Title of Invention	"AN IMPROVED PROCESS FOR THE SYNTHESIS OF 4,4'-DIAMINODIPHENYL 1-METHANES AND ITS SUBSTITUTED DERIVATIVES"
Abstract	The present invention provides an improved process for the synthesis of 4,4"- diaminodiphenymlethane and its substituted derivatives which comprises adding aromatic amino compound to a mixture of eco-friendly catalysts such as natural clays and kaolins and water in a ratio ranging from 1:100 to 1:500 followed by addition of formaldehyde and continuing the stirring for a period in the range of 0.5 to 1.0 h, and separating the residue obtained from step (i) from the reaction mixture by known methods and purifying by conventional techniques. The process is simple, speedy, selective and eco-friendly with 100% conversion.

Title of Invention

"AN IMPROVED PROCESS FOR THE SYNTHESIS OF 4,4'-DIAMINODIPHENYL 1-METHANES AND ITS SUBSTITUTED DERIVATIVES"

Abstract

The present invention provides an improved process for the synthesis of 4,4"- diaminodiphenymlethane and its substituted derivatives which comprises adding aromatic amino compound to a mixture of eco-friendly catalysts such as natural clays and kaolins and water in a ratio ranging from 1:100 to 1:500 followed by addition of formaldehyde and continuing the stirring for a period in the range of 0.5 to 1.0 h, and separating the residue obtained from step (i) from the reaction mixture by known methods and purifying by conventional techniques. The process is simple, speedy, selective and eco-friendly with 100% conversion.

