Photoredox-Catalyzed Tandem Demethylation of N,N-Dimethyl Anilines Followed by Amidation with α-Keto or Alkynyl Carboxylic Acids

Article abstract of DOI:10.1002/adsc.201900525

We report herein, a biomimetic approach for highly selective monodemethylation of N,N-dimethyl anilines to generate secondary amines and subsequent coupling with α-ketocarboxylic acids or alkynyl carboxylic acids to form α-ketoamides or alkynamides respectively under visible light photoredox catalyst in a single operation. From the deuterium-labeling experiment, it was probed that demethylation is the slowest step in this tandem process. Whereas, control experiments and spectroscopic studies revealed that photoredox catalyst is also involved in the subsequent amidation step. The reaction proceeds smoothly at room temperature providing moderate to excellent yield of the coupling products. The amides have also been converted to a series of biologically active spiro compounds. (Figure presented.).

Full text of DOI:10.1002/adsc.201900525

Title: Photoredox-Catalyzed Tandem Demethylation of N,N-Dimethyl
Anilines Followed by Amidation with α-Keto or Alkynyl Carboxylic
Acids
Authors: Pritha Das, Hasina mamataj Begam, Samir Bhunia, and
Ranjan Jana
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To be cited as: Adv. Synth. Catal. 10.1002/adsc.201900525
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10.1002/adsc.201900525
Advanced Synthesis & Catalysis
FULL PAPER
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Photoredox-Catalyzed Tandem Demethylation of N,N-Dimethyl
Anilines Followed by Amidation with α-Keto or Alkynyl
Carboxylic Acids
Pritha Das,a Hasina Mamataj Begam,a Samir Kumar Bhunia,ab and Ranjan Jana*ab
a
Organic and Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road,
Jadavpur, Kolkata-700032, West Bengal, India
Phone: (+91) 33 2499 5819; fax: (+91) 33 2473 5197; e-mail: rjana@iicb.res.in
Academy of Scientific and Innovative Research (AcSIR), Kolkata-700032, India
b
Received: ((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.((Please
delete if not appropriate))
Abstract: We report herein, a biomimetic approach for highly selective monodemethylation of N,N-dimethyl
anilines to generate secondary amines and subsequent coupling with α-ketocarboxylic acids or alkynyl
carboxylic acids to form α-ketoamides or alkynamides respectively under visible light photoredox catalyst in
a single operation. From the deuterium-labeling experiment, it was probed that demethylation is the slowest
step in this tandem process. Whereas, control experiments and spectroscopic studies revealed that photoredox
catalyst is also involved in the subsequent amidation step. The reaction proceeds smoothly at room temperature
providing moderate to excellent yield of the coupling products. The amides have also been converted to a
series of biologically active spiro compounds.
Keywords: photoredox catalysis; demethylation; amidation; α-ketoamides; alkynamides.
development of environmentally benign tandem
reactions under visible-light catalysis.
Introduction
α-Ketoamides and alkynamides represent two
important classes of compounds ubiquitously found in
many natural products, pharmaceuticals, macrocycles,
molecular probes in chemical biology etc. (Figure 1).[5]
Furthermore, because of the integration of important
Tandem or domino reaction is comprised of two
or more bond cleavage/formation under the identical
reaction conditions and the reaction cascade is initiated
from the functionalities obtained in the former
transformation.[1] This domino reaction strategy has
unique ability to generate molecular complexity
reducing numbers of steps and environmental
footprints. This process is ubiquitously found in nature
for biosynthesis of natural products.[2] Inspired by
nature and owing to the green synthetic aspects, an
impressive array of cascade reactions involving
anionic, cationic or radical pathways has been well-
explored.[3] In the last decades, visible-light
photoredox catalysis has been proved as a powerful
strategy with a wide range of applications from small
molecule activation to the synthesis of complex natural
products mainly through single electron transfer (SET)
process.[4] Owing to close resemblance with the natural
processes, there is an increasing demand for the
Figure 1. Bioactive α-ketoamides and alkynamides.
