KF/Nano-clinoptilolite Catalyzed Aldol-Type Reaction of Aldehydes with Ethyl Diazoacetate

Article abstract of DOI:10.1007/s10562-017-2158-6

Abstract: Potassium fluoride supported on nano-clinoptilolite (KF/CP NPs) was used as an excellent catalytic system for direct aldol-type condensation of aldehydes with ethyl diazoacetate under solvent-less conditions. A variety of α-diazo carbonyl derivatives were prepared in good to excellent yields in short reaction times. Graphical Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-017-2158-6

Catal Lett
DOI 10.1007/s10562-017-2158-6
KF/Nano-clinoptilolite Catalyzed Aldol-Type Reaction
of Aldehydes with Ethyl Diazoacetate
Javad Balou1 · Mohammad A. Khalilzadeh1,2 · Dariush Zareyee1
Received: 1 June 2017 / Accepted: 30 July 2017
© Springer Science+Business Media, LLC 2017
Abstract Potassium fluoride supported on nano-clinop-
tilolite (KF/CP NPs) was used as an excellent catalytic sys-
tem for direct aldol-type condensation of aldehydes with
ethyl diazoacetate under solvent-less conditions. A variety
of α-diazo carbonyl derivatives were prepared in good to
excellent yields in short reaction times.
Graphical Abstract
Keywords KF/nano-clinoptilolite · Aldol-type reaction ·
Ethyl diazoacetate · α-Diazo carbonyl derivatives
1 Introduction
Diazo compounds have received considerable attention
in recent years due to their wide applications in synthetic
organic chemistry [1], among which α-diazo carbonyl
derivatives are the most fundamental chemicals as they are
usually the starting materials for the synthesis of other use-
ful organic chemicals [2, 3]. These compounds are useful
intermediates in the synthesis of amino alcohols and amino
acids. α-Diazo carbonyl compounds are readily obtained
from the corresponding aldehyde derivatives upon treat-
ment with acyldiazomethanes, generally by deprotona-
tion of the acyldiazomethane in the presence of a strong
base catalyst. A large number of base catalysts have been
reported to effect the condensation of acyldiazomethanes
with aldehydes including lithium diisopropylamide (LDA)
[4, 5], sodium hydride [6], potassium hydroxide [7, 8] and
quaternary ammonium hydroxide [9]. Although the gener-
ated anionic species can efficiently react with aldehydes to
afford α-diazo-β-hydroxy carbonyl compounds, the strong
* Mohammad A. Khalilzadeh
mkhalil3@ncsu.edu
1
Department of Chemistry, Qaemshahr Branch, Islamic Azad
University, Qaemshahr, Iran
2
Department of Biomaterials, College of Natural Resources,
North Carolina State University, Raleigh, USA
Vol.:(0123456789)
1 3

J. Balou et al.
Table 1 Effect of various bases for the addition of EDA to benzal-
organic transformations [23–28]. KF/CP exhibits a greatly
enhanced basicity compared to the potassium fluoride.
This property can be boosted when CP nanoparticles were
used, as the large surface areas of such particles provides
enhanced catalytic activities [29].
dehyde
In the past decade, green chemistry has attracted much
attention, and it currently encompasses major areas of the
chemical sciences. The recent increase of environmental
consciousness towards clean technology emphasizes the
point that the best solvent is no solvent. Solvent-free reac-
tions have many benefits that are reduced pollution, lower
costs and the simplicity of the processes. In continuation
of our ongoing program to develop green synthetic proto-
cols, we here report a simple, green, and selective proto-
col for the synthesis of α-diazo carbonyl compounds using
catalytic amounts of KF/CP NPs as an efficient solid base
catalyst [29, 30].
