Synthesis and Properties of Furan-Based Dyes and Colorants

APPLICATION OF
FURAN & ITS DERIVATIVE
1

PROPERTIES
 Furan is a heterocyclic organic compound,
consisting of a five-membered aromatic ring with
four carbon atoms and one oxygen. The class of
compounds containing such rings are also referred
to as furans.
 Furan is a colorless, flammable,
highly volatile liquid with a boiling point close to
room temperature. It is soluble in common organic
solvents, including alcohol, ether, and acetone, and
is slightly soluble in water.It is toxic and may
be carcinogenic in humans. Furan is used as a
starting point to other specialty chemicals.
2

DIARYL FURAN SERIES
 The diaryl furan series, more specifically the 2,5-bis
aryl furans, especially in which the amino group is
para to the furan bond are useful as brighteners
and as intermediates for dyes and pigments.
 2,5-bis(para-amino phenyl) furan is a valuable
intermediate from which dyes, pigments,
brighteners, etc may be prepared.
 The acyl derivatives of this diamine, as well as its
sulfonated derivatives possess fluorescence and
can be used as brighteners.
3

2,5-BIS (PARA AMINO PHENYL) FURAN
4

 The sulfonated derivatives are particularly useful in
this respect because they are water soluble and
have affinity for cellulosic materials.
 The N,N-dialkyl derivatives have less affinity for
cellulosic materials but can be used to whiten
materials such as wool, nylon and acetate.
 Also, the amino groups of this furan can be
diazotized and can be coupled to give azoic dyes
and pigments. The sulfonated derivatives can be
similarly treated to produce azo dyes.
5

 Sulfonation of this furan gives furan disulfonic acid
and this can be further acylated to obtain water
soluble brighteners.
 The 2,5-bis(para-amino phenyl) furan and its
sulfonic acid derivatives can be diazotized and
coupled with phenols, naphthols,
aminophenols,aminonaphthols,naphthol sulfonic
acids, aminonaphthol sulfonic acids,etc.
6

DIARYL FURANS WITH METALLIZABLE GROUPS
 The diaminodiaryl furans containing metallizable groups
ortho to the amino group are important in the dyestuff
industry.
 The metallizable groups include hydroxyl, carbonyl,
halogen, alkoxy,etc.
 When these groups are present the azo dyes obtained
can be converted to metal complexes.
 These complexes are useful for the dyeing of cotton and
rayon in attractive shades and have much better light
fastness than the unmetallized dyes. The most stable
and useful complexes are those derived from dyes in
which the coupling component also contains a
metallizable group ortho to the azo linkage.
 Copper is the most useful metal, but other metals such
as nickel, cobalt, chromium can be used.
7

NAPHTHALENE SERIES
 Compounds of the naphthalene series are also
important in the dyestuff industry.
 For example, 2,5-bis (para amino naphthyl) furans.
8

 By using acetyl derivatives of compounds such as
1-amino-2-ethoxy naphthalene, 1-amino-2,6-
dimethoxy naphthalene, 1-amino-2-naphthol, 1-
amino-2-naphthoic acid and 1-amino-2-naphthoxy
acetic acid, new intermediates are obtained which
are useful for the preparation of metallized dyes
and pigments.
 These compounds can also be sulfonated, usually
more readily than corresponding benzene
derivatives.
9

BRIGHTENERS
 Brighteners containing basic substituents, are
useful for non-cellulosic material such as wool,
nylon as well as for incorporation in plastics, can be
prepared by alkylating 2,5-bis (aminoaryl) furans,
using alkylating agents such as dialkyl sulfates or
alkyl halides.
 The properties of the products depends on the size
of the alkyl group, since larger the alkyl group
greater is the solubility expected in plastics.
10

APPLICATION OF FURFURAL & FURFURYL
ALCOHOL
Furfural
Furfuryl
alcohol
11

 Furfural is used to make other furan chemicals, such as
furoic acid, via oxidation.
 and furan itself via palladium catalyzed vapor phase
decarbonylation.
 Furfural is also an important chemical solvent.
 Furfural is an important renewable, non-petroleum
based, chemical feedstock.
 Hydrogenation of furfural provides furfural
alcohol (FA), which is a useful chemical intermediate
and which may be further hydrogenated to
tetrahydrofurfuryl alcohol (THFA).
13