1
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10.1002/adsc.201900525
Advanced Synthesis & Catalysis
functional groups such as ketone and amide for α-
ketoamides; and alkyne and amide for alkynamides
into their backbone they represent a versatile
intermediates in organic synthesis.[6] Hence, a
significant effort has been dedicated for the
construction of these structural motifs.[7] The synthesis
of α-ketoamides primarily involves amidation of α-
ketoacids and α-keto acyl halides;[8] oxidation of α-
hydroxyamides and α-aminoamides;[9] transition-
metal-catalysed double carbonylative amination of
aryl halides;[10] metal catalysed or metal free oxidative
coupling from α-ketoaldehyde etc.[11] The
alkynamides are derived through the amide coupling
of the propiolic acid derivatives, carbonylative
amidation of the corresponding alkyne etc.[12] Since
tertiary amines are readily obtained via over alkylation
of amines,[13] we assumed that in situ demethylation of
tertiary amines to secondary amines followed by
amide formation in a single operation under
photoredox catalysis could be an attractive approach.
In this vein, the Wang group reported a silver-
catalyzed dealkylative-amidation of α-ketoacids with
tertiary amines for the synthesis of α-ketoamides.[14]
However, only aliphatic tertiary amines were effective
using strong oxidant K2S2O8 at high temperature (120
catalysis. We report herein, a biomimetic approach for
the tandem demethylation of N,N-dimethylaniline
followed by amidation with α-ketoacids or alkynyl
carboxylic acids to furnish α-ketoamides or
alkynamides respectively by a single photoredox
catalyst. The present reaction initiates through the
generation of N-centred radical under the irradiation of
blue LED at room temperature.
Results and Discussion
N,N-dimethylaniline and phenyl glyoxalic acid
were chosen as model substrates to optimize the
reaction condition. The results are summarized in the
Table 1. When a mixture of N,N-dimethylaniline (1a)
and phenylglyoxilic acid (2a) was irradiated under
blue LED using 5 mol % of eosin Y as photocatalyst,
bromotrichloromethane as oxidant and 10:1 MeCN-
H2O solvent under air, the demethylative amidation
product was isolated in 20% yield (Table 1, entry 1).
Other oxidants such as TBHP, K2S2O8, BI-OAc, oxone
Table 1. Optimization of the reaction condition.[a,b]
oC).
Palladium/charcoal-catalyzed
oxidative
aminocarbonylation of alkynes with secondary and
tertiary amines through N-dealkylation was reported
for the synthesis of alk-2-ynamides whereas, alkylated
anilines were unreactive. [12] Thus, we were interested
to develop a complementary N-dealkylative amide
coupling reaction under mild conditions with the
challenging aniline derivatives. Recently, Rueping and
other groups reported Polonovski type N-
demethylation under photoredox catalysis.[15]
However, to the best of our knowledge there is no
report for the synthesis of α-ketoamides and acetylenic
amides from the corresponding α-ketoacids or
propiolic acids and tertiary amines under photoredox
Photocatalyst
Oxidant Additive
Entry
Yield
(%) 3a
20
1
2
Eosin Y
Eosin Y
BrCCl3
K2S2O8
TBHP
-
-
15
0
3
Eosin Y
-
4
Ru(bpy)3(PF6)2
Ru(bpy)3(PF6)2
BrCCl3
BrCCl3
-
32
45
80
0
5[c]
DABCO
6
Ru(bpy)3(PF6)2 BrCCl3 DABCO
7
Ru(bpy)3(PF6)2
Ru(bpy)3(PF6)2
Ru(bpy)3(PF6)2
Mes-Acr-ClO4
Ir(ppy)3
-
DABCO
DABCO
DABCO
DABCO
DABCO
DABCO
DABCO
8[d]
9[e]
10
11[f]
12
13[g]
BrCCl3
BrCCl3
BrCCl3
BrCCl3
BrCCl3
BrCCl3
44
65
52
66
0
-
Ru(bpy)3(PF6)2
0
[a]All reactions were carried out in 0.2 mmol scale using 1a
(1.0 equiv), 2a (2.0 equiv), Ru(bpy)3(PF6)2 (2.5 mol%),
BrCCl3 (1.5 equiv), DABCO (2.0 equiv) in 100:1
acetonitrile-water (0.06 M) solvent (3 mL) at room temp
with blue LED irradiation in aerobic condition. [b]Yields
refer to here are isolated yields. [c]20% additive was used.
[d]under nitrogen atmosphere. [e]O2-balloon. [f]white LED.
[g]without light.
Scheme 1. N-Demethylative-amide coupling.
