sp2-C–H Acetoxylation of Diversely Substituted (E)-1-(Arylmethylene)-2-phenylhydrazines Using PhI(OAc)2 as Acetoxy Source at Ambient Conditions

Article abstract of DOI:10.1002/ejoc.201900994

A catalyst- and additive-free simple and straightforward method for regioselective direct sp2 C–H acetoxylation reaction of aldehyde hydrazones has been achieved at ambient temperature employing PIDA as an acetoxy source. The scope of the reaction has been successfully verified with a wide range of biologically important aldehyde hydrazones with diverse functional group tolerance. The method is highly selective, mild and efficient, operationally simple, rapid and high-yielding.

Full text of DOI:10.1002/ejoc.201900994

A Journal of
Accepted Article
Title: Catalyst- and additive-free sp2 C-H acetoxylation of diversely
substituted (E)-1-(arylmethylene)-2-phenylhydrazines using
PhI(OAc)2 as acetoxy source at ambient conditions
Authors: Goutam Brahmachari and Indrajit Karmakar
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201900994
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10.1002/ejoc.201900994
European Journal of Organic Chemistry
Full Paper
Catalyst- and additive-free sp2 C-H acetoxylation of diversely substituted (E)-1-
(arylmethylene)-2-phenylhydrazines using PhI(OAc)2 as acetoxy source at ambient
conditions
Prof. Dr. Goutam Brahmachari* and Indrajit Karmakar
aLaboratory of Natural Products & Organic Synthesis, Department of Chemistry,
Visva-Bharati(a Central University), Santiniketan-731 235, West Bengal, India
E-mail:brahmg2001@yahoo.co.in; goutam.brahmachari@visva-bharati.ac.in
*Corresponding author: Prof. Dr. Goutam Brahmachari
(http://orcid.org/0000-0001-9925-6281)
Home page: http://vbchem.ac.in/GoutamBrahamachari/
GRAPHICAL ABSTRACT
C−H Acetoxylation
________________________________________________________________________
It’s Simple! Catalyst- and additive-free regioselective direct sp2 C−H acetoxylation reaction of biologically
interesting aldehyde hydrazones to access a new series of hydrazone acetates has been achieved just at ambient
temperature employing PIDA as an acetoxy source.
___________________________________________________________________________
1
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10.1002/ejoc.201900994
European Journal of Organic Chemistry
_________________________________________________________________________________
ABSTRACT: A catalyst- and additive-free simple and straightforward method for regioselective
direct sp2 C−H acetoxylation reaction of aldehyde hydrazones has been achieved at ambient
temperature employing PIDA as an acetoxy source. The scope of the reaction has been successfully
verified with a wide range of biologically important aldehyde hydrazones with diverse functional
group tolerance. The method is highly selective, mild and efficient, operationally simple, rapid and
high-yielding.
KEYWORDS: sp2 C−H bond functionalization; aldehyde hydrazones; PIDA; metal-free
acetoxylation; catalyst- and additive-free synthesis
__________________________________________________________________________________
INTRODUCTION
During the recent past the process of C−H bond functionalization with useful functional groups in
diverse molecular systems under various reaction conditions, particularly aided by transitional metal
catalysis, has emerged as one of the most highly useful tools in modern organic synthesis.[1] The
inherent beauty of this type of reaction is to enable regioselective cleavage and substitution of
ubiquitously existing C−H bonds in starting organic substrates at the proximate position to the
directing group. Literature survey reveals a variety of such reactions involving the sequence of
regioselective C−H bond cleavage/C−C bond formation, but the processes via C−H bond
cleavage/C−heteroatom bond formation have been relatively less explored.[2] Very recently, the direct
formation of a C−O bond has received much attention among the synthetic organic chemists.[3] As part
of these endeavors, introduction of an acetoxy group via C−H functionalization has currently
appeared to be much fascinating so as to impart certain key drug-like properties into desired
molecules. The acetoxy group acts as a functional group modifier, and imparts the unique H-bond
donor accepting capacity, thereby inducing effective polar nature in the product that eventually
enhances its pharmaceutical importance as a whole. This phenomenon is reflected in a plethora of
potentially useful pharmaceuticals and agrochemicals, wherein the acetoxy group forms a key
structural part.[4] Newer methods of regiospecifically introducing this group in biologically promising
organic molecules continues therefore to be of particular relevance.
As results, a good deal of research on direct sp2 and sp3 C−H bond acetoxylations for varying
organic scaffolds has been accomplished mostly based on palladium catalysis,[5] and less commonly
with rhodium,[6] ruthenium[7] and copper[8] catalysts. In addition, a couple of metal-free sp2 C−H bond
acetoxylations have also been reported in recent times.[9] However, all these methods are associated
with several drawbacks such as the excessive use of metallic acetoxy sources and/or toxic silver
oxidants, strong acids and/or acetic anhydride as additive, toxic organic solvents and high
temperature, which limit their application toward substrates bearing various sensitive functional
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10.1002/ejoc.201900994
European Journal of Organic Chemistry
groups and complex moieties. Recently, PhI(OCOCH3)2 (PIDA) has been found to be an efficient
source for acetoxy group in implementing sp2 C−H bond acetoxylations[6a,10] as documented in
Scheme 1, and all these methods also involve metal catalysts, additives and high temperature. As part
of our ongoing endeavors in green chemistry research,[11] we were thus motivated to develop a green
and milder approach to regioselective and direct sp2 C−H bond acetoxylation of certain biologically
relevant organic scaffolds. For this purpose, we screened aldehyde hydrazones as our substrates.
Hydrazones represent as an important class of structural motifs that frequently occur in numerous
biologically potent and pharmaceutically useful molecules[12] and in fluorescent chemosensors,[13] and
find applications as auxiliaries in asymmetric synthesis,[14] photo switches in photopharmacology,[15]
and linkers in preparing bifunctional molecules[16] and as ligands or directing groups in organic
synthesis.[17] To our delight, we have now been successful in developing a catalyst- and additive-free
efficient and practical method for regioslective direct sp2 C−H bond acetoxylation of diversely
substituted (E)-1-(arylmethylene)-2-phenylhydrazines (1) upon reaction with PhI(OCOCH3)2
(PIDA)/PhI(OCOCF3)2 (PIFA) (2) in 1,4-dioxane at ambient conditions to access a new series of
functionalized (Z)-1-(1-acetoxy-1-arylmethylene)-2-phenylhydrazines (3) (Scheme 1). The key
advantages of this protocol are use of commercially available low-cost starting materials, catalyst- and
additive-free acetoxylation, metal-free synthesis, mild reaction conditions at ambient temperature,
energy efficiency, short reaction times, large-scale synthetic application, and good to excellent yields.
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European Journal of Organic Chemistry
Scheme 1. Overview of previously reported and present strategy for regioselective direct sp2 C−H
mono-acetoxylation of diverse organic scaffolds employing PIDA as acetoxy source
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RESULTS AND DISCUSSION
We commenced our studies with (E)-1-(4-nitrophenylmethylene)-2-phenylhydrazine (1-1) as the
model substrate for acetylation via functionalization of its sp2 C-H hydrogen, and accordingly, we
performed a series of trial reactions using varying acetate sources (viz. PIDA, MnIII(OAc)2,
CuII(OAc)2, and NH4OAc) and solvents (viz. H2O, EtOH, CH3CN, CH2Cl2, and 1,4-dioxane) at
ambient conditions in the absence of any catalysts/additives (Table 1, entries 1-10). Among the
acetylating agents tried with, only PIDA was found to carry out the transformation in organic solvents
(no reaction occurred in water medium), indicating 1,4-dioxane as the best suited solvent in terms of
reaction time and product-yield. We were delighted to isolate the desired product (Z)-1-(1-acetoxy-1-
(4-nitrophenyl)methylene)-2-phenylhydrazine (3-1) in 95% yield within 15 min upon reaction with
1.0 equiv. of PhI(OAc)2 (phenyliodine(III) diacetate; PIDA) in 1,4-dioxane at room temperature
(Table 1, entry 8). It was also thus revealed the crucial role of 1,4-dioxane as solvent in implementing
13
the conversion. Compound 3-1 was characterized by its analytical and spectral (1H NMR, C NMR,
DEPT-135 and HRMS) studies. The overall results are summarized in Table 1.
Table 1
Optimization of Reaction Conditions for the Synthesis of diversely functionalized (Z)-1-(aryl-1-
acetoxymethylene)-2-phenylhydrazines (3)
entry acetate reagent (equiv)
solvent
conditions time
(min)
yield (%)a,b
1
2
PIDAc(1.0)
CH3CN (1.5 mL)
CH3CN (1.5 mL)
EtOH (1.5 mL)
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
90
86
41
81
−
−
−
PIDA (0.5)
360
90
3
PIDA (1.1)
4
PIDA (1.0)
H2O (1.5 mL)
360
360
360
360
15
5
MnIII(OAc)2 (1.0)
CuII(OAc)2 (1.0)
NH4OAc (1.0)
PIDA (1.0)
CH3CN (1.5 mL)
CH3CN (1.5 mL)
CH3CN (1.5 mL)
1,4-Dioxane (1.5 mL)
1,4-Dioxane (2.0 mL)
CH2Cl2 (1.5 mL)
6
7
−
8
95
96
88
9
PIDA (1.0)
15
10
PIDA (1.0)
30
aReaction conditions: (E)-1-(4-nitrophenylmethylene)-2-phenylhydrazine (1-1; 0.25 mmol) was
reacted with varying amounts of different acetate reagents (2-1) in aqueous/non-aqueous
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10.1002/ejoc.201900994
European Journal of Organic Chemistry