 The papers in books contain hemicelluloses which are
the sources of furfural. Furfural is one of the many
chemicals that contribute to the aroma of books. The
gradual degradation of the complex mixture of volatile
chemicals within paper, used in the manufacture of
books, produces the aroma of books which is associated
with furfural.
 Furfural is often used as an agent for decolorizing crude
wood resin. It is used widely as a solvent in petroleum
refining, lubricants and specialist adhesives.
 Furfural was used as a fuel dye for all heating fuel for tax
purposes in Finland before being replaced in 31.8.2003
by Solvent Yellow 124 due to EU legislation.
14

 The largest volume of furfuryl alcohol is in the
manufacturing of dark, thermosetting resins which have
excellent resistance to corrosive chemicals, acids, bases,
alkalies and solvents.
 Furfuryl alcohol is solvent for phenolic resins and dyes .
 It is also used as dispersant for dyes which are difficult to
dissolve.
15

DYE SENSITIZED SOLAR CELLS
 A dye-sensitized solar cell (DSSC) is a low-cost solar
cell belonging to the group of thin film solar cells.
 It is based on a semiconductor formed between a photo-
sensitized anode and an electrolyte a photo
electrochemical system.
 Sunlight enters the cell through the transparent SnO2:F
top contact, striking the dye on the surface of the TiO2.
Photons striking the dye with enough energy to be
absorbed create an excited state of the dye, from which
an electron can be "injected" directly into the conduction
band of the TiO2. From there it moves by diffusion (as a
result of an electron concentration gradient )to the
clear anode on top. 17

 Meanwhile, the dye molecule has lost an electron and the
molecule will decompose if another electron is not
provided. The dye strips one from iodide in electrolyte
below the TiO2, oxidizing it into triiodide.
 This reaction occurs quite quickly compared to the time
that it takes for the injected electron to recombine with
the oxidized dye molecule, preventing this recombination
reaction that would effectively short-circuit the solar cell.
 The triiodide then recovers its missing electron by
mechanically diffusing to the bottom of the cell, where
the counter electrode re-introduces the electrons after
flowing through the external circuit.
18

 Although the dye is highly efficient at converting
absorbed photons into free electrons in the TiO2,
only photons absorbed by the dye ultimately
produce current.
 The rate of photon absorption depends upon the
absorption spectrum of the sensitized TiO2 layer
and upon the solar flux spectrum.
 The overlap between these two spectra determines
the maximum possible photocurrent.
 Typically used dye molecules generally have poorer
absorption in the red part of the spectrum
compared to silicon, which means that fewer of the
photons in sunlight are usable for current
generation. 19

 New metal-free dyes with a furan moiety in the
conjugated spacer between the aryl amine donor
and the 2-cyanoacrylic acid acceptor have been
synthesized, and high efficiency dye-sensitized
solar cells were fabricated using these molecules
as light-harvesting sensitizers.
20

Synthesis of styryl colorants containing heterocyclic
linker or
acceptor units
• Heterocyclic styryl colorants have been in demand in high
value-added products such as
sensitizers in optical recording materials, photography, laser
dyes and fluorescent probes.
These colorants are also suitably used for application in non-
linear optics
(NLO).
Nonlinear optics is the branch of optics, which deals with the
phenomena that occurs as a consequence of modification of
the optical properties of material with the
incident light wave.
21

•In the last few years, the interest in the design and
synthesis of novel materials organic materials with
nonlinear optical (NLO) properties has grown considerably
because of their potential applications in photonic
technologies.
•The basic structure of these molecules consists of a donor
(D) and an acceptor (A) linked via a conjugation bridge or
linker.
Synthesis of styryl colorants containing heterocyclic
linker or
acceptor units
22

