Abstract:Hemicyanine derivatives C1–C4 have been synthesized and utilized as photocatalysts in additive/base free oxidative amidation of aromatic aldehydes in mixed aqueous media under visible light irradiation at low catalytic loading.
“…The in-situ generated H 2 O 2 acts as an oxidant and is responsible for the oxidative amidation of aromatic aldehyde under the natural sunlight irradiation to give the desired product (D) through the formation of (C) (Fig. 14) 44 .Figure 14Proposed mechanism for oxidative amidation of aromatic aldehydes using supramolecular assemblies of TETPY under natural sunlight and aerial conditions.…”
Section: Photocatalytic Activity Of the Supramolecular Assemblies Of mentioning
Pyrazine derivatives
DIPY
,
TETPY
and
CNDIPY
have been designed and synthesized which form fluorescent supramolecular assemblies in mixed aqueous media due to their AIEE and ICT characteristics. Among all the derivatives, the assemblies of
TETPY
and
CNDIPY
show strong absorption in the visible region with high absorption coefficients, low HOMO-LUMO gap, and high photostability. Further, the supramolecular nanoassemblies of
TETPY
and
CNDIPY
show excellent potential to generate reactive oxygen species (ROS) under the visible light irradiation. Owing to their strong absorption in the visible region and ROS generation ability, the supramolecular nanoassemblies of
TETPY
and
CNDIPY
act as efficient photoredox catalytic systems for carrying out (a) oxidative amidation of aromatic aldehydes (b) hydroxylation of boronic acid and (c) oxidative homocoupling of benzylamines under mild conditions such as aqueous media, aerial environment, and natural sunlight as a source of irradiation. All the mechanistic investigations suggest the participation of
in-situ
generated ROS in the organic transformations upon light irradiation.
“…The in-situ generated H 2 O 2 acts as an oxidant and is responsible for the oxidative amidation of aromatic aldehyde under the natural sunlight irradiation to give the desired product (D) through the formation of (C) (Fig. 14) 44 .Figure 14Proposed mechanism for oxidative amidation of aromatic aldehydes using supramolecular assemblies of TETPY under natural sunlight and aerial conditions.…”
Section: Photocatalytic Activity Of the Supramolecular Assemblies Of mentioning
Pyrazine derivatives
DIPY
,
TETPY
and
CNDIPY
have been designed and synthesized which form fluorescent supramolecular assemblies in mixed aqueous media due to their AIEE and ICT characteristics. Among all the derivatives, the assemblies of
TETPY
and
CNDIPY
show strong absorption in the visible region with high absorption coefficients, low HOMO-LUMO gap, and high photostability. Further, the supramolecular nanoassemblies of
TETPY
and
CNDIPY
show excellent potential to generate reactive oxygen species (ROS) under the visible light irradiation. Owing to their strong absorption in the visible region and ROS generation ability, the supramolecular nanoassemblies of
TETPY
and
CNDIPY
act as efficient photoredox catalytic systems for carrying out (a) oxidative amidation of aromatic aldehydes (b) hydroxylation of boronic acid and (c) oxidative homocoupling of benzylamines under mild conditions such as aqueous media, aerial environment, and natural sunlight as a source of irradiation. All the mechanistic investigations suggest the participation of
in-situ
generated ROS in the organic transformations upon light irradiation.
“…Both DDQ and 1,4benzoquinone have been tested previously for the same purposes in comparison with other oxidizing without good results. 12a, 17,18 The quantity of oxidizing agent used in this work is very low. In a typical reaction, 0.02 mmol was reacted with 0.66 mmol aldehyde.…”
Section: Resultsmentioning
confidence: 99%
“…4 Recently, several groups reported photocatalytic methods based on phenazinium, 13 Rose Bengal, 14 BODIPY, 15 quinolizinium compounds, 16 and hemicyanine derivatives. 17 This paper describes the use of pyrrolyl quinones (Scheme 1) as efficient oxidant in the oxidative amidation of benzaldehyde.…”
An efficient transition-metal-based heterogeneous catalyst free procedure for obtaining the oxidative amidation of benzaldehyde using quinones as oxidizing agents in low molar proportions is described here.
“…The influence of substituents on benzaldehyde is consistent with that reported in the literature. [32][33][34][35][36][37][38] Both chloro and bromo substituents werew ell tolerated under the developed reactionc onditions, providing ane asy meansf or further synthetic elaboration. In particular,i sophthalaldehydea nd terephthalaldehyde, with two aldehyde groups, reactedw ith one equivalent of pyrrolidinet oa fford the monoamidation products 3r and 3s in 81 and 83 %y ield, respectively.I ti sw orth noting that this protocol was also efficient for polycyclic and heterocyclic aromatic aldehydes, and the corresponding amides 3t-3w were obtained in moderate to good yields.…”
Section: Amidation Of Aromatic Aldehydesmentioning
confidence: 97%
“…However, some of these strategies have inherent shortcomings, such as the employment of expensive transition-metal catalysts, elevated temperature, or superfluous use of strong oxidants. In recentp hotochemicals tudies, visible-light photoredox catalysis has provided optional approaches for the oxidative amidation of aldehydes by using ap henazinium salt, [32] rose Bengal, [33] boron-dipyrromethene (BODIPY), [34] silyl-substituted quinolizinium compounds, [35] hemicyanine derivatives (CAT), [36] Ag/graphitic carbon nitride (g-C 3 N 4 ), [37] or anthraquinone (AQN)-based organophotocatalysts [38] (Scheme 1d). Nonetheless,m ost existing methodsi nvolve the use of expensive catalysts and requirea dditives, and the separation of homogeneous photocatalystsi s still problematic.…”
Am agnetic CdS quantum dot(Fe 3 O 4 /polydopamine (PDA)/CdS) was synthesized through af acile and convenient method from inexpensives tarting materials. Characterization of the prepared catalyst was performedb ym eans of FTIR spectroscopy,X RD, SEM, TEM, energy-dispersive Xray spectroscopy, and vibrating-samplem agnetometert ech-niques. Fe 3 O 4 /PDA/CdS was found to be ah ighly active photocatalyst for the amidation of aromatic aldehydes by using air as ac lean oxidantu nder mild conditions. The photocatalyst can be recovered by magnetic separation and successfully reused for five cycles without considerable loss of its catalytic activity.
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