b
solvent(s) in the absence of any catalyst/additive at room temperature (rt; 28-30 C). Isolated
yields. cPIDA: phenyliodine(III) diacetate [PhI(OAc)2]
With the optimized reaction conditions in hand, we then proceeded to check the generality as well
as the effectiveness of this newly developed protocol by carrying out the sp2 C-H functionalization
with acetoxyl group for a set of six substrates such as (E)-1-(phenylmethylene)-2-phenylhydrazine
(1-2)/
cyanophenylmethylene)-2-phenylhydrazine
trifluoromethylphenylmethylene)-2-phenylhydrazine
(E)-1-(3-nitrophenylmethylene)-2-phenylhydrazine
(1-3;
0.25
mmol)/
0.25 mmol)/
mmol)/
(E)-1-(4-
(E)-1-(4-
(E)-1-(2-
(1-4;
0.25
(1-5;
fluorophenylmethylene)-2-phenylhydrazine (1-6; 0.25 mmol)/ (E)-1-(4-fluorophenylmethylene)-2-
phenylhydrazine (1-7; 0.25 mmol) using PIDA (2; 0.25 mmol) in 1.5 mL of 1,4-dioxane at room
temperature; all the reactions took place efficiently furnishing the expected productsviz. (Z)-1-(1-
acetoxy-1-phenylmethylene)-2-phenylhydrazine (3-2)/ (Z)-1-(1-acetoxy-1-(3-nitrophenyl)methylene)-
2-phenylhydrazine (3-3)/ (Z)-1-(1-acetoxy-1-(4-cyanophenyl)methylene)-2-phenylhydrazine (3-4)/
(Z)-1-(1-acetoxy-1-(4-trifluoromethylphenyl)methylene)-2-phenylhydrazine (3-5)/ (Z)-1-(1-acetoxy-
1-(2-fluorophenyl)methylene)-2-phenylhydrazine
(3-6)/
(Z)-1-(1-acetoxy-1-(4-
fluorophenyl)methylene)-2-phenylhydrazine (3-7), in 88%, 94%, 92%, 94%, 90% and 87% yield,
respectively, within 8-20 min. With these satisfactory results, we then prepared a set of five more
hydrazone derivatives (1-8 – 1-12) of aldehydes bearing electron-donating substituents such as
hydroxyl, methyl, mono- and di-methoxyl, and methylenedioxyl. All these aldehyde hydrazones 1-8 –
1-12 underwent the reaction affording the desired acetoxylated products 3-8 – 3-12 (Table 2),
respectively in 76%, 93%, 93%, 93% and 91% yield at 40, 10, 15, 25 and 22 min. It appeared that the
hydroxyl group among the series exerts the highest retarding effect both in terms of reaction time (80
min) and product-yield (76%) as expected. The hydrazone derivatives of isophthalaldehyde (1-13) and
terephthalaldehyde (1-14) also took somewhat longer reaction time (80 and 50 min, respectively) but
produced the desired products 3-13 and 3-14 with respective excellent yields of 91% and 94% (Table
2), keeping the second carboxyladehyde (CHO) function intact. We could not check the effect of
hydrazone of phthalaldehyde in this reaction because we were unable to prepare the hydrazone as per
our protocol, possibly due to the high-degree of steric constraint in the substrate. However, the
hydrazone of cinnamaldehyde (1-15) underwent the acetoxylation reaction efficiently under the
optimized reaction conditions giving rise to (Z)-1-(1-acetoxy-1-styrylmethylene)-2-phenylhydrazine
(3-15) in 87% yield at 30 min (Table 2).
Encouraged by these results, we then replaced PhI(OCOCH3)2 (PIDA) with PhI(OCOCF3)2
(PIFA) and performed two more reactions with (E)-1-(phenylmethylene)-2-phenylhydrazine (1-2)
and (E)-1-(4-nitrophenylmethylene)-2-phenylhydrazine (1-1) using identical reaction conditions when
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we successfully isolated the targeted products, (Z)-1-(1-trifluoroacetoxy-1-phenylmethylene)-2-
phenylhydrazine (3-16) and (Z)-1-(1-trifluoroacetoxy-1-(4-nitrophenyl)methylene)-2-phenylhydrazine
(3-17) with respective yields of 91% and 92%, at 10 and 5 min (Table 2). With these inspiring
experimental outcomes, we were then motivated to explore the substrate scope of the present reaction
with varying aldehyde hydrazones. Accordingly, we prepared a series of hydrazone derivatives (1-16
– 1-24) from the reaction between diversely substituted (both with electron-donating and electron-
withdrawing functionalities) aromatic aldehydes and phenyl hydrazines, followed by their respective
sp2 C-H acetoxylation with PIDA using the same reaction conditions. All these hydrazones took part
in the reaction smoothly to generate respective acetoxylated products 3-18 – 3-26 (Table 2) with good
yields ranging from 71-97% within reasonable time-frame of 5-120 min. To our delight, two more
hydrazones, (E)-1-(naphthalen-1-ylmethylene)-2-phenylhydrazine (1-25) and (E)-1-phenyl-2-
(thiophen-2-ylmethylene)hydrazine (1-26), also underwent this reaction effectively to afford the
desired acetoxylated products, (Z)-1-(1-acetoxy-1-(2-naphthyl)methylene)-2-phenylhydrazine (3-27)
and(Z)-1-(1-acetoxy-1-(2-thienyl)methylene)-2-phenylhydrazine (3-28) with respective yields of 99%
and 97%, at 30 and 15 min. The overall results are documented in Table 2. The synthesized
products (3-1–3-28) were purified using column chromatography (see experimental). All are new
compounds and were fully characterized on the basis of their analytical data and detailed spectral
studies including 1H NMR, 13C NMR, DEPT-135 and HRMS (in case of representative entries).
Table 2
Synthesis of diversely functionalized diversely functionalized (Z)-1-(aryl-1-acetoxymethylene)-2-
phenylhydrazines (3)a,b
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__________________________________________________________________________________
aReaction conditions: (E)-1-(arylmethylene)-2-phenylhydrazines (1; 0.25 mmol) and PhI(OCOCH3)2
(PIDA)/ PhI(OCOCF3)2 (PIFA) (2; 0.25 mmol) in 1.5 mL of 1,4-dioxane at ambient conditions.
bIsolated yields.
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European Journal of Organic Chemistry
We herein propose a possible mechanism for this sp2 C-H functionalization of aldehyde
hydrazones with acetoxy group, as depicted in Scheme 2, upon reaction with PhI(OCOCH3)2 in 1,4-
dioxane under the optimized condition. Initially, N-H proton of 1 is abstracted by one of the acetoxyl
(-OCOCH3) groups within PIDA (2), followed by nucleophilic attack by the imino-carbon of 1 at the
electron-deficient iodine centre of 2 to form an intermediate 4 (non-isolable) with the removal of one
molecule of acetic acid. Intermediate 4 readily tautomerizes into 5, which then undergoes homolytic
cleavage for both its I−O and C−I bonds to generate an acetoxyl radical 6a[18] and an imino-radical
6b[19] with the elimination of PhI. In the final step, these in situ generated radicals 6a and 6b take part
in a radical recombination process to yield the desired product 3. In support of our proposition for this
radical pathway, we conducted sets of control experiments with our model reaction in the presence of
radical-trapping reagents (TEMPO and p-benzoquinone) (Table 3). It was observed that the formation
of product 3-1 was completely prohibited in case of using at least two equivalents of TEMPO or one
equivalent of p-benzoquinone, thereby suggesting the involvement of a radical process in the
transformation.[20]
Scheme 2: Proposed mechanism for the synthesis of sp2 C-H acetoxylation of substituted (E)-1-
(arylmethylene)-2-phenylhydrazines (1) by PIDA (2) in 1,4-dioxane at ambient conditions
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European Journal of Organic Chemistry
Table 3
Results of control experimentsa,b
Radical-Trapping reagent
Amount [mmol (equiv.)] Time (min)
3-1 (% yield)
0.0 (0.0)
15
30
30
30
30
15
30
30
30
30
95
42
trace
0
0.125 (0.5)
0.25 (1.0)
0.50 (2.0)
0.75 (3.0)
0.0 (0.0)
0
95
23
trace
0
0.062 (0.25)
0.125 (0.5)
0.25 (1.0)
0.50 (2.0)
0
aReaction conditions: (E)-1-(4-nitrophenylmethylene)-2-phenylhydrazine (1-1; 0.25 mmol)
and PIDA (2; 0.25 mmol) in the presence of varying amounts of TEMPO and p-benzoquinone

