confirmed by GCMS and proton NM R spectroscopy. Resu lts a nd Discussion Table I shows the results obtained in the diacyl ation of a variety of aldehydes with acetic anhydride. The reaction time given in Table 1 also represents th e tim e taken for the completion of the reaction . The result demonstrated th at aldehydes are acy lated very selectiv ely with excellent yields of the acy lated prod ucts. For substi tuti on on the aromatic ring, there is not much difference in the conversion and selecti vi ty (entry 5-6, Table 1). In case of the napthyl and quino line carboxaldehyde (entry 8-9, Table I) the react ion is slow because napth yl moiety is bulky enough to go inside the pore and the avai lability of th e active sites for the reaction will be less so it will take longer time for the completion of th e reacti on. The catalyst can be recyc led for further reacti on without losi ng its catalyt ic activ ity (entry 2-4, Table 1).
Table 1- Diacety lat io n o f va ri o us aldehyde w ith aceti c anhydrid e over ZSM-35 S.No .
Substrate
Co nvers io n
Selec ti vity
Reacti o n ti me( h)
I
Benzaldehyde
96 .2
98.6
4
2
I" recycle"
93.4
98.0
4
3
2"" recyc le"
93.0
97.4
4
4
3'" recycle"
92.2
95.6
4
5
p-Meth oxy benzald ehyde
92.7
93.5
4
91.0
94.6
4
6
p-Ni tro benzaldehyde
7
2-Furald ehyde
93 .5
92.7
6
8
2-Napth aldehyde
55.4
89 .7
10
9
2-Q uin oline c::trboxa ldchyde
51.7
87 .9
10
10
Benzaldehydeh
20.4
98 .9
4
II
C inamald ehydc
82.3
86 .3
6
React io n Co nditi o ns: substrate= IO mmo l: aceti c anh ydride = 21 mmol. ; aceto nitrile= 5 mL: catalys t= 20 wt% with respect to substrate. reactio n tem perature = 358 K. "Cata lyst recycled for diacety lation of benza ldehyde. bReacti o n was done without adding catalyst.
248
Articles
Srivastava & Yenk atathri : Mono acy lati o n of alcohols, diacylation and dimethoxylation of aldehydes over ZSM-35
Table 2- Dimethoxylation of various aldehyde with meth anol over ZSM-35 S.No.
Conversion
Substrate
Selecti vity
Reac ti on time( h)
I
Benzaldehyde
80.2
94.5
6
2
I" recycle"
79.4
94.3
6
3
2"ct recyc le"
77.4
91.7
6
4
3'ct recycle"
78.2
93.8
6
5
p- Meth oxy benza ldehyde
74.9
94 .2
6
6
p-Nitro benzaldehyde
75.2
92.6
6
7
2-Furaldehyde
65.9
88.7
8
8
2- Napth aldehyde
49.5
83 .9
12
9
2-Quino line carboxa ldehyde
43.6
79.3
12
10
Benzaldehydeb
90.5
98.7
28
II
Benzaldehyde