Entry
Base (mol%)
Time (h)
Yield (%)a
1
2
3
4
5
6
7
8
NaOH (20)
KOH (20)
8
5
10
12
8
10
5
12
24
12
5
50
51
45
38
42
5<
56
30
0
trace
86
85c
67
K2CO3 (20%)
Na2CO3 (20%)
KF (20%)
CPb
KF/CP (20%)
CaH2 (20%)
–
K3PO4 (20%)
KF/CP NPs (20%)
KF/CP NPs (15%)
KF/CP NPs (10%)
9
2 Results and Discussion
10
11
12
13
To confirm the catalytic activity of KF/CP NPs, various
solid bases were studied for the preparation of ethyl-2-di-
azo-3-hydroxy-3-phenylpropionate (3a) by the reaction of
benzaldehyde (1a) with ethyl diazoacetate (2) at room tem-
perature under solvent-free conditions, and the results are
summarized in Table 1.
5
5
Benzaldehyde (1 mmol), EDA (1.2 mmol), at room temperature
aYield by NMR
b0.1 g of CP was used
cAverage of two runs
Potassium hydroxide shows better catalytic performance
at shorter reaction time than other bases such as NaOH,
K2CO3 and Na2CO3 (Table 1, entries 1–4). Potassium fluo-
ride alone afforded only low yield of product 3a (Table 1,
entry 5). The reaction mediated clinoptilolite afforded less
than 5% of desired product (Table 1, entry 6). Potassium
fluoride supported on clinoptilolite afforded moderate yield
of desired product (Table 1, entry 7). Only 30% of product
3a was formed when CaH2 was used as catalyst (Table 1,
entry 8). No addition product was obtained when the reac-
tion carried out without catalyst (Table 1, entry 9), even
after prolonged reaction time. Only trace of product was
formed when K3PO4 was used as catalyst (Table 1, entry
10). However, the outcome of reaction was significantly
enhanced when 20% of KF/CP NPs was used as catalyst
(Table 1, entry 11). Reducing the amounts of catalyst to
15 mol% did not affect the outcome of reaction and product
3a was obtained in 85% yield after 5 h (Table 1, entry 12).
However, decreasing the catalyst loading to 10 mol% led to
a substantial decrease in the yield of 3a (Table 1, entry 13).
Thus 15 mol% of KF/CP NPs was chosen for subsequent
substrates.
basic reaction medium makes these reactions less attractive
for synthetic organic chemists. The use of Lewis bases like
1,8-diazobicyclo-[5.4.0]undec-7-ene (DBU) enables the
same transformation under milder conditions [10, 11]. In
addition, various efficient catalytic systems in water includ-
ing pyrrolidine [12], DBU [13], KOtBu [14], ionic liquids
[15, 16], KOtBu under solvent-free conditions [17, 18] and
DBU/flow conditions [19] have been developed as a green
alternative to the traditional organic solvents. Heterogene-
ous base catalysts have also shown great potential as cat-
alysts for this transformation. Kantam et al. reported that
ethyl diazoacetate (EDA) can be condensed with a range
of aromatic aldehydes in the presence of magnesium/lan-
thanum mixed oxide to afford the desired products in rea-
sonable yields [20, 21]. The same authors later utilized
silica-supported tetramethylguanidine catalyst to the reac-
tion of EDA with divers aldehydes, leading to the improve-
ment of yields with shorter reaction times [22]. The use of
a solid catalyst allows replacement of the soluble homo-
geneous catalysts, contributing to a reduction of waste to
conform to the concept of green technology. Recently, we
have developed a simple catalytic system using potassium
fluoride impregnated on clinoptilolite (KF/CP) in various
The efficiency of the condensation involving the KF/CP
NPs was examined with a series of aldehydes 1 and ethyl
diazoacetate 2 under solvent-free conditions at room tem-
perature (Table 2).