as the radical-trapping reagents in 1.5 mL of 1,4-dioxane at room temperature (rt; 28-30 C).
bIsolated yields.
We also verified the feasibility of the present method for a scaled-up (on the gram scale; 5 mmol
scale) experiment with the model reaction (Table 2, entry 1). The reaction completed within the same
time-scale of 15 min, affording the desired product 3-1 with a slight reduced isolated yield of 92%
(1.382 g; 5 mmol scale) compared to the results of 0.25 mmol scale entry (95% yield at 15 min). This
satisfactory experimental outcome thus confers the present protocol with a possibility of large-scale
synthetic applications.
CONCLUSION
In conclusion, we have developed a simple, highly efficient, and room temperature-based
conveniently practical method for easy access to a new series of functionalized (Z)-1-(1-acetoxy-1-
arylmethylene)-2-phenylhydrazines (3) in good to excellent yields via regioselective direct sp2 C−H
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acetoxylation of diversely substituted (E)-1-(arylmethylene)-2-phenylhydrazines (1) upon reaction
with PhI(OCOCH3)2 (PIDA)/ PhI(OCOCF3)2 (PIFA) (2) in 1,4-dioxane at ambient conditions without
the aid of any catalysts and/or additives. The salient features of this present protocol include mild
reaction conditions at ambient temperature, avoidance of catalyst and additive, metal-free
acetoxylation, energy-efficiency, operational simplicity, short reaction times, large-scale synthetic
application, and good to excellent yields.
EXPERIMENTAL SECTION
General. All chemicals (analytical grade) except starting hydrazine substrates were purchased from
reputed companies and used without further purification. All the starting aldehyde hydrazones (1-1-1-
26) used in this present study were synthesized in our laboratory (based on a water-mediated and
ultrasound-promoted catalyst-free protocol as newly developed by us for this purpose; details of the
process along with the compound characterizations data are supplemented in the Supporting
1
13
Information). H and C NMR spectra were collected at 400 MHz and 100 MHz, respectively, on a
Bruker DRX spectrometer using DMSO-d6 and CDCl3 as solvent. Chemical shifts were reported in δ
(ppm), relative to the internal standard, TMS. The signals observed are described as s (singlet), d
(doublet), t (triplet), and m (multiplet). Coupling constants are reported as J value in Hz. Mass
spectrometry was obtained using a Q-TOF high resolution mass spectrometer. Elemental analyses
were performed with a Perkin Elmer 2400 Series II elemental analyzer instrument. Melting point was
recorded on a Chemiline CL-725 melting point apparatus and is uncorrected. Thin Layer
Chromatography (TLC) was performed using silica gel 60 F254 (Merck) plates.
General Procedure for the Synthesis of Functionalized(Z)-1-(aryl-1-acetoxymethylene)-2-
phenylhydrazines (3).
Aldehyde hydrazones (1; 0.25 mmol) and PhI(OCOCH3)2 or PhI(OCOCF3)2 (2; 0.25 mmol) were
carefully weighed into an oven-dried glass-vessel equipped with a magnetic stirrer bar and a tightly
screwed cap. Then 1,4-dioxane (1.5 mL) was added to the mixture, and stirred at ambient conditions
for stipulated time-frame (3-120 min) with occasional TLC monitoring to judge the progress of the
reaction. On completion of the reaction, 5 mL of EtOAc-H2O (4:1 v/v) was added to the resulting
mixture and shaken well. The organic layer was separated out, dried in sodium sulphate, and the
organic solvent was then removed under reduced pressure to obtain a crude mass, which was finally
purified by means of column chromatography using mixtures of EtOAc-hexane as eluents, to furnish
the desired acetoxylated product 3 (3-1 – 3-28). The structure of each compound was confirmed by
analytical as well as spectral studies including 1H-NMR, 13C-NMR, DEPT-135 and HRMS.
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The spectral and analytical data of all the compounds are given below:
(Z)-1-(1-acetoxy-1-(4-nitrophenyl)methylene)-2-phenylhydrazine (3-1). Yellow solid; yield: 95%

