clay catalysts in organic synthesis

8/3/2019 Clay Catalysts in Organic Synthesis

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Presentation for Internal Project Review

byDr. B.Vijayakumar

Department of ChemistryVel Tech High Tech Dr.Rangarajan Dr.Sakunthala Engineering College

Avadi, Chennai-600 062.

Studies on Synthesis of Organic Compoundshaving Commercial Application by Green

Chemical Methods

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Description of the project:

In the proposed project, novel methods are to be developed to obtain

industrially important products such as -damascone, quinoline

derivatives, arenofurans, benzyl nicotinate, etc. For example,

esterification of phenols with sterically hindered or long chain alcohols by

conventional methods is difficult. This can be achieved in presence of

eco-friendly catalysts, particularly clays, in presence of solvents or under

solvent-free conditions.

In the present proposal, Indian clays will be modified systematically using

dilute solutions of mineral and/or organic acids, and metal salts at

different temperatures and time intervals. Further, several ion exchanged

and clay supported catalysts will be prepared using various reagents such

as heteropoly acids, metal salts, etc. to obtain them in desired acidity.

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Modification of clays and their applications

Cation Exchanged Clays(Brnsted acid Catalysts)

Pillared Clays(Lewis acid Catalysts)

Acid Activated Clays(Both Lewis & Brnsted)

Surfactant Modified Clay

(Adsorbents)

Clay supported Reagents(Redox catalysts)

Natural clay

Vijayakumar, B. Clay Catalysts in Organic Synthesis (Synlett Spotlight 81) Synlett

2, 2004, 388-389.

Clays are layered hydrous aluminosilicates composed of tetrahedral silicate

and octahedral aluminate sheets.

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Simple representation of clay

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WATERMOLECULESANDCATIONS

Smectite (2:1)

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Advantages of clay catalysts

Naturally available Cheap/Economic

Easy to modify

Easy to handle

Possess both Lewis and Brnstedacidity

Acidity can be controlled

Reusable

Eco-friendly

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1. to prepare indigenous smectite clays (acid treated, exchanged, and

supported) with different acidities.

2. to make a systematic study of the relationship between properties of

catalysts and their catalytic activities.

3. to explore and optimize conditions to synthesize organic compounds of

commercial importance.

4.to study the catalytic activities of the samples prepared for the

synthesis of valuable products such as esters, quinolines, imidazole

derivatives, arenofurans, quinazolinones, damascones, etc.

Objectives

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Preparation of cation exchanged clays

+ Stirred at RT

Washed with distilled water

Dried at 100o

C

Clay Mn+-ion solution Mn+-exchangedcla sus ension

Mn+

-exchangedclay

Mn+

-exchanged claycatalyst

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Stirred

+ at 90- 95oC

Washed with distilled water

Dried at 100

o

C

Clay Mineral acid

(Dil. Solution)

Acid-clay

sus ension

Acid activated clayAcid activatedclay catalyst

Preparation of acid activated clays

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+ Stirred at RT

Solvent was removed under vacuum

Dried at 100oC

Clay Inorganic salt in

solventClay-inorganic

salt sus ension

Inorganicsalt/clay

Inorganic

salt/claycatalyst

Preparation of supported clay catalysts

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(i) Synthesis of 4-substituted-2-(1-(phenylsulfonyl)-1H-pyrrolo[2,3-b]pyridin-3-yl)quinolines:

7-azaindole-3-carboxaldehyde

1 can be obtained from 7-

azaindole in two steps.

Treatment of1 with

substituted aniline 2 in

presence of clay catalysts

would form an N-aryl aldimine

intermediate, which

subsequently undergoes

[4+2]-cycloaddition with

substituted alkyne 3 followed

by aerobic dehydrogenation to

obtain quinoline derivatives.

N

N

O

SO2Ph

+ H2N

R

Catalyst

SolventR'

N

N

N

SO2Ph

R'

R

1

2

4

3

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(ii) Synthesis of new heteroaryl substituted quinolines:

+ +NC CN

OH

1-NaphtholN

CHO

OCH3

R

Malononitrile

NOCH3

R

O

CN

NH2

Clay catalysts

Substituted 2-methoxy quinoline-3-carbaldehyde

Heteroaryl substituted quinolines and their derivatives exhibit

pharmacological activity such as aldosterone synthase (CYP11B2) inhibitors,

neurokinin (NK)-2/NK-3 receptor ligands, etc.,22-01-2012


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(iii) Synthesis of tetrasubstituted imidazoles:

+ +R' NH2RCHO N

N

Ph

Ph

RR'

+

OO

Ph Ph

Catalyst

CH3COO-NH4

+

Functionalized imidazoles consist of an important class of pharmacologically

active compounds that have a variety of interesting properties. Benzil,

aldehyde, amine and ammonium acetate are reacted in presence of a

catalyst to form a tetrasubstituted imidazole.

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(iv) Synthesis of arenofurans:

+

NO2

R2

R1

Clay catalysts

OR2

R1

OH

RR

Arenofurans are present in many natural products that show fungicidal,

antimicrobial, insecticidal, antiproliferative, cytotoxic and antioxidant

properties. Phenol or substituted phenol or naphthol can be reacted

with nitroalkene in presence of clay catalyst to form corresponding

arenofurans by a cyclization reaction.

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(v) Synthesis of 4(3H)-quinazolinones:

H2N

O

H2N

Anthranilamide

+ R-CHO

Metal salt/Clay N

NH

O

R

Quinazolinone derivatives have drawn much attention due to their broad

range of pharmacological activities, such as anticancer, antiinflammatory,

anticonvulsant and antidituric activities. Anthranilamide, aldehyde and a

metal salt supported clay catalyst will be reacted in refluxing solvent to

obtain the corresponding 4(3H)-quinazolinones.

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Any literature survey done? If so, please give details:

There are reports on clays as catalysts in organic synthesis in the

literature. An important list of references is as follows.

[1] Rothenberg, G., Catalysis: Concepts and Green Applications, WILEY-VCH

Verlag GmbH & Co. KGaA, Weinheim, 2008.

[2] a) McCabe, R.W., In Inorganic Materials: Clay Chemistry, Bruce, D.W.

and O'Hare, D., Eds.; John Wiley and Sons: Chichester, 1992, 295-351.

b) Smith, K., " Solid Support and Catalyst in Organic Synthesis" Ellis

Harwood Chichester 1992. c) Augustine, R. L., "Heterogeneous Catalysis

for the Synthetic Chemist" Marcel & Dekker 1996.

[3] Balogh, M. and Laszlo, P., Organic Chemistry Using Clays, Springer:

Berlin, 1993.

[4] a) Vijayakumar, B., Clay Catalysts in Organic Synthesis, Synlett

2004,2,388. b) Nagendrappa, G., Appl. Clay Sci. 2011, 53, 106.

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What is the state of the art in the area in which you proposeto take up the project:

Most of the currently conducted industrial reactions involvingpharmaceuticals, perfumes and petrochemicals make use of metals,

metal salts, metal oxides, mineral acids, metal hydroxides, microporous

zeolites, ion-exchange resins, etc.

Many reactions are performed under harsh conditions with toxic and

expensive reagents.

The organic compounds to be synthesised in the project have been

prepared using expensive and toxic reagents and are valuable products.

For example, -damascone is an important compound in perfume

industry.

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Methodology to execute the project:

1. Procurement of indigenous clays and preparing acid treated, supported,

and various cation-exchanged clays,

2. Characterisation of the catalyst samples by XRD, XRF, TGA, DTA, FTIR-

DRIFTS, TPD-NH3, and BET surface area measurements,

3. Utilisation of these clay catalysts (catalytic activity) for carrying out

organic transformations,

4. Optimisation of the reaction conditions for obtaining the value added

products mentioned in the project in high yields, and

5. Synthesis of the organic compounds of interest in perfumes,

pharmaceuticals, biologically activity, etc. and characterising the organic

compounds by IR, HRMS and NMR.

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9. Expected outcome of the project (Utility or application):

Outcome of the project may evince some interest from industries, which

are presently using conventional acid catalysts such as H2SO4 and HCl. An

associated socio-economic factor would be the indirect benefit, the clay-

mining activity would derive, which possibly might lead to the cost

reduction and better utilisation of industrial resources. Further, the

project has commercial application and/or patentability. The catalysts

prepared in the proposed project can be reused and the organic

compounds are used in perfumery, cosmetics, and pharmaceuticals. The

main advantage of this method is elimination of pollutant organic solvents

and the environmentally friendly character.

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Thank you for your kind attention

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clay catalysts in organic synthesis

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