Full Text	This invention relates to an improved process for the synthesis of 4,4-diaminodiphenylmethanes and its substituted derivatives. The process is simple, speedy, selective and eco-friendly with 100% conversion. Work up procedure requires extraction of the product into hot water from which it is recrystallised. It is well known that clays act as efficient catalysts in acid/base promoted reactions in organic synthesis [J.M. Adams, Applied Clay Science, 2, 309 (1987); P. Laszlo, Ace. Chem. Res., 19, 121 (1986); P. Laszlo, Science, 235, 1473 (1987); A. Cornells, P. Laszlo, Aldrichimica Acta, 21, 97 (1988)]. In particular, acid catalysed reactions promoted by mineral acids or Lewis acids constitute a major area of industrial organic chemistry. Efforts have been made in the past to effectively substitute these toxic corrosive chemicals by mild but efficient solid-acid catalysts. [G.J. Ross, Clays. Clay Miner., 17, 347 (1967); J.H. Clarke et al., J. Chem. Soc., Chem. Com., 1353 (1989); Tennakon et al., J.C.S. Dalton, 2207 (1974); SJ. Barlow, T.W. Bastock, J.H. Clark, S.R. Cullen, J. Chem. Soc. Perkin II, 411 (1994); J. Tateiwa, T. Nishimura, H. Horiuchi, S. Uemura, J. Chem. Soc. perkin I, 3367 (1994); C. Collet, A. Delville, P. Laszlo, Angew. Chem. Int. Ed. Engl., 29, 535 (1990); D. Villemin, B. Labiad, Y. Ouhilal, Chemistry & Industry, 607 (1989); A.B. Alloum, B. Labiad, and D. Villemin, J. Chem. Soc. Chem. Commun., 386 (1989), E. Bouhlel, P. Laszlo, M. Levart, M. Th. Montaufier, G.P. Singh, Tetrahedron Lett., 34, 1123 (1993); A. Chakrabarty, M.M. Sharma, Reactive Polymers, 18, 107 (1992); A. Chakrabarty, M.M. Sharma, Reactive Polymers, 17, 331 (1992); M.M. Sharma, Reactive & Functional Polymers, 32, 93 (1997)]. 4,4-Diaminodiphenylmethanes and its derivatives are chain extenders and curatives. Sterically hindered diamines like orthoalkylated 4,4'-methylene-dianilines obtained from dialkylanilines have been used as amine chain extenders along with polyols in the manufacture of polyurethanes (reaction injection moulding applications). This can also be used in the preparation of epoxy resins. These epoxy resins are curing agents. Curing agents determine the type of chemical bonds formed and the degree of cross linking which occurs with the epoxy resin, which in turn affects the chemical resistance, electrical properties and heat resistance of the cured resin. Aromatic diamines have moderate heat resistance and good thermal resistance [P.O. Nielson "Properties of epoxy resins, hardners and modifiers", Adhesives Age, 42 (1982); D.J. Glover, J.V. Duffy and B. Hartmann, J. Polym. Sci. Polym. Chem. Ed., 26, 79 (1988)]. Conventional method of synthesis of diaminodiphenylmethane derivatives involves condensation of aniline with formaldehyde in presence of equimolar amounts of cone. HC1 according to the procedure reported by J.T. Scanlan [J.T. Scanlan, J. Am. Chem. Soc., 57, 890 (1935)]. Apart from the repeated usage of concentrated mineral acid catalyst, the synthesis route is cumbersome involving sleam distillation and undcsired products due to polymerization. To maintain the environmental integrity, attempts are being made all over the world to substitute conventional acid based catalysts by suitable efficient environmentally benign solid acids like zeolites, mixed oxides, synthetic and natural clays and related materials. The present invention employs an eco-friendly catalyst. The present process relates to the synthesis of 4,4'-diaminodiphenyl-methane (1) and its derivatives by the condensation of aniline with formaldehyde in the presence of natural clays, kaolins. The salient features of the process are (i) Usage of eco-friendly catalyst and hence cost effective (ii) Efficient catalyst with good turn over lesser reaction period energy saving (iii) Simpler work-up procedure (iv) Catalyst is reusable. An object of the present invention is to provide an improved process for the synthesis of diaminodiphenylmethanes under eco-friendly conditions. Accordingly, the present invention provides an improved process for the synthesis of 4,4'-diaminodiphenylmethanes and its substituted derivatives which comprises, (i) adding aromatic amino compound to a mixture of eco-friendly catalyst such as noticed days & kaoluins and water in a ratio rangeing from 1:100 to 1:500 followed by addition of formaldehyde and continuing the stirring for a period in the range of 0.5 to 1.0 h, (ii) separating the residue from the reaction mixture by known methods and purifying by conectional technings. In an embodiment of the present invention, the aromatic amino compounds used may be such as aniline, 2,6-dimethylaniline, N,N-dimethylaniline, 3,5-dimethylaniline, 2,3-dimethylaniline, 2-chloroaniline. In another embodiment of the invention, the known methods used for separation of residue may be such as filtration, decantation etc. Purification of crude compound may be effected by recrystallisation. The catalyst used may be clay such as Kaolin (1:1 sheet silicate), Bentonite, Attapulgite, Palygorskite, Montmorillonite (2:1 sheet silicates) and laterite. By employing clay catalyst-water as the synthesis media, the process becomes truly eco-friendly and cost effective. Such a system has not been reported so far to the best of our knowledge. The process is extendable to the synthesis of substituted diamino-diphenylmethanes like (a) 3,5,3',5'-tetramethyl,4,4'-diaminodiphenylmethane (2), (b) 2,3,2',3'-tetramethyl,4,4'-diaminodiphenylmethane (3) (c) 4,4'-bis(dimethylamino)diphenylmethane (4) (d) 4,4'-diamino 3,3'-dichlorodiphenylmethane (5) etc. The details of the invention is described in the example given below which is provided by way of illustration only and should not construed to limit the scope of invention. Example 1 Synthesis of 4,4'-diaminodiphenylmethane by the condensation of aniline with formaldehyde using Kaolin catalyst Aniline is added to a kaolin-water slurry (1:100) which is kept vigorously stirred. To this, formaldehyde (40% soln.) is added dropwise and the mixture stirred for half an hour. The residue is filtered out and dissolved in hot water. Alternatively, alcohol can also be used for extracting the product. Kaolin is separated by filtration or centrifugation. Product is crystallised from hot water (Table 1) and analyzed by spectral methods. Example 2 Synthesis of 3,5,3'»5'-tetramethyl,4,4'-diaminodiphenylmethane 2,6-Dimethylaniline is added to a kaolin-water slurry (1:300) which is kept vigorously stirred. To this, formaldehyde (40% soln.) is added dropwise and the mixture is kept stirred for half an hour. The residue is filtered out and dissolved in hot water. Alternatively, alcohol can also be used for extracting the product. Kaolin is separated by filtration or centrifugation. Product is recrystallised from hot water (Table 1). Example 3 Synthesis of 4,4'-bis(dimethylamino)diphenyImethane N,N-dimethylaniline is added to a kaolin-water slurry (1:500) which is kept vigorously stirred. To this, formaldehyde (40% soln.) is added dropwise and the mixture stirred for half an hour. The residue is filtered out and dissolved in hot water. Alternatively, alcohol can also be used for extracting the product. Kaolin is separated by filtration or centrifugation. Product is recrystallised from hot water (Table 1). Table 1. Condensation of aromatic amines with formaldehyde, fonnation of 4,4'-diaminodiphenylmethanes (Table Removed) Amine : formaldehyde = 2:1, ambient temperature The main advantages of the present invention are 1. No use of hydrocarbon solvents. Water is used as solvent. Pollution free process. 2. Kaolin as catalyst instead of mineral acids which are corrosive. Ecofriendly. 3. Catalyst is efficient and abundantly available. Cost-effective. 4. No steam distillation is required during work-up unlike the conventional procedure. Time/energy saving. 5. Conversion is 100% 6. No polymerization 7. No formation of undesired products Claim: 1. An improved process for the synthesis of 4,4'-diaminodiphenymlethane and its A substituted derivatives which comprises: i) adding aromatic amino compound to a mixture of eco-friendly catalysts such as natural clays and kaolins and water in a ratio ranging from 1:100 to 1:500 followed by addition of formaldehyde and continuing the stirring for a period in the range of 0.5 to 1.0 h, and ii) separating the residue obtained from step (i) from the reaction mixture by known methods and purifying by conventional techniques. 2. An improved process as claimed in claim 1, wherein the clays belong to the kaolinite variety, bentonite, attapulgite, playgorspites, mountmorillonite. 3. An improved process as claimed in claims 1, wherein the aromatic amino compounds used is such as aniline, 2,6-dimethylaniline, N,N-dimethyl-aniline, 3,5- dimethylaniline, 2-chloroaniline. 4. An improved process for the synthesis 4,4'-diaminodiphenylmethane and its substituted derivatives substantially as herein described with reference to the examples 1 to 3.