1
(71 mg; 0.25 mmol scale); mp = 185-186 C. H NMR (400 MHz, DMSO-d6):  = 11.89 (br s, 1H, -
NH), 8.37 (d, 2H, J = 8.0 Hz, Ar-H), 8.15 (d, 2H, J = 5.6 Hz, Ar-H), 7.48-7.39 (m, 4H, Ar-H), 7.24-
7.23 (m, 1H, Ar-H), 2.16 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz, DMSO-d6):  = 170.99 (ester
carbonyl), 164.29, 149.71, 141.17, 137.29, 129.13 (2C), 128.60 (2C), 127.12, 126.06, 123.84 (2C),
123.67, 21.68 (CH3CO) ppm. HRMS: m/z 322.0804 [M + Na]+ calcd for C15H13N3O4Na; Found: m/z
322.0824. Elemental analysis: calcd (%) for C15H13N3O4: C, 60.20; H, 4.38; N, 14.04; Found: C,
60.28; H, 4.33; N, 14.08.
(Z)-1-(1-acetoxy-1-phenylmethylene)-2-phenylhydrazine (3-2). Brown jelly mass; yield: 88% (56
1
mg; 0.25 mmol scale). H NMR (400 MHz, DMSO-d6):  = 11.59 (br s, 1H, -NH), 7.93 (d, 2H, J =
6.8 Hz, Ar-H), 7.65-7.61 (m, 1H, Ar-H), 7.56-7.63 (m, 2H, Ar-H), 7.48 (d, 2H, J = 7.6 Hz, Ar-H),
7.39-7.35 (m, 2H, Ar-H), 7.22-7.19 (m, 1H, Ar-H), 2.15 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz,
DMSO-d6):  = 171.31 (ester carbonyl), 165.74, 141.48, 132.53, 131.71, 128.78 (2C), 128.56 (2C),
127.56 (2C), 125.88, 123.54 (2C), 21.77 (CH3CO) ppm. Elemental analysis: calcd (%) for
C15H14N2O2: C, 70.85; H, 5.55; N, 11.02; Found: C, 70.89; H, 5.56; N, 11.07.
(Z)-1-(1-acetoxy-1-(3-nitrophenyl)methylene)-2-phenylhydrazine (3-3). Off white solid; yield:
94% (70 mg; 0.25 mmol scale); mp = 130-131 C. 1H NMR (400 MHz, CDCl3):  = 10.39 (br s, 1H, -
NH), 8.51 (br s, 1H, Ar-H), 8.23-8.06 (m, 2H, Ar-H), 7.53-7.37 (m, 6H, Ar-H), 2.10 (s, 3H, -CH3CO)
ppm. 13C NMR (100 MHz, CDCl3):  = 170.94, (ester carbonyl), 163.68, 148.13, 141.72, 133.39,
133.16, 129.79 (2C), 129.25, 127.85 (2C), 126.63, 125.32, 122.75, 22.27 (CH3CO) ppm. Elemental
analysis: calcd (%) for C15H13N3O4: C, 60.20; H, 4.38; N, 14.04; Found: C, 60.28; H, 4.39; N, 14.08.
(Z)-1-(1-acetoxy-1-(4-cyanophenyl)methylene)-2-phenylhydrazine (3-4). White solid; yield: 92%
(69 mg; 0.25 mmol scale); mp = 176-177C. 1H NMR (400 MHz, CDCl3):  = 10.26 (br s, 1H, -NH),
7.81 (d, 2H, J = 7.2 Hz, Ar-H), 7.55-7.49 (m, 4H,Ar-H),7.45-7.39 (m, 3H, Ar-H), 2.10(s, 3H, -
CH3CO) ppm. 13C NMR (100 MHz, CDCl3):  = 170.99 (ester carbonyl), 164.15, 141.72, 135.32,
132.28 (2C), 129.84 (2C), 129.31, 128.26 (2C), 127.80 (2C), 117.85 (CN), 115.62, 22.29 (CH3CO)
ppm. Elemental analysis: calcd (%) for C16H13N3O2: C, 68.81; H, 4.69; N, 15.05; Found: C, 68.89; H,
4.68; N, 15.03.
(Z)-1-(1-acetoxy-1-(4- trifluoromethylphenyl)methylene)-2-phenylhydrazine (3-5). White solid;
yield: 94% (76 mg; 0.25 mmol scale); mp = 111-112 C. 1H NMR (400 MHz, CDCl3):  = 10.48 (br s,
1H, -NH), 7.76 (d, 2H, J = 7.6 Hz, Ar-H), 7.52 (d, 2H, J = 7.2 Hz, Ar-H), 7.44-7.36 (m, 5H, Ar-H),
2.13 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz, CDCl3):  = 171.19 (ester carbonyl), 164.36,
141.87, 134.39, 129.82 (2C), 129.24, 127.95 (2C), 127.83 (2C), 125.48 (2C), 124.96, 122.25, 22.36
12
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10.1002/ejoc.201900994
European Journal of Organic Chemistry
(CH3CO) ppm. Elemental analysis: calcd (%) for C16H13F3N2O2: C, 59.63; H, 4.07; N, 8.69; Found: C,
59.69; H, 4.08; N, 8.67.
(Z)-1-(1-acetoxy-1-(2-fluorophenyl)methylene)-2-phenylhydrazine (3-6). White solid; yield: 90%