•Aromatic rings as linkers are known to enhance thermal
stability.
•Replacing simple aromatic rings with more easily
delocalizable 5-membered heteroaromatic rings such as
furan
• results in an enhanced molecular hyperpolarizability.
•This could possibly be due to more easily delocalizable π-
orbitals in 5-membered rings than in benzene.
Styryl colorants :
23

Synthesis of heterocyclic bridged styryl dyes
•A variety of heterocyclic bridged novel chromophores were
synthesized by condensation of different donor aldehydes
with furan & acetonitrile based acceptor moieties by refluxing
in ethanol using catalytic amount of piperidine.
•The acceptor heterocyclic bridged moiety and were
synthesized by condensation of 5-methylfuran-2-
carbaldehyde with 4-nitrophenylacetonitrile in ethanolic
media using piperidine as a base
24

Synthesis of furan based acceptor unit
25

26

27

28

29

Thermal stability of Colorants :
The higher value of thermal stability makes these
molecules suitable for high-technological application such
as non-linear optics.
30

 The furanyl cyano acrylic acid anchor is employed
for all the sensitizers, aiming to increase the
influence of the cyano acrylic acid acceptor group.
 Replacing the anchoring phenyl ring of DPP07 with
the furan ring of DPP13 provides a 20 nm red shift
in the charge transfer (CT) light absorption band
 in combination with increased intensity of the CT
band compared to the higher energy band.
Blue-Coloured Highly Efficient Dye-Sensitized Solar
Cells
31

 Dyes with different conjugated linkers such as furan,
bifuran, selenophene have been prepared in
combination with the dihexyloxy-substituted
triphenylamine donor and the cyanoacrylic acid
acceptor.
 In conjunction with an acetonitrile based electrolyte
and a solvent free ionic liquid electrolyte, these dyes
exhibit 6.88-7.77% and 6.39-7.00% efficiencies
respectively. Thus furan can be employed as building
blocks of sensitizers in stable solar cells.
Dye-Sensitized Solar Cells Based on Organic
Sensitizers with Different
Conjugated Linkers: Furan, Bifuran,
33

FURAN DERIVATIVES USED AS
FUNGICIDES
34

 Furan-3-carboxamides are used as fungicides.
 These compounds are effective in many applications but
are not effective against all forms of fungi which attacks
seeds.
 Improvements are required in seed dressing
compositions.
35

 The term furan-3-carboxamide means the compounds of
structural formula
 Where R is hydrogen, methyl or other alkyl, acyl or aryl
groups
 R’ is hydrogen, cycloalkyl, benzyl, phenyl or substituted
phenyl etc.
 The preferred furan-3-carboxamides are the
carboxanilides where X is methyl and Y, Z are from the
group consisting H and methyl
36

 E.g. 2-methylfuran-3-carboxanilide
2,5-dimethylfuran-3-carboxanilide
2,4,5-trimethylfuran-3-carboxanilide
 These compositions are used as fungicides and is useful
when applied to seeds.
 For control of phytopathogenic fungi on seed, materials
containing mercury are used. This possess
disadvantages of toxicity to warm blooded animals.
 However, the above fungicides in the form seed dressing
are less toxic than mercury containing compounds and
therefore are suitable for agriculture, gardening, etc.
37

 These compounds can be used together with one or
more additional pesticides materials such as
organochlorine compounds such as lindane or repellants
such as benzathrone, anthraquinone, thioanthraquinone,
etc. to protect the seeds against pests such as insects
and birds.
38

EXAMPLE:-
 Effectiveness against snow mould on rye
 Naturally infected rye seed was treated in the
greenhouse with compositions referred in table given
below and planted out in garden soil in wooden boxes.
The level of infection was determined from the
occurrence of fungi in the untreated control.
39

 Effectiveness against Bunton Wheat Tilletia caries
 When seed inoculated with spores was treated and
planted in open land. Before the harvest the ears infected
with bunt were counted.
41