Full Text

This invention relates to an improved process for the synthesis of 4,4-diaminodiphenylmethanes and its substituted derivatives.
The process is simple, speedy, selective and eco-friendly with 100% conversion. Work up procedure requires extraction of the product into hot water from which it is recrystallised.
It is well known that clays act as efficient catalysts in acid/base promoted reactions in organic synthesis [J.M. Adams, Applied Clay Science, 2, 309 (1987); P. Laszlo, Ace. Chem. Res., 19, 121 (1986); P. Laszlo, Science, 235, 1473 (1987); A. Cornells, P. Laszlo, Aldrichimica Acta, 21, 97 (1988)]. In particular, acid catalysed reactions promoted by mineral acids or Lewis acids constitute a major area of industrial organic chemistry. Efforts have been made in the past to effectively substitute these toxic corrosive chemicals by mild but efficient solid-acid catalysts. [G.J. Ross, Clays. Clay Miner., 17, 347 (1967); J.H. Clarke et al., J. Chem. Soc., Chem. Com., 1353 (1989); Tennakon et al., J.C.S. Dalton, 2207 (1974); SJ. Barlow, T.W. Bastock, J.H. Clark, S.R. Cullen, J. Chem. Soc. Perkin II, 411 (1994); J. Tateiwa, T. Nishimura, H. Horiuchi, S. Uemura, J. Chem. Soc. perkin I, 3367 (1994); C. Collet, A. Delville, P. Laszlo, Angew. Chem. Int. Ed. Engl., 29, 535 (1990); D. Villemin, B. Labiad, Y. Ouhilal, Chemistry & Industry, 607 (1989); A.B. Alloum, B. Labiad, and D. Villemin, J. Chem. Soc. Chem. Commun., 386 (1989), E. Bouhlel, P. Laszlo, M. Levart, M. Th. Montaufier, G.P. Singh, Tetrahedron Lett., 34, 1123 (1993); A.