1
(61 mg; 0.25 mmol scale); mp = 133-134 C. H NMR (400 MHz, DMSO-d6):  = 11.47 (br s, 1H, -
NH), 7.71-7.68 (m, 1H, Ar-H), 7.64-7.61 (m, 1H, Ar-H), 7.47 (d, 2H, J = 7.6 Hz, Ar-H), 7.41-7.34
13
(m, 4H, Ar-H), 7.24-7.20 (m, 1H, Ar-H), 2.19 (s, 3H, -CH3CO) ppm. C NMR (100 MHz, DMSO-
d6):  = 170.99 (ester carbonyl), 163.33, 159.25 (JCF = 249 Hz), 141.18, 133.67 (JCF = 8 Hz), 130.11
(2C), 128.55 (2C), 125.88, 124.92, 123.39 (2C), 116.39 (JCF = 22 Hz), 21.78 (CH3CO) ppm.
Elemental analysis: calcd (%) for C15H13FN2O2: C, 66.17; H, 4.81; N, 10.29; Found: C, 66.22; H,
4.82; N, 10.26.
(Z)-1-(1-acetoxy-1-(4-fluorophenyl)methylene)-2-phenylhydrazine (3-7). Red solid; yield: 87%

1
(59 mg; 0.25 mmol scale); mp = 76-77 C. H NMR (400 MHz, CDCl3):  = 9.99 (br s, 1H, -NH),
7.86-7.73 (m, 2H, Ar-H), 7.50-7.19 (m, 5H, Ar-H), 7.06-6.89 (m, 2H, Ar-H), 2.07 (s, 3H, -CH3CO)
ppm. 13C NMR (100 MHz, CDCl3):  =170.86 (ester carbonyl), 165.78 (JCF = 122 Hz), 164.52 (JCF
=
130 Hz), 142.06, 130.09 (JCF = 9 Hz, 2C), 129.72 (2C), 129.02, 127.75 (2C), 124.97, 115.58 (JCF = 22
Hz, 2C), 22.32 (CH3CO) ppm. Elemental analysis: calcd (%) for C15H13FN2O2: C, 66.17; H, 4.81; N,
10.29; Found: C, 66.20; H, 4.80; N, 10.31.
(Z)-1-(1-acetoxy-1-(4-hydroxyphenyl)methylene)-2-phenylhydrazine (3-8). Brown solid; yield:

1
76% (51 mg; 0.25 mmol scale); mp = 193-194 C. H NMR (400 MHz, DMSO-d6):  = 11.29 (br s,
1H, -OH), 10.24 (br s, 1H, -NH), 7.80 (d, 2H, J = 8.0 Hz, Ar-H), 7.45 (d, 2H, J = 7.2 Hz, Ar-H), 7.37-
7.34 (m, 2H, Ar-H), 7.19 (t, 1H, J = 6.4 Hz, Ar-H), 6.87 (d, 2H, J = 8.4 Hz, Ar-H), 2.11 (s, 3H, -
13
CH3CO) ppm. C NMR (100 MHz, DMSO-d6):  = 171.38 (ester carbonyl), 165.22, 161.25, 141.63,
129.64 (2C), 128.43 (2C), 125.63, 123.35 (2C), 122.13, 115.24 (2C), 21.77 (CH3CO) ppm. Elemental
analysis: calcd (%) for C15H14N2O3: C, 66.66; H, 5.22; N, 10.36; Found: C, 66.71; H, 5.21; N, 10.39.
(Z)-1-(1-acetoxy-1-(4-methoxyphenyl)methylene)-2-phenylhydrazine (3-9). White amorphous;
yield: 93% (66 mg; 0.25 mmol scale); mp = 166-167 C. 1H NMR (400 MHz, CDCl3):  = 9.28 (br s,
1H, -NH), 7.72-7.61 (m, 2H, Ar-H), 7.41-7.39 (m, 2H, Ar-H), 7.29-7.19 (m, 3H, Ar-H), 6.78-6.65 (m,
2H, Ar-H), 3.69 (s, 3H, Ar-OCH3), 1.96 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz, CDCl3):  =
170.46 (ester carbonyl), 166.17, 162.81, 142.34, 129.56 (3C), 128.79, 127.76 (2C), 124.81, 123.90,
113.82 (2C), 55.51 (Ar-OCH3), 22.28 (CH3CO) ppm. Elemental analysis: calcd (%) for C16H16N2O3:
C, 67.59; H, 5.67; N, 9.85; Found: C, 67.62; H, 5.68; N, 9.83.
(Z)-1-(1-acetoxy-1-(3,4-dimethoxyphenyl)methylene)-2-phenylhydrazine (3-10). White solid;
yield: 93% (73 mg; 0.25 mmol scale); mp = 101-102 C. 1H NMR (400 MHz, CDCl3):  = 9.79 (br s,
1H, -NH), 7.52 (d, 2H, J = 6.8 Hz, Ar-H), 7.41-7.37 (m, 4H, Ar-H), 7.28 (br s, 1H, Ar-H), 6.69 (d,
13
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10.1002/ejoc.201900994
European Journal of Organic Chemistry
1H, J = 8.0 Hz, Ar-H), 3.86 (s, 3H, Ar-OCH3), 3.82 (s, 3H, Ar-OCH3), 2.11 (s, 3H, -CH3CO) ppm.
13C NMR (100 MHz, CDCl3):  = 170.85 (ester carbonyl), 165.83, 152.24, 148.67, 142.34, 129.67
(2C), 128.88, 127.80 (2C), 123.95, 120.89, 110.33, 110.22, 56.01 (Ar-OCH3), 55.91 (Ar-OCH3),
22.35 (CH3CO) ppm. Elemental analysis: calcd (%) for C17H18N2O4: C, 64.96; H, 5.77; N, 8.91;
Found: C, 64.99; H, 5.78; N, 8.89.
(Z)-1-(1-acetoxy-1-(3,4-methylenedioxyphenyl)methylene)-2-phenylhydrazine (3-11). White
solid; yield: 93% (69 mg; 0.25 mmol scale); mp = 169-170 C. 1H NMR (400 MHz, CDCl3):  = 9.79
(br s, 1H, -NH), 7.49-7.48 (m, 2H, Ar-H), 7.41-7.32 (m, 4H, Ar-H), 7.15 (br s, 1H, Ar-H), 6.65 (d,
1H, J = 8.0 Hz, Ar-H), 5.96 (br s, 2H,-OCH2O-), 2.07 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz,
CDCl3):  = 170.74 (ester carbonyl), 165.58, 150.93, 147.78, 142.21, 129.64 (2C), 128.86, 127.75,
125.62 (2C), 124.85, 122.65, 108.00, 101.81, 22.31 (CH3CO) ppm. Elemental analysis: calcd (%) for
C16H14N2O4: C, 64.42; H, 4.73; N, 9.39; Found: C, 64.47; H, 4.74; N, 9.41.
(Z)-1-(1-acetoxy-1-(4-methylphenyl)methylene)-2-phenylhydrazine (3-12). White solid; yield:
91% (61 mg; 0.25 mmol scale); mp = 127-128 C. 1H NMR (400 MHz, CDCl3):  = 9.08 (br s, 1H, -
NH), 7.73-7.67 (m, 2H, Ar-H), 7.49 (br s, 2H, Ar-H), 7.40-7.35 (br s, 3H, Ar-H), 7.22-7.12 (m, 2H,
Ar-H), 2.35 (s, 3H, Ar-CH3), 2.06 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz, CDCl3):  = 170.30
(ester carbonyl), 166.82, 142.89, 129.63 (2C), 129.31 (2C), 128.92, 127.77 (2C), 127.63 (2C), 127.02,
124.89, 22.20 (CH3CO), 21.61 (Ar-CH3) ppm. Elemental analysis: calcd (%) for C16H16N2O2: C,
71.62; H, 6.01; N, 10.44; Found: C, 71.66; H, 6.02; N, 10.40.
(Z)-1-(1-acetoxy-1-(3-formylphenyl)methylene)-2-phenylhydrazine (3-13). Pale yellow solid;

1
yield: 91% (64 mg; 0.25 mmol scale); mp = 152-153 C. H NMR (400 MHz, DMSO-d6):  = 11.79
(br s, 1H, -NH), 10.09 (s, 1H, Ar-CHO), 8.44 (br s, 1H, Ar-H), 8.23-8.15 (m, 2H, Ar-H), 7.79 (t, 1H, J
= 7.2 and 6.4 Hz, Ar-H), 7.48 (d, 2H, J = 6.0 Hz, Ar-H), 7.39-7.36 (m, 2H, Ar-H), 7.24-7.20 (m, 1H,
Ar-H), 2.16 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz, DMSO-d6):  = 192.66 (CHO), 171.12 (ester
carbonyl), 164.83, 141.33, 136.38, 133.18 (2C), 132.53, 129.76, 129.36, 128.56, 128.21, 127.05,
125.96, 123.64, 21.69 (CH3CO) ppm. Elemental analysis: calcd (%) for C16H14N2O3: C, 68.07; H,
5.00; N, 9.92; Found: C, 68.15; H, 5.04; N, 9.89.
(Z)-1-(1-acetoxy-1-(4-formylphenyl)methylene)-2-phenylhydrazine (3-14). Yellow solid; yield:

1
94% (66 mg; 0.25 mmol scale); mp = 124-125 C. H NMR (400 MHz, DMSO-d6):  = 11.78 (br s,
1H, -NH), 10.10 (s, 1H, Ar-CHO), 8.11-8.06 (m, 4H, Ar-H), 7.48 (d, 2H, J = 6.0 Hz, Ar-H), 7.39-7.37
13
(m, 2H, Ar-H), 7.23-7.20 (m, 1H, Ar-H), 2.16 (s, 3H, -CH3CO) ppm. C NMR (100 MHz, DMSO-
d6):  = 192.86 (CHO), 171.11 (ester carbonyl), 165.06, 141.29, 138.59, 136.62, 129.66 (2C), 128.59
(2C), 128.32 (2C), 127.11, 126.00, 123.64, 21.71 (CH3CO) ppm. Elemental analysis: calcd (%) for
C16H14N2O3: C, 68.07; H, 5.00; N, 9.92; Found: C, 68.11; H, 4.98; N, 9.88.
14
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10.1002/ejoc.201900994
European Journal of Organic Chemistry
(Z)-1-(1-acetoxy-1-styrylmethylene)-2-phenylhydrazine(3-15). Brown semi solid; yield: 87% (61
mg; 0.25 mmol scale). 1H NMR (400 MHz, DMSO-d6):  = 11.18 (br s, 1H, -NH), 7.68-7.64 (m, 3H,
Ar-H), 7.44-7.37 (m, 7H, Ar-H), 7.21(br s, 1H, olefinic H), 6.69 (d, 1H, J = 15.6 Hz, olefinic H) 2.11
13
(s, 3H, -CH3CO) ppm. C NMR (100 MHz, DMSO-d6):  = 171.11 (ester carbonyl), 164.62, 141.87
(olefinic C), 141.47, 134.25, 130.17, 129.01 (2C), 128.53 (2C), 127.92 (2C), 125.90, 123.58 (2C),
118.32 (olefinic C), 21.73 (CH3CO) ppm. Elemental analysis: calcd (%) for C17H16N2O2: C, 72.84; H,
5.75; N, 9.99; Found: C, 72.89; H, 5.76; N, 9.97.
(Z)-1-(1-trifluoroacetoxy-1-phenylmethylene)-2-phenylhydrazine (3-16). White amorphous; yield:

1
91% (70 mg; 0.25 mmol scale); mp = 189-190 C. H NMR (400 MHz, DMSO-d6):  = 11.97 (br s,
1H, -NH), 7.87 (d, 2H, J = 7.2 Hz, Ar-H), 7.68-7.64 (m, 1H, Ar-H), 7.58-7.55 (m, 4H, Ar-H), 7.50-
7.47 (m, 2H, Ar-H), 7.39-7.35 (m, 1H, Ar-H) ppm. 13C NMR (100 MHz, DMSO-d6):  = 166.35
(ester carbonyl), 156.54 (JCF = 35 Hz) 139.74, 132.89, 130.88, 129.51, 129.12, 128.87, 128.72,
127.91, 127.81, 127.56, 123.93 (CF3), 117.49, 114.62 ppm. HRMS: m/z 309.0851 [M + H]+ calcd for
C15H12F3N2O2; Found: m/z 309.0850. Elemental analysis: calcd (%) for C15H11F3N2O2: C, 58.45; H,
3.60; N, 9.09; Found: C, 58.48; H, 3.61; N, 9.07.
(Z)-1-(1-trifluoroacetoxy-1-(4-nitrophenyl)methylene)-2-phenylhydrazine
(3-17).
White
amorphous; yield: 92% (81 mg; 0.25 mmol scale); mp = 150-151 C. 1H NMR (400 MHz, CDCl3): 
= 12.37 (br s, 1H, -NH), 8.41 (d, 2H, J = 8.8 Hz, Ar-H), 8.09 (d, 2H, J = 9.2 Ar-H), 7.59-7.57 (m, 2H,
Ar-H), 7.52-7.48 (m, 2H, Ar-H), 7.41-7.37 (m, 1H, Ar-H) ppm. 13C NMR (100 MHz, CDCl3):  =
165.04 (ester carbonyl), 156.55, 149.99, 139.46, 136.30, 129.61, 129.23 (2C), 129.18, 128.15, 127.83,
124.11(CF3), 124.08, 117.43, 114.57 ppm. Elemental analysis: calcd (%) for C15H10F3N3O4: C, 51.00;
H, 2.85; N, 11.90; Found: C, 51.03; H, 2.84; N, 11.93.
(Z)-1-(1-acetoxy-1-phenylmethylene)-2-(4-fluorophenyl)hydrazine (3-18). Radish brown gum;
1
yield: 71% (48 mg; 0.25 mmol scale). H NMR (400 MHz, CDCl3):  = 11.58 (br s, 1H, -NH), 7.72
(d, 2H, J = 7.6 Hz, Ar-H), 7.64 (t, 1H, J = 7.2 Hz, Ar-H), 7.56-7.53 (m, 2H, Ar-H), 7.50-7.47 (m, 2H,
Ar-H), 7.21 (t, 2H, J = 8.8 and 8.4 Hz, Ar-H), 2.14 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz,
CDCl3):  = 171.30 (ester carbonyl), 165.64, 159.75 (JCF = 241 Hz), 137.77, 132.50, 131.57, 128.72
(2C), 127.51 (2C), 126.02 (JCF = 8 Hz, 2C), 115.23 (JCF = 22 Hz, 2C), 21.42 (CH3CO) ppm.
Elemental analysis: calcd (%) for C15H13FN2O2: C, 66.17; H, 4.81; N, 10.29; Found: C, 66.22; H,
4.82; N, 10.31.
(Z)-1-(1-acetoxy-1-phenylmethylene)-2-(4-chlorophenyl)hydrazine (3-19). Off white amorphous;

1
yield: 71% (51 mg; 0.25 mmol scale); mp = 165-166 C. H NMR (400 MHz, DMSO-d6):  = 11.61
(br s, 1H, -NH), 7.92 (d, 2H, J = 6.8 Hz, Ar-H), 7.66-7.63 (m, 1H, Ar-H), 7.57-7.53 (m, 2H, Ar-H),
7.49 (d, 2H, J = 8.4 Hz, Ar-H), 7.44-7.42 (m, 2H, Ar-H), 2.15 (s, 3H, -CH3CO) ppm. 13C NMR (100
15
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10.1002/ejoc.201900994
European Journal of Organic Chemistry
MHz, DMSO-d6):  = 171.38 (ester carbonyl), 165.67, 140.25, 132.58, 131.52, 129.76 (2C), 128.76
(2C), 128.50 (2C), 127.55 (2C), 124.97, 21.72 (CH3CO) ppm. Elemental analysis: calcd (%) for
C15H13ClN2O2: C, 62.40; H, 4.54; N, 9.70; Found: C, 62.43; H, 4.55; N, 9.71.
(Z)-1-(1-acetoxy-1-phenylmethylene)-2-(4-iodophenyl)hydrazine (3-20). Off white amorphous;

1
yield: 76% (72 mg; 0.25 mmol scale); mp = 198-199 C. H NMR (400 MHz, DMSO-d6):  = 11.59
(br s, 1H, -NH),7.91 (d, 2H, J = 6.8 Hz, Ar-H), 7.72(d, 2H, J = 7.6 Hz, Ar-H), 7.66-7.62 (m, 1H, Ar-
13
H), 7.55-7.53 (m, 2H, Ar-H), 7.29 (d, 2H, J = 8.8 Hz, Ar-H), 2.14 (s, 3H, - CH3CO) ppm. C NMR
(100 MHz, DMSO-d6):  = 171.32 (ester carbonyl), 165.63, 141.21, 137.31 (2C), 132.58, 131.51,
128.77 (2C), 127.55 (2C), 125.32 (2C), 90.44, 21.81 (CH3CO) ppm. HRMS: m/z 381.0022 [M + H]+
calcd for C15H14IN2O2; Found: m/z 381.0100. Elemental analysis: calcd (%) for C15H13IN2O2: C,
47.39; H, 3.45; N, 7.37; Found: C, 47.43; H, 3.46; N, 7.38.
(Z)-1-(1-acetoxy-1-phenylmethylene)-2-(2,3,4,5,6-pentafluorophenyl)hydrazine (3-21). White
amorphous; yield: 90% (77 mg; 0.25 mmol scale); mp = 153-154 C. 1H NMR (400 MHz, DMSO-d6):
 = 11.75 (br s, 1H, -NH), 7.89-7.86 (m, 2H, Ar-H), 7.65-7.61 (m, 1H, Ar-H), 7.55-7.51 (m, 2H, Ar-
H), 2.22 (s, 3H, - CH3CO) ppm. 13C NMR (100 MHz, DMSO-d6):  = 171.13 (ester carbonyl), 166.69
(JCF = 261 Hz), 165.19, 144.39 (JCF = 8 Hz), 141.88 (JCF = 8 Hz), 138.75 (JCF = 59 Hz), 136.06 (JCF
=
15 Hz), 132.61, 132.25, 131.25, 128.68, 128.47, 127.68, 115.69 (JCF = 3 Hz), 19.92 (CH3CO) ppm.
Elemental analysis: calcd (%) for C15H9F5N2O2: C, 52.34; H, 2.64; N, 8.14; Found: C, 52.38; H, 2.63;
N, 8.16.
(Z)-1-(1-acetoxy-1-(3,4,5-trimethoxyphenyl)methylene)-2-(2,3,4,5,6-pentafluorophenyl)

hydrazine (3-22). White amorphous; yield: 84% (91 mg; 0.25 mmol scale); mp = 177-178 C.
1H NMR (400 MHz, DMSO-d6):  = 11.65 (br s, 1H, -NH), 7.24 (s, 2H, Ar-H), 3.84 (s, 6H, 2 × Ar-
OCH3), 3.72 (s, 3H, Ar-OCH3), 2.22 (s, 3H, - CH3CO) ppm. 13C NMR (100 MHz, DMSO-d6):  =
171.15 (ester carbonyl), 166.34 (JCF = 344 Hz), 164.44, 152.80, 152.65, 144.43, 141.92, 141.23,
138.44, 135.98, 126.38, 125.95, 105.38 (2C), 60.12 (Ar-OCH3), 56.12 (2 × Ar-OCH3), 19.88
(CH3CO) ppm. HRMS: m/z 457.0799 [M + Na]+ calcd for C18H15F5N2O5Na; Found: m/z 457.0823.
Elemental analysis: calcd (%) for C18H15F5N2O5: C, 49.78; H, 3.48; N, 6.45; Found: C, 49.85; H, 3.51;
N, 6.48.
(Z)-1-(1-acetoxy-1-phenylmethylene)-2-(4-trifluoromethylphenyl)hydrazine (3-23). Off white

1
solid; yield: 93% (75 mg; 0.25 mmol scale); mp = 164-165 C. H NMR (400 MHz, DMSO-d6):  =
11.69 (br s, 1H, -NH), 7.95 (d, 2H, J = 7.6 Hz, Ar-H), 7.77-7.70 (m, 4H, Ar-H), 7.67-7.64 (m, 1H, Ar-
H), 7.58-7.55 (t, 2H, J = 7.6 and 7.2 Hz, Ar-H), 2.19 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz,
DMSO-d6):  = 171.63 (ester carbonyl), 165.72, 144.72, 132.65 (2C), 131.44, 128.80 (2C), 127.61
(3C), 125.87 (3C), 122.75 (CF3), 22.04 (CH3CO) ppm. HRMS: m/z 323.1007 [M + H]+ calcd for
16
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10.1002/ejoc.201900994
European Journal of Organic Chemistry
C16H14F3N2O2; Found: m/z 323.1002. Elemental analysis: calcd (%) for C16H13F3N2O2: C, 59.63; H,
4.07; N, 8.69; Found: C, 59.60; H, 4.06; N, 8.71.
(Z)-1-(1-acetoxy-1-phenylmethylene)-2-(4-trifluoromethoxyphenyl)hydrazine (3-24). Pale yellow

1
solid; yield: 75% (63 mg; 0.25 mmol scale); mp = 123-124 C. H NMR (400 MHz, DMSO-d6):  =
11.63 (br s, 1H, -NH), 7.93 (d, 2H, J = 6.8 Hz, Ar-H), 7.63-7.54 (m, 5H, Ar-H), 7.38 (d, 2H, J = 7.6
Hz, Ar-H), 2.16 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz, DMSO-d6):  = 171.47 (ester carbonyl),
165.71, 145.50, 140.38, 132.59, 131.49, 128.75 (2C), 127.57 (2C), 125.06 (2C), 121.30 (2C), 118.77,
21.66 (CH3CO) ppm. Elemental analysis: calcd (%) for C16H13F3N2O3: C, 56.81; H, 3.87; N, 8.28;
Found: C, 56.85; H, 3.89; N, 8.30.
(Z)-1-(1-acetoxy-1-(4-cyanophenyl)methylene)-2-(4-cyanophenyl)hydrazine
(3-25).
White
amorphous; yield: 97% (74 mg; 0.25 mmol scale); mp = 192-193 C. 1H NMR (400 MHz, DMSO-d6):
 = 11.92 (br s, 1H, -NH), 8.11-8.05 (m, 4H, Ar-H),7.84 (d, 2H, J = 8.4 Hz, Ar-H), 7.69 (d, 2H, J =
8.4 Hz, Ar-H), 2.19 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz, DMSO-d6):  = 171.30 (ester
carbonyl), 164.59, 144.91, 135.34, 133.02 (2C), 132.83 (2C), 128.54 (2C), 122.71, 118.57 (CN),
118.08 (CN), 114.95 (2C), 107.72, 22.17 (CH3CO) ppm. Elemental analysis: calcd (%) for
C17H12N4O2: C, 67.10; H, 3.97; N, 18.41; Found: C, 67.18; H, 3.96; N, 18.46.
(Z)-1-(1-acetoxy-1-(3-methylphenyl)methylene)-2-(3-methylphenyl)hydrazine
(3-26). White
amorphous; yield: 77% (54 mg; 0.25 mmol scale); mp = 95-96 C. 1H NMR (400 MHz, DMSO-d6): 
= 11.47 (br s, 1H, -NH), 7.73-7.69 (m, 2H, Ar-H), 7.43-7.42 (m, 2H, Ar-H), 7.28-7.24 (m, 3H, Ar-H),
7.03 (br s, 1H, Ar-H), 2.38 (s, 3H, Ar-CH3), 2.29 (s, 3H, Ar-CH3), 2.12 (s, 3H, -CH3CO) ppm.
13C NMR (100 MHz, DMSO-d6):  = 171.17 (ester carbonyl), 165.71, 141.47, 138.14, 137.74, 132.98,
131.71, 128.59, 128.34, 127.98, 126.56, 124.62, 124.24, 120.76, 21.68 (Ar-CH3), 21.97 (Ar-CH3),
20.86 (CH3CO) ppm. Elemental analysis: calcd (%) for C17H18N2O2: C, 72.32; H, 6.43; N, 9.92;
Found: C, 72.38; H, 6.46; N, 9.85.
(Z)-1-(1-acetoxy-1-(2-naphthyl)methylene)-2-phenylhydrazine (3-27). Pale pink solid ; yield: 99%

1
(75 mg; 0.25 mmol scale); mp = 165-166 C. H NMR (400 MHz, DMSO-d6):  = 11.71 (br s, 1H, -
NH), 8.56 (br s, 1H, Ar-H), 8.09-8.06 (m, 2H, Ar-H), 8.01 (d, 1H, J = 7.6 Hz, Ar-H), 7.96 (d, 1H, J =
8.0 Hz, Ar-H), 7.68-7.61 (m, 2H, Ar-H), 7.52 (d, 2H, J = 7.6 Hz, Ar-H), 7.41-7.37 (m, 2H, Ar-H),
7.24-7.20 (m, 1H, Ar-H), 2.19 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz, DMSO-d6):  = 171.25
(ester carbonyl), 165.79, 141.51, 134.55, 132.00, 128.94 (2C), 128.50, 128.37 (2C), 128.18, 127.67
(2C), 127.01, 125.81, 123.84 (2C), 123.56, 21.74 (CH3CO) ppm. 13C NMR (100 MHz, DMSO-
d6):  = 171.29 (ester carbonyl), 165.83, 141.48, 134.61, 132.03, 129.42, 129.35, 129.01 (2C), 128.56,
128.46, 128.28, 127.74 (2C), 127.10, 125.87, 123.88, 123.58, 21.81 (CH3CO) ppm. Elemental
analysis: calcd (%) for C19H16N2O2: C, 74.98; H, 5.30; N, 9.20; Found: C, 75.02; H, 5.28; N, 9.24.
17
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10.1002/ejoc.201900994
European Journal of Organic Chemistry
(Z)-1-(1-acetoxy-1-(2-thienyl)methylene)-2-phenylhydrazine (3-28). Pale brownish yellow solid;
yield: 97% (63 mg; 0.25 mmol scale); mp = 98-100C. 1H NMR (400 MHz, DMSO-d6):  = 11.58 (br
s, 1H, -NH), 7.91 (br s, 2H, Ar-H), 7.46-7.44 (m, 2H, Ar-H), 7.39-7.38 (m, 2H, Ar-H), 7.24-7.21 (m,
2H, Ar-H), 2.14 (s, 3H, -CH3CO) ppm. 13C NMR (100 MHz, DMSO-d6):  = 171.23 (ester carbonyl),
160.52, 141.41, 135.86, 132.72, 129.87, 129.30, 128.54, 128.32, 127.00, 125.90, 123.48, 21.68
(CH3CO) ppm. Elemental analysis: calcd (%) for C13H12N2O2S: C, 59.98; H, 4.65; N, 10.76; Found:
C, 60.13; H, 4.66; N, 10.72.
ASSOCIATED CONTENT
Supporting Information
Synthesis and characterization data for all the starting aldehyde hydrazones (1-1 – 1-26) along with
1
13
scanned copies of their respective H NMR and C NMR spectra are supplemented. Scanned copies
of respective 1H NMR and 13C NMR spectra for all the synthesized compounds (3-1 – 3-28) and HR-
MS for selected compounds (3-1, 3-16, 3-20, 3-22, 3-23) are also documented in the Supporting
Information.
Conflicts of interest
There are no conflicts of interest to declare.
Acknowledgements
Financial support from the Science and Engineering Research Board (SERB), Department of Science
& Technology (DST), Government of India, New Delhi is gratefully acknowledged. IK is thankful to
the UGC, New Delhi for awarding him senior research fellowship. The authors are also thankful to
DST-FIST Programme, and Department of Chemistry, Visva-Bharati University for infrastructural
facilities.
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