Jan 29, 2003 - compounds like amino alcohols, amines are selectively acylated at lower temperature. ... chemoselective acylation of functionalized organic compound is one of the most .... by GC-MS (Shimadzu QP-SOOO) and BRUKER. AC200 NMR ... 14 Chauhan K K, Frost C G, Love I & Waite D, Syn Lett, 1999,. 1743.
Indian Journal of Chemistry Vol. 438 , April 2004, pp. 888-891
Note Efficient chemoselective liquid phase acylation of amines, alcohols and bifunctional compounds over ZSM-35 R Sri vastava & N Venkatathri * Catalys is Di vis ion, Nati onal Che mi cal Laboratory, Pune 4 11 008, Indi a E- mail: ve nkat@cata. ncl. res.in
Received 29 January 2003; accepted (revised) 29 August 2003 ZS M-35, is a medi um pore zeo li te, has been sy nthes ized using eth ylene di amine as organi c templ ate . The ca talyst is used in the acy lati on of d ifferent amines, alcoho ls and bi functi onal compound s. This material is found to be ac tive and selecti ve acid catalyst, ex hibits not only very good acti vity but also very hi gh chemo-se lec ti vity towards monoacy lati on o f bifuncti onal co mpounds. This material is more reacti ve fo r smaller orga ni c co mpounds beca use of its pore d imension. In case of bifuncti onal compounds like amino alcohols, amines are selec ti ve ly acyl ated at lower temperature.
IPC: Int.CI.' C 07 B 39/00
ZSM-35 synthesis was originally patented by Plank
et. al. I in a system containing ethyl ene diamine as an organic template. It is a medium pore zeo lite with FER (FeITierite) topologl and has a one-dimensional channel system of 1O-membered rings (4 .2x 5.4 A) and a one-dimensional channel system are perpe ndicul arl y intersected and therefore ZSM-35 contain spherical cavity with a size of about 6-7 A3. Skeleton isomeri sation of linear olefin s was extensively studied both from acade mic and practical point o f view. Specially the production of isobutene by catalyti c method to meet the oxygen content of the re formul ated gaso line has attracted many industri al researchers. 4 Their efforts were summarized by Butler et.al. , since then a number of articles have been publi shed on the skeleton isomeri sation o f linear 0 Iefins 5•7 . These isomeri sati ons are due to the ac id ic nature of the cata lyst which is proved by IR spectroscopy. Recentl y, 9 various acid catalysts such as Z nCl} , CoC1 2 , 13 I2 iO La(Opr)3 , Sc(Otfh", TMSOTf , TaCi s -Si0 2 , In (Otf)314, CU(Otfh I5 , and Zeo lite y l 6 were used fo r the acy lation reacti on for various alcohols, amines etc. This moti vates us to use ZSM-35 as a solid catalyst fo r the acid catalyzed chemoselecti ve acy lati on of amines and bifunctional compounds. It may be menti oned th at
chemoselective acylation of functionalized organic compound is one of the most importa nt and frequently used organic transformation. It provides us not only an efficient and inexpensive route for protecting arruno and bifunctional groups but also produces important organic ester intermediates in multi step synthetic process which is widely employed in the synthesis of fine cherrucal s, pharmaceutical, cosmetic and cherrucal auxili aries I7,'8, Herein we report, for the first time, hi ghly active and selective acylation of alcohols, amines and bifunctional compounds using acetic anhydride and acetic acid as an acylating agent over ZSM-35 ,
Result and Discussion The prese nt procedure of acy lati on is quite general for a wide range of structurally vari ed alcohols and a mines such as open ch ain, cycl ic and aromatic underwe nt acyl ation with acid anhydride and acetic acid, However reaction with benzoic anhydride is found to be slugg ish and hence more time is required for co mple ti on of the reaction (Table I , entry 2), The applicability of thi s catalyst can be clearly vi suali zed in the acetyl ation of polyhydroxy compounds under similar conditions, for examples both aliphatic and arom ati c polyol s were acyl ated in very hi gh yi eld (Table I , e ntri es 7-9), Another noteworthy feature of thi s meth odo logy is th at after ex ha usti ve acetylati on, there is no chan ge in the co nfig urati on of chiral alcohol (Table I, e ntry 10) smooth ly de monstrating the practical utility of this method , In order to explore the generali ty and scope of thi s catalyst, th e procedure has been extended to a vari ety of other substrates such as amines, Thus the aromatic , open ch ain and cycli c amines were acyl ated in the presence of ZSM-35 catalyst. The res ults are show n in Table II, An oth er notabl e feature of th e reacti on is th at even hindered amines we re acy lated in very hi gh y ield (Table II, entri es 8 & 10), In case of substituted aro mati c a mines e lectro n-do nating group-substituted de ri vati ve accelerated the reaction a nd the e lectro nwi thdraw in g gro up re tarded the reacti on (Table II, e ntri es 5-7), In case o f the naphth ylamine (Table I , e ntry 12) the reaction is s low beca use naphth y l moiety is bulky e no ugh to go inside the pore and the avail ability of the acti ve sites fo r th e reac tion w ill be
NOTES
889
Table I -
Acylation of alcohol with acetic anhydride as acylating agents over ZSM-35
Entry No.
Substrate
Anhydride
Reaction time(hr)
Conversion
Selectivity
Yields (%)
I 2
Cyclohexanol Cyclohexanol
AC20 (PhCO)20
2.5 8
98 72
100 99.3
98 71.5
(EtCOh O
2.5
86
99.1
85.2
AC20
2.5
90
98.5
88.6
3
Cyclohexanol
4
Hexan-I-ol
5
Phenol
AC20
2.5
96
98.5
94.5
6
Benzy l alcohol
AC20
2.5
92
98.4
90.5
7
Catechol
AC20
3.5
94
98.2
92.3
8
Ethylene glyco l
AC20
3. 5
95
98.5
93.5
9
Gl ycero l
AC20
4
95
99 .1
94. 1
10
cx-Terpineol
AC20
3.5
90
99.5
89.5
For all the reactions II mmolcs of aceti c anh ydride were used, for diol and triol respecti vely 2 1 mmoles and 3 1 mmoles of aceti c an hydride were used. Table II Entry No. I
Acy lation of amines with aceti c anhydride as acy lating agents over ZSM-35 Substrate
Reaction time (hr)
Conversion
Selecti vity
Yield (0/0)
Cyc lohex ylamine ISI rec ycle"
96
100
96
2
94
99.3
93.3
3
2nd recycle'
90
99. 1
89. 1
rd
4
3 recycle'
90
96.5
86.8
5
Aniline
1.5
95
98.5
93.6
6
p- Nitroan iline
2.5
92
96.8
89.0
7
p-Toludine
I
95
98.7
93.7
8
Diisopropylamine
2
90
98.5
88.6
9
Benzy lamine
1.5
91
99. 1
90. 1
10
Pyrrolidine
2.5
89
99.5
88.5
II
Dieth ylamine
2
90
99 .2
89 .2
12
cx- Naphthylaminc
3
65
98. 1
63.7
13
1,4,7-T riazacyc lononane
6
49
60.5
24.2
" Catalyst was recycl ed fo r the acy lati on reacti on with cyclohexy lamine as a substrate For entry 1,4,7-Tri azacyclononane 3 1 mmoles of aceti c anhydri de were used.
less so it will take longer time for the completi on of the reacti on. The same is also observed in the case of 1,4,7 -triazacyc lononane (Table II, entry 13). The catalyst can be reused for the furth er reaction (Table I, entri es 2-4) shows that the acti vity of the catalys t rcmains sa me and it can be used number o f times. F ro m the industri al point of view, anhydride and acid chl orides are more ex pensive th an the correspondin g carboxy li c ac ids. Therefore, we try th e acylation with aceti c acid of vari ous amines and alcohols and th e results are presented in Table III. Enco uraged by thi s findin g, it was fe lt worth whi le to stud y th e reactivity pattern o f diffe re nt kind
of amino alco ho ls and diol s for acy lation reacti o n. Ve ry good che mo-se lec tivity co uld be ac hi eved prov id ed th e reacti o n are ca rri ed o ut at lo wer temperature. It is observ ed that the acyl ati o n o f 2-aminoeth a nol (Table IV , entry 1) carri ed out at 278 K se lecti ve ly produ ced the correspo ndin g Nacetate o nly , th at too in th e ex ce ll ent yield, leav in g th e hydrox y l g ro up un affec ted . The hig h che mose lectivity obse rv ed may be because o f the g reate r nu c leophilic ity of th e a mine g ro up w ith res pec t to a lco hol. In case o f 1,2-pro panedi o l (Table IV , entry 3) , primary a lcoho li c g roup was acyl ated pre ferenti a ll y over th e seco nd ary o ne.