1 3

KF/Nano-clinoptilolite Catalyzed Aldol-Type Reaction of Aldehydes with Ethyl Diazoacetate
Table 2 KF/CP NPs-catalyzed synthesis of α-diazo carbonyl com-
The reaction is efficient for variety of aliphatic and aro-
matic aldehydes, giving α-diazo carbonyl compounds in
moderate to high yields. Both electron-rich and electron-
deficient aldehydes worked well, affording the desired
products in good to high yields. Electron-deficient alde-
hydes gave relatively higher yields than their electron-rich
counterparts (Table 2). Heterocyclic aldehydes, such as fur-
fural and 2-pyridinecarboxaldehyde produced correspond-
ing products 3h and 3i in good yields. However, aliphatic
aldehydes gave comparatively lower yields than aromatic
aldehydes. α,β-Unsaturated aldehydes such as cinnamalde-
hyde also gave good yields of product. The effect of tem-
perature on the outcome of the reaction has been investi-
gated. Interestingly, heating the reaction to 80 °C led to the
formation of substantial amounts of ethyl 2-benzoylacetate
4 through the intermediate 3a (Scheme 1).
pounds
Yield (%)a
Time (h) Product
Entry
Aldehyde
1
85
77
4
3
3a
3b
2
Clinoptilolite nanoparticles have been easily prepared by
grinding in a planetary ball mill using a zirconia vial set
under dry conditions with a time period of about 20 min.
The KF/CP NPs catalyst was then prepared according to
previously reported procedure. The particle size and mor-
phology of CP NPs and KF@CP NPs samples have been
analyzed by SEM and TEM. The SEM images showed
polydisperse of morphology and wide range of particle
size distributions (Fig. 1). These features are influenced
by milling process and thus can be varied. Although, the
TEM images showed some particles with micro-dimension
but the major particles are formed in smaller sizes with
spherical shapes in about 35–65 nm size range. The TEM
images of the KF@CP NPs samples show the KF@CP
NPs are rather dispersed relative to CP NPs. This could be
explained by adsorption of potassium fluoride onto the CP
NPs that increase the negative charges resulted from free
fluoride anions on the surface of zeolite leading the electro-
static repulsion between the layers.
3
3
80
3c
4
5
6
3
4
5
87
78
60
3d
3e
3f
7
8
9
4
4
4
72
70
78
3g
3h
3i
A plausible reaction mechanism of the present fluoride-
catalyzed aldol-type condensation has shown in Scheme 2.
The reaction involves the abstraction of the proton from
EDA to generate a carbanion stabilized by potassium cap-
tured in the nano-CP. The EDA carbanion would react with
aldehydes to release the product upon protonation with HF
formed due to the abstraction of protons.
10
11
5
5
50b
55b
3j
3k
12
13
6
3
52b
70b
3l
In order to show the merit of this method, the yield of
the reaction of ethyl diazoacetate and benzaldehyde has
been compared with some other protocols using different
catalysts and conditions (Table 3).
3m
14
4
72
3n
It is clear that KF/CP nano particles can efficiently cata-
lyze the synthesis of ethyl 2-diazo-3-hydroxy-3-phenyl-
propanoate (3a) and it is comparable to previous reported
methods, however, the present method benefits from cheap-
ness and catalyst recovery.
Reaction conditions benzaldehyde (1 mmol), EDA (1.2 mmol), KF/
CP NPs (15–20 mol%), at room temperature
aIsolated yield
bReactions performed using 20 mol% of KF/CP NPs
The reusability of the catalyst was also investigated. The
used KF/CP NPs, obtained after filtration from the reaction
1 3