2
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10.1002/adsc.201900525
Advanced Synthesis & Catalysis
did not improve the yield of the desired product
(entries 4-6, see Table S1 in the Supporting
Information, SI). The yield was increased to 32%
using 2.5 mol % Ru(bpy)3(PF6)2 as photocatalyst
(entry 4). Gratifyingly, upon addition of 20 mol %
DABCO as an additive, the product yield was
increased to 45% in 100:1 acetonitrile-water solvent
system (entry 5). To our delight, increasing the amount
of DABCO to 2.0 equiv, the desired product was
isolated in 80% yield in 36 h (entry 6). However, other
inorganic (entries 2-3, Table S1 in SI) and organic
bases (entries 15-17, Table S1 in SI) such as, K2CO3,
Cs2CO3, lutidine, DBU, pyridine were proved to be
inferior for this transformation. Organic photoredox
catalysts such as Rose Bengal, Mes-Acr-ClO4, 9-
fluorenone, were unable to increase the yield (entries
18-20, Table S1 in SI). In most of the cases, the starting
tertiary amine remained intact in the reaction medium.
Whereas, the iridium based photocatalysts such as
(Ir[dF(CF3)(ppy)]2(dtbpy))PF6, Ir(ppy)2(dtbpy)PF6,
Ir(ppy)3 provided better yield to some extent (entries
21-24, Table S1 in SI). However, a portion of N,N,-
dimethylaniline as well as the demetylated N-
methylaniline were isolated even after 36 hrs of
reaction. The yield of amide 3a was reduced to 58% at
methyl morpholine yielded demethylative amidation
in
39%
(3m).[17]
Furthermore,
2-oxo-2-
phenylacetaldehyde also provided 40% coupling
product in presence of O2-ballon (3a).
Next, we found that a range of phenyl glyoxylic acid
derivatives underwent this cascade reaction smoothly
under the optimized reaction condition (Scheme 3).
For example, methyl, isobutyl, tert-butyl, phenyl
substituted acids furnished the desired product in good
yields 72-78% (3n-3q). Halogens, such as (F, Br, I, 3r-
3t) were also survived under the reaction conditions
which is useful for further manipulations through
cross-coupling reactions. Electron donating
o
60 C (entry 33, Table S1 in SI). In this tandem
reaction, a photoredox catalyst, light source, BrCCl3
and DABCO were all necessary, since in the absence
of any one component the reaction was suppressed.
While an optimum yield (80%) was isolated under the
aerial conditions, whereas reaction under inert
atmosphere (44% yield) or oxygen atmosphere (65%)
provided inferior results (entries 8, 9). Since water is
crucial for the demethylation step, we have optimized
MeCN-water in 100:1 to obtain optimum yield of 3a.
To examine the substrate scope of this tandem
reaction, several substituted N,N-dimethylanilines
were reacted with 2-oxo-2-phenyl acetic acid, 2a
under the optimized reaction conditions (Scheme 2). A
variety of functional groups in the phenyl ring of
aniline were well-tolerated and furnished the desired
product in moderate to good yields. For example, 1a
with bulky tert-butyl and halogen (Br, I) substitution
at the para position yielded 67% (3b), 53% (3c) and
49% (3d) of the desired product respectively. p-OCF3
substituted N,N-dimethylaniline furnished 51% of the
desired product (3e). In presence of para-phenyl
substitution 72% yield was obtained (3f). Ortho-
substitution also did not hinder the reaction providing
the corresponding product in good yield for ortho
methyl (3h), ethyl (3i), isopropyl (3j) or aryl (3k)
substituted N,N-dimethylaniline. As expected,
demethylation/amidation cascade (3l) took place
predominantly over the corresponding deethylative
amidation (10%).[16] However, the demethylation step
generally does not occur with aliphatic tertiary amines.
Interestingly, in presence of 0.5 equiv TEMPO, N-
Reaction conditions: 1a (0.2 mmol), 2a (0.4 mmol),
Ru(bpy)3(PF6)2 (2.5 mol %), DABCO (0.4 mmol), BrCCl3
(0.3 mmol), MeCN/H2O=100:1 (0.06 M), blue LED, air, r.t
[a]2-oxo-2-phenylacetaldehyde was used instead of 2a, O2-
ballon. [b]Reaction time is15h. [c]N-ethyl-N-methyl aniline
was used. [d]N-methylmorpholine was used. 0.5 equiv
TEMPO was added.
