16 Green Economy Approach to Develop Bioactive …
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of ions (cation and anion) present in ILs control the stability, chemistry and functionality of ILs at large extent. For example, in different ILs if cations are same but
not anions, the melting points of ILs would be different because of different nature
of anions [11]. It is possible to design the ILs on the demand of synthesis reaction
requirements either by simple changes to the structure of both components (cations
and anions) or by some variations in both ions, hence ILs are referred as designer
solvent or catalyst.
Bronsted acidic ILs are considered as novel, homogeneous catalyst for onepot multi-component reactions in which a series of reactions without any separation of intermediates are performed. 1,3-disulfonic acid imidazolium hydrogen
sulfate {[Dsim]HSO 4 }, a bronsted acidic IL was designed as highly efficient and
reusable catalyst used for the synthesis of hexahydroquinolines (HHQ) via onepot multi-component reaction between dimedone, aromatic aldehydes, β-ketoesters,
and ammonium acetate.{[Dsim]HSO 4 } have three bronsted acidic functional groups
which are capable for dual hydrogen bonding and are responsible for good efficiency
of this IL catalyst. It was observed that treatment of {[Dsim]HSO 4 } with different
arylaldehyde (having either electron-withdrawing groups or electron-donating
groups) provided 88–96% yield of HHQ under controlled reaction conditions with
short time limit (25–45 min) [27].
It has been observed that room temperature ILs generally consist of organic
cations and due to the unsymmetrical structure of these cations, ILs are in liquid
phase even at room temperature. From the past few decades, ILs have become
the topic of interest among the researchers because of their unique properties such
as low volatility/flammability, low vapor pressure, high chemical and electrochemical stability, and tunable structure. Moreover, ILs are considered as green solvents
and catalysts due to their recyclability or regenerability that effectively take part
in designing the various drugs with green chemistry approach. IL [Dsim] HSO 4 has
displayed good restored catalytic activity even after three successive recycle runs with
88–83% product yield [27]. The other reasons for considering the ILs consider as
green solvent or catalyst are ILs exhibit very appealing solvent properties and immiscibility with water or organic solvents due to the strong ionic (Coulomb-) interaction
or hydrogen bonding between the ions present in ILs. They have excellent capability
to being a good reaction medium for chemical synthesis reactions as compared to
organic solvents because ILs are found to be less toxic and high soluble with both
organic and inorganic materials [28]. Organic solvents are led to the high production
of considerable waste during drug synthesis and the synthesized drugs using organic
solvents are costly as well as not eco-friendly. Therefore, ILs are considered as good
alternate for reaction solvent in the synthesis of raw materials, intermediate and drug
substances as ILs are easily recovered and reused. To reduce the toxic and undesired
organic waste in pharmaceutical industries, the use of ILs in the manufacturing of
pharmaceutical was incorporated in 1990s due to excellent physical-chemical properties of ILs and thus ILs began to be considered as environmentally benign compared
to organic solvents. The solvation capability of ILs is decided by anions nature
because anions can form hydrogen bonds with the starting reaction material. The
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of ions (cation and anion) present in ILs control the stability, chemistry and functionality of ILs at large extent. For example, in different ILs if cations are same but
not anions, the melting points of ILs would be different because of different nature
of anions [11]. It is possible to design the ILs on the demand of synthesis reaction
requirements either by simple changes to the structure of both components (cations
and anions) or by some variations in both ions, hence ILs are referred as designer
solvent or catalyst.
Bronsted acidic ILs are considered as novel, homogeneous catalyst for onepot multi-component reactions in which a series of reactions without any separation of intermediates are performed. 1,3-disulfonic acid imidazolium hydrogen
sulfate {[Dsim]HSO 4 }, a bronsted acidic IL was designed as highly efficient and
reusable catalyst used for the synthesis of hexahydroquinolines (HHQ) via onepot multi-component reaction between dimedone, aromatic aldehydes, β-ketoesters,
and ammonium acetate.{[Dsim]HSO 4 } have three bronsted acidic functional groups
which are capable for dual hydrogen bonding and are responsible for good efficiency
of this IL catalyst. It was observed that treatment of {[Dsim]HSO 4 } with different
arylaldehyde (having either electron-withdrawing groups or electron-donating
groups) provided 88–96% yield of HHQ under controlled reaction conditions with
short time limit (25–45 min) [27].
It has been observed that room temperature ILs generally consist of organic
cations and due to the unsymmetrical structure of these cations, ILs are in liquid
phase even at room temperature. From the past few decades, ILs have become
the topic of interest among the researchers because of their unique properties such
as low volatility/flammability, low vapor pressure, high chemical and electrochemical stability, and tunable structure. Moreover, ILs are considered as green solvents
and catalysts due to their recyclability or regenerability that effectively take part
in designing the various drugs with green chemistry approach. IL [Dsim] HSO 4 has
displayed good restored catalytic activity even after three successive recycle runs with
88–83% product yield [27]. The other reasons for considering the ILs consider as
green solvent or catalyst are ILs exhibit very appealing solvent properties and immiscibility with water or organic solvents due to the strong ionic (Coulomb-) interaction
or hydrogen bonding between the ions present in ILs. They have excellent capability
to being a good reaction medium for chemical synthesis reactions as compared to
organic solvents because ILs are found to be less toxic and high soluble with both
organic and inorganic materials [28]. Organic solvents are led to the high production
of considerable waste during drug synthesis and the synthesized drugs using organic
solvents are costly as well as not eco-friendly. Therefore, ILs are considered as good
alternate for reaction solvent in the synthesis of raw materials, intermediate and drug
substances as ILs are easily recovered and reused. To reduce the toxic and undesired
organic waste in pharmaceutical industries, the use of ILs in the manufacturing of
pharmaceutical was incorporated in 1990s due to excellent physical-chemical properties of ILs and thus ILs began to be considered as environmentally benign compared
to organic solvents. The solvation capability of ILs is decided by anions nature
because anions can form hydrogen bonds with the starting reaction material. The