J. Balou et al.
OH
O
O
O
O
CHO
KF/CP NPs
H
+
OEt
OEt
OEt
Solvent-free/80 °C
4h
N2
3a
N2
1a
2
4 (55%)
Scheme 1 Direct formation of ethyl 2-benzoylacetate in the presence of KF/CP NPs at 80 °C
Fig. 1 SEM (a) and TEM (b) images of CP NPs. TEM image of KF/CP NPs (c)
Scheme 2 A plausible mecha-
nism for aldol-type condensa-
tion of aldehydes with ethyl
diazoacetate in the presence of
KF/CP NPs
H
R
H
O-
F- K+
O
O
OH
O
O
F- K+
+
H
F- K+
EtO
R
OEt
R
OEt
N
N
N
N
N
N
100
80
60
40
20
0
Table 3 Comparison among synthesis of ethyl 2-diazo-3-hydroxy-
3-phenylpropanoate (3a) from the reaction of benzaldehyde with
ethyl diazoacetate using various catalysts and conditions
Entry Conditions
Time (h) Catalyst
Yield%
1 [20] Water/rt
2 [15] Water/rt
3 [17] Solvent-free/rt
4 [10] MeCN/rt
5 [13] water/rt
6 [12] Water/rt
7 [22] DMSO/rt
8 [21] DMSO/rt
7
6
2
8
24
2
2
2
4
Mg/La mixed oxide 85
1
2
3
4
5
MR-IMZ-OH
tert-BuOK
DBU
90
87
78
74
65
90
78
85
No. of cycles
Fig. 2 Reusability of KF/CP NPs for the condensation of EDA with
DBU
benzaldehyde
pyrrolidine
SiO2-TMG
NAP-MgO
KF/CP NPs
mixture was thoroughly washed with dry ethyl acetate,
dried under vacuum and reused again for the condensa-
tion of EDA with benzaldehyde. The recyclability of the
9
Solvent-free/rt
1 3

KF/Nano-clinoptilolite Catalyzed Aldol-Type Reaction of Aldehydes with Ethyl Diazoacetate
catalyst was confirmed when it was found to exhibit good
activity even after the five run without significant decrease
in the yield (Fig. 2).
separated by filtration from the product solution and the
filtrate washed further with dry ethyl acetate. The solvent
of residue was removed under reduced pressure. The crude
product was purified by column chromatography on silica
gel. The products were characterized by the use of spec-
tral data and comparison of their physical data with the
literature.
In conclusion, we have developed a convenient and effi-
cient method for the preparation of β-hydroxy-α-diazo car-
bonyl compounds by the condensation of aldehydes with
ethyl diazoacetate using KF/CP NPs as a heterogeneous
catalyst under solvent-less conditions at room temperature.
The catalyst can be easily recovered and reused for next run
without significant loss of catalytic activity. This method-
ology offers significant improvements for the synthesis of
β-hydroxy-α-diazo carbonyls with regard to yield of prod-
ucts, cost efficiency, simplicity in operation, and green
aspects by avoiding toxic catalysts and solvents.
3.2.1 Ethyl‑2‑diazo‑3‑hydroxy‑3‑phenylpropanoate (3a)
[31]
1H NMR (400 MHz, CDCl3) δ: 1.28 (t, J=7.1, 3H), 3.48
(bs, 1H), 4.24 (q, J=7.1 Hz, 2H), 5.83 (s, 1H), 7.28–7.43
(m, 5H); 13C NMR (100 MHz, CDCl3) δ: 14.5, 61.2, 68.7,
125.7, 128.3, 128.7, 139.0, 166.6.
3 Experimental Section
3.2.2 Ethyl‑2‑diazo‑3‑hydroxy‑3‑(4‑chlorophenyl)‑pro‑
All chemicals used in this work were purchased from
Merck and Sigma and were used without further purifica-
tion. Clinoptilolite was obtained from Afrandtooska Com-
pany in the region of Semnan. The morphology of nano-
particles of KF/clinoptilolite was characterized by scanning
electron microscopy (SEM) using a Holland Philips XL30
microscope. Transmission electron microscopy (TEM) was
carried out using a Zeiss EM10C microscope at 80 KV.
panoate (3b) [31]
1H NMR (400 MHz, CDCl3) δ: 1.27 (t, J=7.1, 3H),
4.19–4.27 (m, 3H), 5.76 (d, J=4.3 Hz, 1H), 7.36–7.44
(m, 4H); 13C NMR (100 MHz, CDCl3) δ: 14.4, 61.5, 67.9,
127.2, 128.9, 134.1, 137.6, 166.4.