Scheme 2. Substrate scope with tertiary aryl amines.
group such as para-methoxy (3v) has positive
influence providing 82% yield, whereas, electron
withdrawing group like -CF3 (3u) provided 57% yield.
Ortho methyl substituted ketoacid also delivered the
desired product in 82% yield (3w). Dichloro, dimethyl,
dimethoxy substituted acids were also compatible
providing high to excellent yields (3x-3z).
Additionally, 2-oxo-2-(thiophen-2-yl)acetic acid, 2-
(naphthalen-1-yl)-2-oxoacetic acid, 2-(naphthalen-2-
yl)-2-oxoacetic acid reacted efficiently with dimethyl
3
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10.1002/adsc.201900525
Advanced Synthesis & Catalysis
aniline furnishing the desired product in 47%, 94% and
76%
respectively
(3ab-3ad).
para-Methoxy
substituted acid reacted smoothly with para-fluoro and
para-methoxy substituted dimethylaniline delivering
the desired product in good yields (3ae, 3af).
This demethylation followed by amidation
reaction can also be extended to alkynyl carboxylic
acids (Scheme 4). The amine 1a is employed to react
with various alkynyl carboxylic acids to furnish the
desired products in moderate to good yields. Electron
donatng -OCF3 substituted alkynyl carboxylic acid
furnished the amidation product in 57% yield (3ai).
Reaction conditions: 1a (0.2 mmol), 2ab (0.6 mmol),
Ru(bpy)3(PF6)2 (2.5 mol %), DABCO (0.4 mmol), CBr4
(0.24 mmol), MeCN/H2O=100:1 (0.06 M), blue LED, air, r.t.
Scheme 4. Substrate scope with phenyl propiolic acid.
dimethylaniline (Scheme 5b). Further it was reacted
with 2a to afford the desired amide product (3f) in 68%
yield. Therefore, initially, photoredox mediated C-N
bond cleavage to generate secondary amine
intermediate takes place which undergoes subsequent
amidation reaction.
Reaction conditions: 1a (0.2 mmol), 2a (0.4 mmol),
Ru(bpy)3(PF6)2 (2.5 mol %), DABCO (0.4 mmol), BrCCl3
(0.3 mmol), MeCN/H2O=100:1 (0.06 M), blue LED, air, r.t.
[a] Reaction time 15hrs.
Scheme 3. Substrate scope with α-keto carboxylic
acids.
Electron-withdrawing -COMe substitution at the acid
moiety is well-tolerated delivering moderate yield of
the desired product (3aj). 3-(Naphthalen-1-
yl)propiolic acid also afforded the corresponding
product in 52% yield (3ak).
Next, we performed a series of control
experiments to understand the mechanism of this
tandem reaction. From an intermolecular experiment
with 1a and d6-1a the kH/kD was determined as 2.6,
which indicates that C-H bond cleavage may be
involved in the rate determining step (Scheme 5a). In
the absence of 2a, mono-demethylated product (I) was
isolated and characterized from 4-phenyl-N,N-
Scheme 5. Control experiments.
When the secondary amine intermediate is allowed to
react with 2a in absence of light or photocatalyst, no
desired product was obtained (Scheme 5c). Hence,
photoredox catalytic cycle is involved in the amidation
step also.[11] Typically, an activated precursor such as
4
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10.1002/adsc.201900525
Advanced Synthesis & Catalysis
acid bromide or hypobromite may generate through
radical pathway from the carboxylic acids for
subsequent amide coupling.[15d] Although, all our
efforts to identify this activated precursor were in vain,
the corresponding carboxyl radical was trapped by 1,1-
diphenylethylene to provide II in 18% isolated yield
(Scheme 5d). However, we have observed positive
intermediate 2 by releasing one hydrogen radical,
which in the presence of water undergoes
influence
of
2,2,6,6-tetramethylpiperidinyloxy
(TEMPO) or butylated hydroxytoluene (BHT) in the
reaction outcome presumably due to facilitation in the
demethylation step.[17]
In Stern-Volmer quenching experiments of the
photocatalyst, it was observed that the emission
intensity of excited state of the photocatalyst
Ru(bpy)3(PF6)2* was gradually diminished with
increasing concentration of both 1a and 2a (Figure 2).