Chakrabarty, M.M. Sharma, Reactive Polymers, 18, 107 (1992); A. Chakrabarty, M.M. Sharma, Reactive Polymers, 17, 331 (1992); M.M. Sharma, Reactive & Functional Polymers, 32, 93 (1997)].
4,4-Diaminodiphenylmethanes and its derivatives are chain extenders and curatives. Sterically hindered diamines like orthoalkylated 4,4'-methylene-dianilines obtained from dialkylanilines have been used as amine chain extenders along with polyols in the manufacture of polyurethanes (reaction injection moulding applications). This can also be used in the preparation of epoxy resins. These epoxy resins are curing agents. Curing agents determine the type of chemical bonds formed and the degree of cross linking which occurs with the epoxy resin, which in turn affects the chemical resistance, electrical properties and heat resistance of the cured resin. Aromatic diamines have moderate heat resistance and good thermal resistance [P.O. Nielson "Properties of epoxy resins, hardners and modifiers", Adhesives Age, 42 (1982); D.J. Glover, J.V. Duffy and B. Hartmann, J. Polym. Sci. Polym. Chem. Ed., 26, 79 (1988)].
Conventional method of synthesis of diaminodiphenylmethane derivatives involves condensation of aniline with formaldehyde in presence of equimolar amounts of cone. HC1 according to the procedure reported by J.T. Scanlan [J.T. Scanlan, J. Am. Chem. Soc., 57, 890 (1935)].
Apart from the repeated usage of concentrated mineral acid catalyst, the synthesis route is cumbersome involving sleam distillation and undcsired products due to polymerization.
To maintain the environmental integrity, attempts are being made all over the world to substitute conventional acid based catalysts by suitable efficient environmentally benign solid acids like zeolites, mixed oxides, synthetic and natural clays and related materials. The present invention employs an eco-friendly catalyst.
The present process relates to the synthesis of 4,4'-diaminodiphenyl-methane (1) and its derivatives by the condensation of aniline with formaldehyde in the presence of natural clays, kaolins.
The salient features of the process are
(i) Usage of eco-friendly catalyst and hence cost effective (ii) Efficient catalyst with good turn over
lesser reaction period energy saving
(iii) Simpler work-up procedure (iv) Catalyst is reusable.
An object of the present invention is to provide an improved process for the synthesis of diaminodiphenylmethanes under eco-friendly conditions.
Accordingly, the present invention provides an improved process for the synthesis of 4,4'-diaminodiphenylmethanes and its substituted derivatives which comprises,
(i) adding aromatic amino compound to a mixture of eco-friendly catalyst such as noticed days & kaoluins and water in a ratio rangeing from 1:100 to 1:500 followed by addition of formaldehyde and continuing the stirring for

a period in the range of 0.5 to 1.0 h,
(ii) separating the residue from the reaction mixture by known methods and purifying by conectional technings.
In an embodiment of the present invention, the aromatic amino compounds used may be such as aniline, 2,6-dimethylaniline, N,N-dimethylaniline, 3,5-dimethylaniline, 2,3-dimethylaniline, 2-chloroaniline.
In another embodiment of the invention, the known methods used for separation of residue may be such as filtration, decantation etc. Purification of crude compound may be effected by recrystallisation.
The catalyst used may be clay such as Kaolin (1:1 sheet silicate), Bentonite, Attapulgite, Palygorskite, Montmorillonite (2:1 sheet silicates) and laterite.
By employing clay catalyst-water as the synthesis media, the process becomes truly eco-friendly and cost effective. Such a system has not been reported so far to the best of our knowledge.
The process is extendable to the synthesis of substituted diamino-diphenylmethanes like
(a) 3,5,3',5'-tetramethyl,4,4'-diaminodiphenylmethane (2),
(b) 2,3,2',3'-tetramethyl,4,4'-diaminodiphenylmethane (3)
(c) 4,4'-bis(dimethylamino)diphenylmethane (4)
(d) 4,4'-diamino 3,3'-dichlorodiphenylmethane (5) etc.
The details of the invention is described in the example given below which is provided by way of illustration only and should not construed to limit the scope of invention.
Example 1
Synthesis of 4,4'-diaminodiphenylmethane by the condensation of aniline with formaldehyde using Kaolin catalyst
Aniline is added to a kaolin-water slurry (1:100) which is kept vigorously stirred. To this, formaldehyde (40% soln.) is added dropwise and the mixture stirred for half an hour. The residue is filtered out and dissolved in hot water. Alternatively, alcohol can also be used for extracting the product. Kaolin is
separated by filtration or centrifugation. Product is crystallised from hot water (Table 1) and analyzed by spectral methods.
Example 2
Synthesis of 3,5,3'»5'-tetramethyl,4,4'-diaminodiphenylmethane
2,6-Dimethylaniline is added to a kaolin-water slurry (1:300) which is kept vigorously stirred. To this, formaldehyde (40% soln.) is added dropwise and the mixture is kept stirred for half an hour. The residue is filtered out and dissolved in hot water. Alternatively, alcohol can also be used for extracting the product. Kaolin is separated by filtration or centrifugation. Product is recrystallised from hot water (Table 1). Example 3 Synthesis of 4,4'-bis(dimethylamino)diphenyImethane
N,N-dimethylaniline is added to a kaolin-water slurry (1:500) which is kept vigorously stirred. To this, formaldehyde (40% soln.) is added dropwise and the mixture stirred for half an hour. The residue is filtered out and dissolved in hot water. Alternatively, alcohol can also be used for extracting the product. Kaolin is separated by filtration or centrifugation. Product is recrystallised from hot water (Table 1).
Table 1. Condensation of aromatic amines with formaldehyde, fonnation of 4,4'-diaminodiphenylmethanes