MEDICINAL SIGNIFICANCE OF FURAN DERIVATIVES
42

• Furan is a planer five-member heterocyclic ring with 4C
and 1O atom and in ring O is present in 1st positions.
• The furan ring is a constituent of several important
natural products, including furanoflavonoid,
furanolactones, fura-nocoumarins and many natural
terpenoids.
• Being a non polar aromatic compound and presence of
the ether oxygen which adds polarity as well as the
potential for hydrogen bonding, it improves
pharmacokinetic characteristics of lead molecules and
thus used as a remedy to optimize solubility and
bioavailability parameters of proposed poorly soluble
lead molecules.
43

• Furan derivatives have occupied a unique place in the field
of medicinal chemistry.
• The incorporation of the furan nucleus is an important
synthetic strategy in drug discovery.
44

MEDICINAL CHEMISTRY
 Medicinal chemistry is the discipline which
determines the influence of chemical structure on
biological activity and the practice of medicinal
chemistry involves the organic synthesis of new
compound based largely on the modification of
structure and identifying their bio-logical activity.
 Medicinal chemistry concerns with the discovery,
development, interpretation and the identification of
mechanism of action of biologically active
compounds at the molecular level. Every drug has
specific target in the body.
45

• These targets or receptors are believed to be
associated with disease and disorder.
• The newly discovered compounds interact with these
receptors to show their potentiality to treat the
disease or disorder.
46

STRUCTURE AND PHARMACOLOGICAL
ACTIVITIES
 The electrophilic substitution reactions of furan take
place prefer-ably in 2-position.
 On account of its high reactivity very mild reagents
are required as compared to other compounds.
 Compounds containing the furan ring are generally
excellent solvents.
 Some are miscible with both water and with
hexane.
47

• Presence of the ether oxygen adds polarity as well as
potential for hydrogen bonding.
• Compound containing the furan or tetra hydro furan
ring are biologically active and are present in a number
of pharmaceutical products.
• Furfurylamine is an intermediate in the diuretic,
furosemide.
• Tetra hydro furfurylamine may also have
pharmaceutical applications.
• 5-(Dimethyl amine methyl) furfuryl alcohol is an
intermediate in the preparation of ranitidine, which is
used for treating ulcers.
48

• 2-Acetylfuran, prepared from acetic anhydride and
furan is an intermediate in the synthesis of
cefuroxime, a penicillin derivative.
• 2-Furoic acid is prepared by the oxidation of furfural.
Both furoic acid and furoyl chloride are used as
pharmaceutical intermediates.
49

FURAN AS A VERSATILE REACTANT
Reactivity of furan-
 One attribute that makes furan such a useful
building block is its ability to undergo a wide range
of reactions. Because furan can serve as an
immediate precursor to many important
substructures, it has achieved a prominent role in
synthetic chemistry.
 Furan belongs to the family of five-membered
aromatic heterocycles that includes pyrrole and
thiophene.
50

However, it is furan’s ability to undergo reactions
that proceed with dearomatization that has resulted in
its wide application in synthesis.
 Furan can be hydrolyzed under acidic conditions to
give the saturated dicarbonyl derivative.
 Furan is also susceptible to reduction and
oxidation reactions and can provide the unsaturated
dialdehyde 3 by oxidative ring opening with
peracids or similar oxidizing agents.
51

 Other oxidative processes can lead to five-
membered lactones or acetals such as 4 and 5, and
catalytic hydrogenation can lead to tetrahydrofuran
derivatives (6) that are common features in a wide
variety of natural products.
52

SYNTHETICDIVERSITYWITHFURAN
53

 In addition to a nucleophilic aromatic ring or
bis(enol ether), furan can function as an electron-
rich 1,4-diene that is locked into the reactive s-cis
conformation
 Furan participates in Diels–Alder (1) and oxyallyl
cation (2) cycloaddition reactions more readily than
pyrrole or thiophene. Furan’s utility in carbon–
carbon bond-forming reactions considerably
expands its role as a key synthon.
54

Synthesis of New Naphtho[2,3-f]quinoxaline-2,7,12(1H)-
trione and Anthra-9,10-quinone Dyes from Furan-2,3-diones
56