But such a phenomenon was not observed with BrCCl3
or DABCO. These results suggest that an amine
radical cation as well as a carboxyl radical is most
likely involved in the reaction.
Although the proper mechanistic understanding
for the amidation is not clear at this stage and need
more detailed study. From these control experiments
and previous literatures, a plausible mechanism is
depicted in Scheme 6 for this tandem C-N activation/
C-N formation process.[18] Ru(II)-photocatalyst is
Scheme 6. Plausible reaction mechanism.
demethylation of N,N-dimethylaniline by elimination
of formaldehyde and secondary amine 4 via the
inherently unstable carbinolamine intermediate 3.[19]
In an another catalytic cycle, the excited Ru(II)* can
oxidize the carboxylate anion, which is generated from
2a to carboxylate radical 5. In presence of BrCCl3 the
carboxylate radical may form the reactive bromide or
hypobromite intermediate 6 which upon reacting with
4 furnishes the desired product 3a.
Next we turned our attention for further utilization
of α-ketoamide products to the synthesis of useful
Figure 2. Stern-Volmer plot of Ru(bpy)3(PF6)2 in
presence of different components of the reaction. I0 is
the inherent fluorescence intensity of photocatalyst. I
is the fluorescence intensity of photocatalyst in the
presence of quenchers.
first excited upon irradiation of the blue LED to
red
generate the excited state photocatalyst Ru(II)* (E1/2
=
0.77
V
vs
SCE)
which
undergoes
thermodynamically feasible one electron reduction
with N,N-dimethylaniline (E1/2 red = 0.74 V vs SCE) to
form the α-amino radical cation 1.[4e] The reduced
photocatalyst then returns to its original ground state
for the next run by a single electron oxidation with
molecular O2 or BrCCl3. The generated α-amino
radical cation can readily form the iminium cation
Scheme 7. Application of demethylative-amide
coupling for molecular complexity.
5
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10.1002/adsc.201900525
Advanced Synthesis & Catalysis
on Fourier transform infrared spectroscopy; only intense
peaks were reported. Fluorescence spectra were recorded on
a Perkin Elmer LS 55 Luminescence Spectrometer. Unless
otherwise stated, all commercial reagents were used without
additional purification. The starting materials α-
molecules. When an ethylaryl substituted aniline 1b
was subjected to the standard reaction condition with
2a, an orexin receptor antagonist 3al was isolated in
moderate yield (Scheme 7a).[20] α-Ketoamide, 3a is
transformed into α-hydroxyamide by chemoselective
reduction of the ketone group with NaBH4. After
oxocarboxylic acid;[24] alkynyl carboxylic acid;[25] and
[26]
metal-photocatalysts
reported method.
were prepared using literature
2
mesylation of the hydroxyl group followed by SN
substitution with sodium azide the corresponding
azido-amide compound was obtained. It was
converted to azaspirocyclohexadieneone 3am using
catalytic Cu(OAc)2 under oxygen atmosphere
(Scheme 7b).[21] Furthermore, 3a rearranges to provide
3,3-disubstituted oxyindole 3an in superacidic
condition (Scheme 7c).[22] The alkynamide product
3ag undergoes selenylative spirocyclization with
diphenyldiselenide to form 3ao in presence of blue
LED under oxygen atmosphere (Scheme 7d).[23]
General experimental procedure for photoredox
catalyzed α-ketoamide synthesis from the corresponding
N,N-dimethylaniline and 2-oxo-2-phenylacetic acid.
(Scheme 4):
A mixture of N,N-dimethyl aniline (0.2 mmol, 1.0 equiv),
Ru(bpy)3(PF6)2 (4.3 mg, 0.005 mmol, 0.025 equiv),
DABCO (44.8 mg, 0.4 mmol, 2.0 equiv) and 2-oxo-2-
phenylacetic acid (60 mg, 0.4 mmol, 2.0 equiv) was taken
in a 25 mL round bottom flask and diluted with 3 mL of
acetonitrile solvent. To this mixture, were added
bromotrichloromethane (30 μL, 0.3 mmol, 1.5 equiv) and
water (30 μL). The resulting mixture was irradiated under
blue LED (48 W) light and stirred at room temperature for
36 h in aerobic condition. After that the acetonitrile solvent
was evaporated in reduced pressure and the reaction mixture
was poured into ethyl acetate (30.0 mL) and extracted with
saturated aqueous NaHCO3 solution. The organic layer was
washed with water (10 mL x 2) and brine (10 mL), dried
over anhydrous Na2SO4 and the solvent was evaporated
under reduced pressure. The crude product was purified by
column chromatography (SiO2, eluting with hexane/ethyl
acetate) to afford the desired product.