(Table Removed)
Amine : formaldehyde = 2:1, ambient temperature
The main advantages of the present invention are
1. No use of hydrocarbon solvents. Water is used as solvent. Pollution free
process.
2. Kaolin as catalyst instead of mineral acids which are corrosive.
Ecofriendly.
3. Catalyst is efficient and abundantly available. Cost-effective.
4. No steam distillation is required during work-up unlike the conventional
procedure. Time/energy saving.
5. Conversion is 100%
6. No polymerization
7. No formation of undesired products

Claim:

1. An improved process for the synthesis of 4,4'-diaminodiphenymlethane and its
A
substituted derivatives which comprises: i) adding aromatic amino compound to a mixture of eco-friendly catalysts such as
natural clays and kaolins and water in a ratio ranging from 1:100 to 1:500
followed by addition of formaldehyde and continuing the stirring for a period in
the range of 0.5 to 1.0 h, and ii) separating the residue obtained from step (i) from the reaction mixture by known
methods and purifying by conventional techniques.
2. An improved process as claimed in claim 1, wherein the clays belong to the kaolinite
variety, bentonite, attapulgite, playgorspites, mountmorillonite.
3. An improved process as claimed in claims 1, wherein the aromatic amino compounds
used is such as aniline, 2,6-dimethylaniline, N,N-dimethyl-aniline, 3,5-
dimethylaniline, 2-chloroaniline.
4. An improved process for the synthesis 4,4'-diaminodiphenylmethane and its substituted derivatives substantially as herein described with reference to the examples 1 to 3.

Documents:

1123-del-1998-abstract.pdf

1123-del-1998-claims.pdf

1123-del-1998-correspondence-others.pdf

1123-del-1998-correspondence-po.pdf

1123-del-1998-description (complete).pdf

1123-del-1998-form-1.pdf

1123-del-1998-form-19.pdf

1123-del-1998-form-2.pdf

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Patent Number

216251

Indian Patent Application Number

1123/DEL/1998

PG Journal Number

13/2008

Publication Date

28-Mar-2008

Grant Date

11-Mar-2008

Date of Filing

27-Apr-1998

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	RUGMINI SUKUMAR	REGIONAL RESEARCH LABORATORY (CSIR), TRIVANDRUM-695 019.
2	KUZHUNELLIL RAGHAVAN PILLAI SABU	REGIONAL RESEARCH LABORATORY (CSIR), TRIVANDRUM-695 019.
3	MALATHY LALITHAMBIKA	REGIONAL RESEARCH LABORATORY (CSIR), TRIVANDRUM-695 019.
4	DAMODARAN BAHULAYAN	REGIONAL RESEARCH LABORATORY (CSIR), TRIVANDRUM-695 019.

PCT International Classification Number

C07C

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA