Title of Invention	AN IMPROVED PROCESS FOR THE PREPARATION OF B-AMINO ALCOHOLS
Abstract	The present invention provides an improved process for the preparation of & amino alcohols. More particularly it provides an improved proces^po&W^ preparation of (3-amino alcohols by N-alkylation of anilines with an alkylene carbonate in the presence of a heterogeneous catalyst.

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FIELD OF THE INVENTION This invention relates to an improved process for the preparation of (3-amino alcohols. More particularly it relates a process for the preparation of p-amino alcohols by N-alkylation of anilines with an alkylene carbonate in the presence of a heterogeneous catalyst. BACKGROUND OF THE INVENTION P-amino alcohols are extensively used in medicinal chemistry in the preparation of biologically active natural and synthetic products, artificial amino acids, and chiral auxiliaries for asymmetric synthesis. They are also useful as intermediates in the synthesis of perfumes, dyes and photo developers, p-amino alcohol is a versatile organic intermediate in the synthesis of several important organic compounds having different functionalities e.g. oxazolidones can be easily obtained by reacting i-amino alcohols with carbonylating reagents such as phosgene, alkyl carbonates, urea and carbon dioxide. The synthesis of p-amino alcohols from alkylene carbonate and aniline is attractive due to non-hazardous nature of alkylene carbonate over alkylene oxide used as starting material in conventional production. The drawback of conventional methodology is that it involves handling of potentially hazardous alkylene oxide and often catalysts used are corrosive and costly In addition, alkylation employing an alkylene carbonate does not require the high-pressure equipment often necessary when working with the highly volatile alkylene oxide. In most cases, the carbonate acts both as reactant and as solvent. N-alkylation and alkoxy carbonylation of amines by dimethyl carbonate to A/-alkyl amine and carbamate respectively is known, however a similar reaction of alkylene carbonates for the formation of (3 -amino alcohols is not well investigated. It has been reported that reaction between amine and alkylene carbonate gives polymeric products having carbamate and carbonate functionality. Kaye et al. (J. Org. Chem., 1953, 18, pp. 664-668) reported the synthesis of A/-methyl A/-phenyl ethanolamine from A/-methyl aniline and ethylene carbonate using corrosive and flammable homogeneous lithium amide catalyst. Union Carbide Chemicals & Plastics Technology Corporation developed a process (King S.W., US Patent 5,104,987; April 14, 1992) for the alkoxylation of an active hydrogen containing compound comprising contacting the active hydrogen-containing compound with an alkylene carbonate in the presence of a mixed metal oxide catalyst a product mixture having alkoxylation products which constitutes oxyalkylene units of about 18 to 40 weight percent of the is reportedly produced. However, in this patent synthesis of p-amino alcohols from amines and alkylene carbonate is not described. The prior art literature on this reaction revealed that the use of solid base catalysts such as mixed metal oxides and hydrotalcite could be effective. However, these catalysts show poor activity and are not attractive from synthetic of view. There are industrial reports on reaction of ethylene carbonate and propylene carbonate with compounds containing active hydrogen atom in the presence of KaCOa to give polymeric hydroxy alkyl derivatives [Dow Chemical U.S.A., Experimental Ethylene carbonate XAS-1666.00L Product Bulletin 1982, pp. 4-9; Texaco Chemical Company, TEXACAR.RTM. Ethylene and Propylene carbonates Product Bulletin 1987, pp. 23-24]. This patent describes the synthesis of i-amino alcohols using a green chemistry approach, wherein the conventional reagent epoxides (which are toxic and hazardous) are replaced with alkylene carbonates a benign reagent using heterogeneous recyclable catalyst (See Scheme A). The use of solid base catalysts for organic synthesis is increasing because these catalysts are safe to handle, non-corrosive, low cost, have long shelf life and easily available commercially. In this context zeolites are promising due to their micro porous, alumino silicate structure with highly ordered crystalline nature. The combination of acid and base properties and shape selectivity in the zeolite catalyst is an important factor for synthesis of fine chemicals; particularly faujasites are often employed as preferred catalysts for various types of the reactions like alkylation, isomerization, polymerization, cyclization, nitrile hydrolysis, photo reduction, nitration of aromatic compounds etc. From industrial point of view, alkylene carbonates are important precursors. Ethylene carbonate and propylene carbonate have been available commercially for over 40 years and have numerous applications as both reactive intermediates and inert solvents. They have additional properties like, high boiling and flash point, low odor level and evaporation rates, low toxicities and biodegradable which are appreciable and they can react with an active hydrogen containing compounds like, amines, alcohols, thiols and carboxylic acids (Clements J.H.; Ind. Eng. Chem. Res., 2003,42, pp 663-674). (Table Remove) OBJECTS OF THE INVENTION The main object of the present invention is to provide an improved process for preparation of (3-amino alcohol using substituted anilines and alkylene carbonates as starting material heterogeneous catalyst. Another object of the invention is to provide a non-epoxide and hence less hazardous and environmentally benign process. Yet another object is to provide a single pot reaction to produce (3-ammo alcohol that utilizes environmentally benign reactants such as organic carbonates. Still another object of the present invention is the use of Na-Y zeolite catalyst which is stable and recyclable and not corrosive or hazardous. Further object of the invention is to provide a simple and inexpensive route to p-amino alcohol synthesis. SUMMARY OF THE INVENTION Accordingly, the present invention provides an improved process for the preparation of p-amino alcohol which comprises reacting an amine with an organic cyclic carbonate in an organic solvent in the presence of a heterogeneous catalyst, at a temperature in the range of 120°C to 200°C, for a period of about 5 minutes to 12 hours, under stirring, and recovering the desired product of (3-amino alcohol by known method. In an embodiment of the present invention the amine used has a general formula 2 R1NHR2 Formula 2 wherein, R-, is selected from the group consisting of Cyclohexyl (C6Hii), benzyl (C6H5-CH2) and x-C6H4 wherein x = H, CH3, OCH3, NH2, Cl, OH, or NO2 and R2 is selected from H, CH3 and C2H5. In yet another embodiment the amine used is selected from the group consisting of aniline, p-toluidine, p-anisidine, p-chloro aniline, p-nitro aniline, p-phenylene diamine, m-amino phenol, benzyl amine, cyclohexyl amine, N-methyl aniline In yet another embodiment the organic cyclic carbonate used has a general formula 3 o R formula 3 wherein, n =1 or 2; R is selected from H, CH3, C2H5 and C6H5. In yet another embodiment the heterogeneous catalyst used is selected from the group consisting of alkali or alkaline earth metal ions exchanged zeolite selected from NaOH or KOH impregnated on H-ZSM-5 and alkali or alkaline earth metal ions exchanged faujasites X and Y selected from Na-Y, Cs-Na-Y, Na-X and Cs-Na-X, impregnated faujasites selected from NaOH or KOH impregnated on X, Y faujasites and mounted base selected from NaOH, KOH and K2CO3 alkali and alkaline earth metal on silica gel or alumina. In yet another embodiment the heterogeneous catalyst used is preferably selected from the group consisting of Na-X, Na-Y, Cs-Na-X and Cs-Na-Y In yet another embodiment the heterogeneous catalyst is recyclable for