Conclusion
In conclusion, we have developed a biomimetic
catalytic approach for demethylative-amide bond
formation between N,N-dimethylaniline and α-
ketocarboxylic acid or alkynyl carboxylic acid. These
two distinct steps proceed smoothly in a cascade
manner under
a
single visible-light-mediated
phororedox catalysis at room temperature. A series of
extremely important class of compounds, α-
ketoamides and alkynamides have been synthesized
through this protocol which ubiquitously found in
natural products, peptoids and useful synthetic
intermediates. The demethylative-amide coupling
products were easily converted to a series of
biologically active complex spiro compounds. We
anticipate that integration of two or more important
reactions in a cascade manner under photoredox
catalysis will open a new arena in organic synthesis.
General experimental procedure for photoredox
catalyzed alkynamide synthesis from the corresponding
N,N-dimethylaniline and phenyl propiolic acid. A
mixture of N,N-dimethyl aniline (0.2 mmol, 1.0 equiv),
Ru(bpy)3(PF6)2 (4.3 mg, 0.005 mmol, 0.025 equiv),
DABCO (44.8 mg, 0.4 mmol, 2.0 equiv) and phenyl
propiolic acid (44 mg, 0.6 mmol, 3.0 equiv) was taken in a
25 mL round bottom flask and diluted with 3 mL of
acetonitrile solvent. To this mixture were added
tetrabromomethane (80 mg, 0.24 mmol, 1.2 equiv) and
water (30 μL). The resulting mixture was irradiated under
blue LED (48 W) light and stirred at room temperature for
20 h in aerobic condition. After that the acetonitrile solvent
was evaporated in reduced pressure and the reaction mixture
was poured into ethyl acetate (30.0 mL) and extracted with
saturated aqueous NaHCO3 solution. The organic layer was
washed with water (10 mL x 2) and brine (10 mL), dried
over anhydrous Na2SO4 and the solvent was evaporated
under reduced pressure. The crude product was purified by
column chromatography (SiO2, eluting with hexane/ethyl
acetate) to afford the desired product.
Experimental Section
General Information.
Melting points were determined in open end-capillary tubes
and are uncorrected. TLC was performed on silica gel plates
(Merck silica gel 60, f254), and the spots were visualized with
UV light (254 and 365 nm) and KMnO4 stain. 1H NMR was
recorded at 300 MHz (Bruker-DPX), 400 MHz (JEOL-
JNM-ECZ400S/L1) and 600 MHz (Bruker-Avance)
frequency and 13C NMR spectra were recorded at 75 MHz
(Bruker-DPX) and 150 MHz (Bruker-Avance) frequency in
CDCl3 solvent using TMS as the internal standard.
Chemical shifts were measured in parts per million (ppm)
referenced to 0.0 ppm for tetramethylsilane. The following
abbreviations were used to explain multiplicities: s = singlet,
d = doublet, t = triplet, q = quartet, m = multiplet, br. = broad,
Ar = aromatic. Coupling constants, J were reported in Hertz
Acknowledgements
This work was supported by DST, SERB, Govt. of India, extra
mural research grant no. EMR/2014/000469 and Ramanujan
fellowship; award no. SR/S2/RJN-97/2012. PD and HM thank
CSIR and SKB thanks UGC for their fellowships.
unit (Hz). HRMS (m/z) were measured using ESI (Q-TOF, References
positive ion) techniques. Infrared (IR) spectra were recorded
6
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10.1002/adsc.201900525
Advanced Synthesis & Catalysis
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10.1002/adsc.201900525
Advanced Synthesis & Catalysis
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10.1002/adsc.201900525
Advanced Synthesis & Catalysis
FULL PAPER
Photoredox-Catalyzed Tandem Demethylation of
N,N-Dimethyl Anilines Followed by Amidation
with α-Keto or Alkynyl Carboxylic Acids
Adv. Synth. Catal. Year, Volume, Page – Page
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Bhunia and Ranjan Jana*
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