• Furan-2,3-diones (1) have been shown to be very useful synthons for the
preparation of various heterocycles.
• These compounds show typical carbonyl and lactone reactions, depending
on the structures of the nucleophiles involved
• For example, furan-2,3-diones undergo cyclocondensations with 1,2-
diamines to provide the corresponding quinoxalines and aromatic amines
react with furan-2,3-diones to give the corresponding Schiff bases and
pyrrole-2,3-dione derivatives, depending on the reaction times and
temperature
• Furan-2,3-diones (1) can offer many possibilities for the construction of
various heterocyclic dyes including the new naphtho[2,3-f]quinoxaline and
anthra-9,10-quinone derivatives.
• In this work we present new anthra-9,10-quinone (2) and naphtho[2,3-
f]quinoxaline (3) dyes derived from the reactions of some furan-2,3-diones
with 1,2-diaminoanthra-9,10-quinone (1,2-DAAQ) and 1,4-diaminoanthra-
9,10-quinone (1,4-DAAQ), acting as bifunctional nucleophiles
57

• Furan-2,3-diones (1) can offer many possibilities for the construction of
various heterocyclic dyes including the new naphtho[2,3-f]quinoxaline and
anthra-9,10-quinone derivatives
• In this work we present new anthra-9,10-quinone (2) and naphtho[2,3-
f]quinoxaline (3) dyes derived from the reactions of some furan-2,3-diones
with 1,2-diaminoanthra-9,10-quinone (1,2-DAAQ) and 1,4-diaminoanthra-
9,10-quinone (1,4-DAAQ), acting as bifunctional nucleophiles
• Anthra-9,10-quinones and their condensed derivatives with heterocycles
such as indanthrone (Pigment Blue 60, I), anthrapyrimidine (Pigment Yellow
108, II) and Vat Yellow 3 (III) possess brilliant hues and very good fastness
and represent an important group of vat dyes for the textile industry
• In addition to these properties, some anthra-9,10-quinone dyes are widely
used in other fields, such as in medicine and food chemistry [3] and high-
technology systems
58

Pigment Blue 60, Indanthrone
blue
59

Anthrapyrimidine , Pigment Yellow
108
60

Synthesis
• Furan-2,3-dione starting materials 1a-f were prepared . The C5 atom of
compounds 1a-d smoothly reacted with the amino group of 1,2-DAAQ and
1,4-DAAQ to give compounds 2 under mild conditions and in high yields (75-
90%).
• Due to the greater reactivity of the amino group attached to the C2 atom of
1,2-DAAQ, compared with the amino group attached to the C1 atom of 1,2-
DAAQ, 1,2-DAAQ was modified from the amino group attached to C2-
position of 1,2-DAAQ to give 2e.
• On the other hand, the amino group attached to the C2 atom of 1,2-DAAQ
did not react with the C5 atom of 1a at higher temperature, but reacted with
the C3 atom of 1a by forming a Schiff base, which was not isolated
• Through attack of the second amino group on the lactone carbonyl group,
ring opening occurs. The reactions of 1,2-DAAQ with 1b,c,e,f run via the
same reaction pathways to give 3 in nearly quantitative yields of 90-96% in
boiling benzene 62

FURAN: APPLICATIONS IN
PERFUMERY & FOOD SECTORS
65

CARAMELISATION OF FOODS & BEVERAGES
 One of the oldest methods of causing colour and
flavour in food is the heating of sugar and sugar-rich
foods.
 The reactions which occur are responsible for the
caramel-like flavour and the development of a brown
colour.
 The rate of the reaction and the range of the low and
high-molecular-weight reaction products which are
formed can be significantly increased by adding amino
compounds such as amino acids and proteins. In such
a situation the process taking place is the Maillard
reaction.
 Caramelisation requires temperatures >120°C or 9 <
pH < 3. On the other hand, the Maillard reaction
proceeds effectively at temperatures >50°C and is
favoured at pH 4-7, i.e. in the pH range of food.
66

 Depending on the time and temperature, yellow and
brown shades are obtained when solid glucose or
solutions of glucose are heated on their own. The
flavour so produced changes from mild, caramel-
like and sweet to burning bitter. The reaction
causes the release of H +. Thus the pH of the
solution undergoing caramelisation falls with time,
eventually into the slightly sour region of pH 4-5.
 A comparable Maillard reaction between D-glucose
and glycine demonstrates the very marked
acceleration caused by the amino acid; at the same
temperature, a much more intense colour as well as
a greater range of flavour are produced within a few
minutes. 67