further use for at east 5 times without significant loss in its activity. In yet another embodiment the amount of heterogeneous catalyst used is in the range of 0.5 to 10 %. An improved process as claimed in claim 1, wherein the amount of amine used is in the range of about 1 to 80 %, preferably in the range of about 10% to 70%. In yet another embodiment the organic cyclic carbonate used is in the range of 10 % to 99 %, preferably in the range of about 20 % to 75 %. In yet another embodiment the organic used is selected from the group consisting of an inert solvent, polar and non-polar solvent. In yet another embodiment the organic solvent used is selected from the group consisting of toluene, ethylene glycol, diphenyl ether, dodecane, N-methyl pyrolidinone and glyme selected from tri(ethylene glycol) dimethyl ether and tetra(ethylene glycol) dimethyl ether. In yet another embodiment the reaction temperature used is preferably in the range of 90°C to 200°C. In yet another embodiment the p-amino alcohol obtained has a general formula 1 formula 1 wherein, R^ is selected from the group consisting of cyclohexyl (C6Hn); benzyl (C6H5-CH2) and x-C6H4 wherein x = H, CH3, OCH3, NH2, Cl, OH or NO2; R2 is selected from H, CH3 and C2H5 ; R3 is selected from H, CH3, C2H5 and C6H5 ; R4 is selected from H, CH3, C2H5andC6H5 In yet another embodiment the % conversion of amine is in the range of 80 to 100. In yet another embodiment the % yield of N-phenyl ethanolamine is about 96% with 100% amine conversion, when Na-X is used as a catalyst. In yet another embodiment the % selectivity of N-phenyl ethanolamine is 100% with 100% amine conversion when Na-Y is used as a catalyst. In yet another embodiment the % yield of N-phenyl ethanolamine is about 95% with 100% amine conversion, when Cs-Na-x is used as a catalyst. In still another embodiment the % yield of N-phenyl ethanolamine is about 86% with 86% amine conversion, when Cs-Na-Y is used as a catalyst. DETAILED DESCRIPTION OF THE INVENTION The present invention provides a process for the preparation of l-amino alcohols of general formula (1) R1NR2CHR3CHR4OH Wherein, R, = Cyclohexyl (C6Hn); benzyl (C6H5-CH2), x-C6H4 (x = H, CH3, OCH3, NH2, Cl, OH, NO2). R2 = H, CH3, C2H R — LJ /"* LJ O LJ (^ LJ 4- n, Un3, O2ri5, Ogns which comprises reacting anilines having general formula (2) R1NHR2 with an alkylene carbonates in presence of Na-Y zeolite as a solid base catalyst and solvent at a temperature in the range of 90 °C to 200 °C for 0.5 to 72 h under constant agitation, recovering the catalyst by filtration and isolating the product by conventional flash chromatography. (3-amino alcohols may have a general formula (1), RiNR2CHR3CHR4OH Wherein, Ri = Cyclohexyl (C6Hn); benzyl (C6H5-CH2), x-C6H4 (x = H, CH3, OCH3, NH2, Cl, OH, N02); R2 = H, CH3, C2H5; R3 = H, CH3l C2H5, C6H5; R4 = H, CH3, C2H5, C6H5. and amine may have general formula (2); RiNHR2 wherein Ri = Cyclohexyl (C6Hn); benzyl (C6H5-CH2), x-C6H4 (x = H, CH3, OCH3, NH2, Cl, OH, NO2) and R2 = H and when R1 = x-C6H4 (x = H, CH3, OCH3, NH2, Cl, OH, NO2); R2 = CH3, C2H5.The alkylene carbonate may have the formula (3) R wherein, n =1; R = H, CH3, C2H5, C6H5 and when n = 2; R = H. The catalysts used may be solid bases, which can be used alone or in combination with others, and may be selected from following compounds (I) Catalyst, selected from aluminosilicate of mineral faujasite structure zeolites X or Y or L type or a combination thereof such as alkali ions exchanged Zeolites like, Na or K-Y or Cs-Na-Y or Cs-Na-X or K-L zeolite and/or alkali impregnated zeolites such as NaOH or KOH impregnated on H-Y zeolite (II) Mounted bases such as NaOH, KOH, K2CO3, alkali metal and alkaline earth metal on silica gel, alumina In a feature of the present invention the reaction between asymmetric alkylene carbonate and aniline yield two possible asymmetric products, which may be illustrated by reaction Scheme B as follows: Scheme B: () R A Jl NaY Zeolite /=\ OH /—\ JL I M u *» v_ * .. H R R In the present invention chiral amino alcohols may be synthesized using chiral alkylene carbonates. In the present invention the reaction between asymmetric cyclic carbonate and aniline yield four possible asymmetric products which may be illustrated by reaction Scheme C as follows: Scheme C: -, |R) V H (2R)- 2-anilinopropane-l-ol (XXIIA| (Figure Remove) (Figure Remove)-NH2 + H CH3 (2$)- l-anitinopropane-2-ol [XXIB| (2S)- 2-anilinopropanc-l-ol |\XIIB| In a feature of the present invention the reaction should be conducted under the condition of vigorous stirring so that all the reactants and catalyst remain in well-mixed state and catalyst is well suspended in liquid phase. Generally a stirrer speed in the range of 100-1500 rotation per minute (rpm) is employed and more preferably stirrer speed in the range 500-1000 rpm is necessary. In another feature of the present invention the solid base catalyst may be recycled several times in the process so as to increase the efficiency of the catalyst and productivity of (3-amino alcohol formation. An improved process for the preparation of amino alcohols as fully described herein before with reference to the examples 1 to 47. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. The Na-Y zeolite catalyst employed in the examples are, commercially available Na-Y zeolite catalyst supplied by e.g. Sudchemi, India. However, any other commercial supplier/manufacturer of Na-Y zeolite may also be employed as a convenient source of catalyst. The invention is further illustrated by the following examples, which should not however be construed to limit the scope of the present invention. EXAMPLE 1 1.07 x 1CT2 mol of aniline, 1.3 x10"2 mol ethylene carbonate, 1.55 x 1CT2 mol of triglyme as solvent and 250 mg Na-Y zeolite as catalyst (calcined at 500 °C for 6 h, Sud Chemie, India) were charged to a well flushed and dried 3-necked round bottom glass reaction vessel (50 cc) equipped with a temperature controller and indicator, stirrer and reflux condenser. The contents were heated under stirring upto 160 °C and kept for 0.5 h while inert atmosphere (nitrogen) was maintained. After cooling to room temperature, the reaction mixture was filtered to separate the catalyst from reaction crude, the reaction mass (filtrate) was analyzed on gas chromatogrph (GC) on a HP-1 capillary column with 30 M length, 0.32 mm inner diameter and film thickness 0.25 nm. Conversion of aniline and yield of A/-phenyl ethanolamine (NPEA) were determined using authentic compounds. Analysis of reaction crude by GC showed conversion of aniline to be 100 % and yield of A/-phenyl ethanolamine to be 100 % and no formation of A/-phenyl diethanolamine (NPDEA). A/-phenyl ethanolamine was also isolated in pure form by column chromatography (silica gel, hexane-ethyl acetate 95:5) and characterized by elemental analysis, 1H NMR, 13C NMR, IR. This proceedure was repeated for all catalyst screening experiments (Example 2-19), temperature study experiments (Examples 26-28 ) and solvent screening experiments (Examples 29-33) and their results were tabulated in Table 1, Table 2 and Table 4 respectivly. (Figure Remove) ,OH OH Vphciiyl ethanolamine N-phenyl diethanolamine Tablel: Remove (Figure Remove)= 0.25g;b= 1.8x10 mol EXAMPLE 20 The procedure in example-1 was exactly repeated for the catalyst recycle study. After completion of reaction (Example- 20), Na-Y catalyst was recovered from the reaction mixture by filtration and was washed with acetone, dried at 100 °C and then calcined at 500 °C for six hours in air. This calcined catalyst was charged to the glass reactor along with 1.07 x 10~2 mol of aniline, 1.3 x10"2 mol ethylene carbonate, 1.55 x 10~2 mol of triglyme as solvent. After cooling the reaction mass to room temperature catalyst was recovered by filtration and the GC analysis of reaction crude showed 100 % aniline conversion and yield of N-phenyl ethanolamine to be 100 %. This procedure was followed