INDIAN J. CHEM ., SEC 13, APRIL 2004
890
Table 111 -
Acy lati on of amines w ith aceti c acid as acy latin g agents over ZSM -3S Reac ti on ti me (hr)
Conversion
Selec ti vity
Yi eld (%)
Cyelohexy lamine
8
94.6
100
94.6
Entry No.
Substrate
2
A niline
8
92 .5
98 .5
91.1
3
p -Ni troa nili ne
8
90.7
96.7
87. 7
4
p -Toludi ne
8
93.2
98.3
9 1.6
5
Dii sopro py lamine
8
87 .9
98.5
86.5
6
Benzy la mine
8
88. 1
99. 1
87.3
7
Pyrroli dine
12
87.3
99 .5
86.8
8
a-Naphthy lamine
12
64.3
98.4
63 .2
95 .1
9
Cyclohexanol
8
97.6
97.5
10
Phenol
8
98.2
98.3
96.5
II
Hexan- I -ol
8
93.7
98.7
92.4
12
Benzy l alcohol
8
95.2
97.6
92.9
13
a-Terp ineol
8
89.7
98. 5
88.3
Table IV--Chemoselec ti ve acy lati on of alcohol and amine w ith ace tic anhydride as acy lat ing agent over ZS M- 3S Entry o.
Substrate
T emp. (K )
Reac ti on time(hr)
Eth anolam ine IHOC 2H4 NH 21
278
6
HOC 2H4 NH Ac
100195
2
Di ethanolami ne [(HOC 2H sh NI-II
278
10
(HOC2Hs)2N Ac
100/92
3
1,2-Propanediol [CH,CH(OH)C H 20i-1i
298
24
CH )CH(OH)CI-I 2OAc : CI-I ,C1-I(OAc)C H 2OAc
Experimental Section The detail ed c haracteri zati on o f indi vidu al techni que for the ZSM- 35 is a lready publi shed elsewhere l9 . The Ff-IR spectra we re recorded on a Nico let (60S XB). To stud y the nature o f the surface hydroxy l gro ups in the transmittance mode, selfsupporting wafers ( IOmg c nf\ ke pt inside an IR ce ll, were used . Th e sample was acti vated ill Sil u at 673 K under vac uum (10'6 Torr) for 4 hr and then cool ed to 323 K before recording th e spectrum (4cm' l reso lu ti on, averaged o ver 500 scans). The sa mple was the n saturated with NH 3 or pyridine and evac uated at 323 K ( I hr). Th e IR spectrum was recorded in the te mpe rature range of 323 to 673K at lOOK inte rval s with degass ing for I hI' pri or to recording of the spectrum . Preparation of catalyst. In a typi ca l procedure to sy nthesize ZSM-35, 3.3g o f sodium alumin ate (99 % , S. D.Fine, Indi a) was mi xed we ll w ith 0 .7g o f sodium hydroxide (99 %, S .D.Fine, Indi a) and 129g of di still ed wate r. Thi s mi xture was stirred we ll until th e e ntire so lid was di ssolved (so luti on A). Anoth er
Product
Conv/ Yi eld (mole %)
100/ (80 :20)
so luti on B was made by th orough mi xin g of 46.47g of sili ca so l (30 %, S .D.Fine, Indi a) and e th y lene diamine (l 8.3g, 99%, A ldrich , U.S .A.). Sol utio ns A and B were mi xed we ll to ma ke c lear mi xt ure a nd c harged into a Te fl on lined stee l autocl ave. C rystalli zati on was ca rri ed out at 177°C for 10 days. The product was re moved and washed with deio ni sed wate r and the sa mpl e was dri ed at 383 K for 24hr. Catalyst preparati on a nd its characteri zat ion are pu bli shed l9 e lsewh ere . General procedure for acylation reaction: In a typi ca l procedure, the substrate (a lcoho ls/amines/ bi fun cti onal co mpounds) ( 10 mmo les) was added to the acetic anhydride/aceti c acid (1 1 mmo les) and d ry acetonitrile (10 ml ). For di o l and tri o! res pec ti vely 2 1 mmo les and 3 1 mmo les o f aceti c ac id were used (Table I , entri es 7-10). The mi xture was stirred under reflux at the parti cul ar te mperature as th e case may be, in th e presence of ZSM-35 catalyst (20 wt % w ith res pect to the substrate) fo r stipul ated pe ri od of time for the co mpl e ti on of the reacti on (monitored by
NOTES
89 1
TLCIGC for the conve rs ion and selectivity). After
References
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Acknowledgements Authors (RS and NV) th a nk the CSIR, Ne w De lhi for a research fellowship.