MAILLARD REACTION
 Named after French scientist Louis-Camille Maillard
who first described it in 1912.
 The reaction is a form of non-enzymatic browning
which typically proceeds rapidly around 140-165
deg. C. At higher temp, CARAMELIZATION &
subsequently pyrolysis becomes more pronounced.
 This reaction is the basis of Flavouring industry.
 The type of amino acid determines the resulting
flavour.
68

CARAMELISATION REACTION
 Same as that of Maillard reaction, only difference is
that there is no reaction with amino acids instead,
pyrolysis at diff. temp yields diff. types of volatile
chemicals which produce the characteristic caramel
flavour.
70

 HMF (Hydroxymethylfurfural) synthesis:
 A lot of steps are involved like:
Enolization, Dehydration, Aldolisation.
 Mostly caramelization carried out in presence of
molasses which increase rate of reaction.
71

APPLICATIONS OF FURAN DERIVATIVES
 The entire wide range of artificial flavours are
produced via these two reactions & both these
reactions involve furan derivatives like HMF,
Furanones, etc which produce flavour.
72

FURANEOL
 Also called as Strawberry Furanone because of its
rich strawberry aroma.
 Responsible for the odour of fresh pineapples,
tomatoes & buckwheat.
 Used extensively in perfumery industry due to its
strawberry aroma.
73

FURANEOL ALTERNATE SYNTHESIS
74

FURAN AS SOLVENT
 Tetrahydrofuran (THF) is one of the important
solvent used. The compound is classified
as heterocyclic compound, specifically a
cyclic ether. It is a colorless, water-miscible organic
liquid with low viscosity. It is mainly used as a
precursor to polymers. Being polar and having wide
liquid range.It is used as a versatile solvent.

As a Solvent-
 The other main application of THF is as an
industrial solvent for polyvinyl chloride (PVC) and
in varnishes.[4] It is an aprotic solventwith
a dielectric constant of 7.6. It is a moderately polar
solvent and can dissolve a wide range of nonpolar
and polar chemical compounds.[
 THF is water-miscible and can form solid clathrate
hydrate structures with water at low
temperatures.[11]

 In the laboratory, THF is a popular solvent when its
water miscibility is not an issue. It is
more basic than diethyl ether and forms
stronger complexes with Li+, Mg2+, and boranes. It
is a popular solvent for hydroboration reactions and
for organometallic compounds such
as organolithium and Grignard reagents.
 Although similar to diethyl ether, THF is a
stronger base.[13] Thus, while diethyl ether remains
the solvent of choice for some reactions (e.g.,
Grignard reactions).

Potential use and research-
 THF has been explored as a miscible co-solvent in
aqueous solution to aid in the liquefaction and
delignification of plant lignocellulosic biomass for
production of renewable platform chemicals
and sugars as potential precursors to biofuels.[
 Aqueous THF augments the hydrolysis of glycans from
biomass and dissolves the majority of biomass lignin
making it a suitable solvent for biomass pretreatment.

 It is often used in polymer science. For example, it
can be used to dissolve polymers prior to
determining their molecular mass using gel
permeation chromatography. THF dissolves PVC as
well, and thus it is the main ingredient in PVC
adhesives. It can be used to liquefy old PVC
cement and is often used industrially
to degrease metal parts.
 It is used as a component in mobile phases
for reversed-phase liquid chromatography. It has a
greater elution strength than
methanol or acetonitrile.

Polymerisation-
 In the presence of strong acids, THF converts to a
linear polymer called poly(tetramethylene ether)
glycol (PTMEG), also known as polytetramethylene
oxide (PTMO):
 n C4H8O → −(CH2CH2CH2CH2O)n−
This polymer is primarily used to
make elastomeric polyurethane fibers like Spandex.

Synthesis and Properties of Furan-Based Dyes and Colorants

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