for five recycle experiments and results were tabulated in Table 2 (Examples 20 to 25). Table Remove Synthesis of 3-amino alcohol at various temperatures Entry Temperature, °C Time Aniline NPEA (Table Remove)1.07 x 10"2 mol of amine, 1.3 x10"2 mol ethylene carbonate, 1.55 x 10 2 mol of triglyme as solvent and 250 mg Na-Y zeolite as catalyst (calcined at 500 °C for 6 h, Sud Chemie, India) were charged to a well flushed and dried 3-necked round bottom glass reaction vessel (50 cc) equipped with a temperature controller and indicator, stirrer and reflux condenser. The contents were heated under stirring up to 160 °C (for cyclohexyl amine, reaction temperature was 134 °C, Example-41) and kept for 0.5 to 12 h while inert atmosphere (nitrogen) was maintained. After cooling to room temperature, the reaction mixture was filtered to separate the catalyst from reaction crude; the reaction mass (filtrate) was analyzed on gas chromatograph (GC) on a HP-1 capillary column with 30 M length, 0.32 mm inner diameter and film thickness 0.25 )m. Conversion of amine and yield of p-amino alcohols and other side products were determined and results were tabulated in Table 5 (Examples 34 to 42). (Table Remove) EXAMPLE 43 1.07 x 10"2 mol of aniline, 1.3 x 10"2 mol 1,2 propylene carbonate, 1.55 x 1CT2 mol of triglyme as solvent along with 250 mg of Na-Y zeolite as catalyst (calcined at 500 °C for 6 h, Sud Chemie, India) were charged to a well flushed and dried 3-necked round bottom glass reaction vessel (50 cc) equipped with a temperature controller and indicator, stirrer and reflux condenser. The contents were heated under stirring up to 160 °C for 7 h. After completion of reaction , reaction mixture was analyzed on GC (HP-5 capillary column, 30M x 0.32 mm ID x 0.25 "im film thickness) and GC analysis showed 100 % aniline conversion and yield of 1-anilino propane 2-ol to be 92 % and yield of 2-anilino propane 1-ol to be 8 %. The crude is a recemic mixture of 1-anilino propane 2-ol and 2-anilino propane 1-ol. The four optical isomers (See Scheme C) were analysed using chiral HPLC as follows: chiral column: Dicel chiral OD-H column; hexane:/-PrOH (97.5:2.5 %, V/V), flow rate 1 ml/ min; ti= 42.2 min; 2R-2-anilino propane 1-ol XXIIA, t2= 45.2 min; 2R-1-anilino propane 2-ol XXIA; t3= 58.2 min 2S-1-anilino propane 2-ol XXIB; U= 60.0 min; 2S-2-anilino propane 1-ol XXIIB; (See Scheme C). Same experiment procedure was followed for Examples 44-45 and Examples 46-47 (except HPLC analysis) and results were tabulated in Table 6. Table 6 Synthesis of amino alcohols using various cyclic carbonates and aniline Entry Cyclic carbonate Time Aniline (h) conv. (%) Amino alcohol Yield (%) Example- 12 43 propylene carbonate 100 92 [XXI] 8 [XXII] H ,CH Example- R(+)1,2 44 propylene carbonate 100 8JXXIIA] (Figure Remove) Example- S(-)1,2 45 propylene carbonate 7 100 92[XXIB] (Figure Remove) H H ^CH, 8 [XXIIB] Example- Styrene 46 carbonate 8 100 9 [XXIII] 91 [XXIV] 19 H (Figure Remove) OH Example- 1,3 47 propylene carbonate 82 82 [XXV] ADVANTAGES OF THE INVENTION > Invention demonstrates a simple, efficient and environmentally benign methodology for the synthesis of p-amino alcohols starting from benign reactants such as aromatic amines and cyclic carbonate. v The process utilizes a solid base catalyst Na-Y zeolite, which is inexpensive, highly efficient and recyclable. >• The process consists of a simple experimental set-up. y The process produces only carbon dioxide, which is innocuous side product, and hence the process is benign. We claim 1 An improved process for the preparation of (3-amino alcohol which comprises reacting an amine with an organic cyclic carbonate in an organic solvent in the presence of a heterogeneous catalyst, at a temperature in the range of 120°C to 200°C, for a period of about 5 minutes to 12 hours, under stirring, and recovering the desired product of (3-amino alcohol by known method. 2. An improved process as claimed in claim 1, wherein the amine used has a general formula 2 Formula 2 wherein, Ri is selected from the group consisting of Cyclohexyl (C6Hn), benzyl (C6H5-CH2) and x-C6H4 wherein x = H, CH3, OCH3, NH2, Cl, OH, or NO2 and R2 is selected from H, CH3 and C2H5. 3. An improved process as claimed in claims 1& 2, wherein the amine used is selected from the group consisting of aniline, p-toluidine, p-anisidine, p- chloro aniline, p-nitro aniline, p-phenylene diamine, m-amino phenol, benzyl amine, cyclohexyl amine, N-methyl aniline 4. An improved process as claimed in claim 1, wherein the organic cyclic carbonate used has a general formula 3 (Figure Remove)wherein, n =1 or 2; R is selected from H, CH3, C2H5 and C6H5. An improved process as claimed in claim 1, wherein the heterogeneous catalyst used is selected from the group consisting of alkali or alkaline earth metal ions exchanged zeolite selected from NaOH or KOH impregnated on H-ZSM-5 and alkali or alkaline earth metal ions exchanged faujasites X and Y selected from Na-Y, Cs-Na-Y, Na-X and Cs-Na-X, impregnated faujasites selected from NaOH or KOH impregnated on X, Y faujasites and mounted base selected from NaOH, KOH and K2CO3 alkali and alkaline earth metal on silica gel or alumina. 6. An improved process as claimed in claim 1, wherein the heterogeneous catalyst used is preferably selected from the group consisting of Na-X, Na-Y, Cs-Na-X and Cs-Na-Y. 7. An improved process as claimed in claim 1, wherein the heterogeneous catalyst is recyclable for further use for at east 5 times without significant loss in its activity. 8. An improved process as claimed in claim 1, wherein the amount of heterogeneous catalyst used is in the range of 0.5 to 10 %. 9. An improved process as claimed in claim 1, wherein the amount of amine used is in the range of about 1 to 80 %, preferably in the range of about 10% to 70% 10. An improved process as claimed in claim 1 wherein the organic cyclic carbonate used is in the range of 10 % to 99 %, preferably in the range of about 20 % to 75 %. 11. An improved process as claimed in claim 1, wherein the organic used is selected from the group consisting of an inert solvent, polar and non-polar solvent. 12. An improved process as claimed in claim 1, wherein an organic solvent used is selected from the group consisting of toluene, ethylene glycol, diphenyl ether, dodecane, N-methyl pyrolidinone and glyme selected from tri(ethylene glycol) dimethyl ether and tetra(ethylene glycol) dimethyl ether. 13. An improved process as claimed in claim 1 wherein the reaction temperature used is preferably in the range of 90°C to 200°C. 14. An improved process as claimed in claim 1, wherein the (3-amino alcohol obtained has a general formula 1 formula 1 wherein, R-i is selected from the group consisting of cyclohexyl benzyl (C6Hfi-CH2) and x-C6H4 wherein x = H, CH3, OCH3, NH2, Cl, OH or NO2; R2 is selected from H, CH3 and C2H5; R3 is selected from H, CH3, C2H5 and C6H5 ; R4 is selected from H, CH3, C2H5 and C6H5 15. An improved process as claimed in claim 1, wherein the % conversion of amine is in the range of 80 to 100. 16. An improved process as claimed in claim 1, wherein the % yield of N- phenyl ethanolamine is about 96% with 100% amine conversion, when Na-X is used as a catalyst. 17. An improved process as claimed in claim 1, wherein the % selectivity of N- phenyl ethanolamine is 100% with 100% amine conversion when Na-Y is used as a catalyst. 18. An improved process as claimed in claim 1, wherein the % yield of N- phenyl ethanolamine is about 95% with 100% amine conversion, when Cs-Na-x is used as a catalyst. l(>. An improved process as claimed in claim 1, wherein the % yield of N- phenyl ethanolamine is about 86% with 86% amine conversion, when Cs- Na-Y is used as a catalyst. 20. An improved process for the preparation of p-amino alcohols, substantially as herein described with reference to the examples accompanying this specification.

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