1
The H NMR (400 MHz) and 13C NMR (100 MHz) were
3.2.3 Ethyl‑3‑hydroxy‑2‑diazo‑3‑(2‑chlorophenyl)‑pro‑
panoate (3c) [31]
measured with a Bruker AVANCE-DRX. FT-NMR spec-
1
trometer (δ in ppm). H and 13C spectra were obtained for
1H NMR (400 MHz, CDCl3) δ: 7.71 (m, 1H), 7.25–7.39
(m, 3H), 6.12 (s, 1H), 4.27 (q, J=7.0 Hz, 2H), 3.48 (bs,
1H), 1.29 (t, J=7.0 Hz, 3H); 13C NMR (100 MHz, CDCl3)
δ: 14.3, 61.3, 66.2, 127.1, 127.3, 129.2, 129.4, 131.6,
136.5, 166.4.
solutions in CDCl3 using TMS as internal standard.
3.1 Preparation of KF/CP NPs
Nano-sized natural clinoptilolite zeolite was prepared by
grinding in a planetary ball mill using a zirconia vial set in
dry conditions with a time period of about 20 min. The KF/
CP NPs catalyst was prepared according to our previously
reported procedure [28]. Thus, 1 g of KF was dissolved in
distilled water (10 ml) and nano-clinoptilolite (9 g). The
mixture was stirred for an hour and then, the water was
evaporated at 60–70 °C under reduced pressure and further
dried at 70–80 °C in a vacuum drying oven for 30 h. The
dried material was powdered using a mortar and pestle and
stored in a desiccator until use.
3.2.4 Ethyl 2‑diazo‑3‑(4‑fluorophenyl)‑3‑hydroxypro‑
panoate (3d) [31]
1H NMR (400 MHz, CDCl3) δ: 1.26 (t, J=7.12 Hz,
3H), 3.60 (s, 1H), 4.21 (q, J=7.12 Hz, 2H), 5.88 (s,
1H), 7.05–7.08 (m, 2H), 7.40–7.43 (m, 2H); 13C NMR
(100 MHz, CDCl3) δ: 14.5, 61.3, 68.1, 115.6, 127.5, 134.9,
161.3, 163.7, 166.4.
3.2 General Procedure for the Synthesis of Compounds
3a–n
3.2.5 Ethyl 2‑diazo‑3‑(4‑methylphenyl)‑3‑hydroxypro‑
panoate (3e) [31]
1H NMR (400 MHz, CDCl3) δ: 1.28 (t, J=7.1 Hz, 3H),
2.35 (s, 3H), 3.42 (s, 1H), 4.25 (q, J=7.1 Hz, 2H), 5.88 (s,
A mixture of aldehyde (1 mmol), ethyl diazoacetate
(1.2 mmol), and KF/CP NPs (15–20 mol%) was stirred at
room temperature for the time indicated in Table 2. The
progress of reaction was monitored by TLC. Upon com-
pletion, dry ethyl acetate was added and the catalyst was
1H), 7.18 (d, J=8.0 Hz, 2H), 7.30 (d, J=8.0 Hz, 2H); 13
C
NMR (100 MHz, CDCl3) δ: 14.5, 21.1, 61.2, 68.5, 125.7,
129.4, 135.5, 138.2, 166.5.
1 3

J. Balou et al.
3.2.6 Ethyl‑2‑diazo‑3‑hydroxy‑3‑(4‑methoxyphenyl)pro‑
4.25 (q, 7.2 Hz, 2H), 4.63–4.69 (m, 1H); 13C (100 MHz,
CDCl3) δ: 13.9, 14.4, 22.3, 27.7, 33.7, 61.0, 66.6, 166.7.
panoate (3f) [31]
1H NMR (400 MHz, CDCl3) δ: 1.29 (t, J = 7.2, 3H), 3.18
(s, 1H), 3.79 (s, 3H), 4.24 (q, J = 7.2 Hz, 2H), 5.86 (s,
1H), 6.90 (d, J = 8.3 Hz, 2H), 7.30 (d, J = 8.3 Hz, 2H);
13C NMR (100 MHz, CDCl3) δ: 14.5, 55.3, 61.2, 68.3,
114.1, 127.0, 131.1, 159.4, 166.5.
3.2.12 Ethyl‑2‑diazo‑3‑hydroxy‑4‑methylpentanoate (3l)
[15]
1H NMR (400 MHz, CDCl3) δ: 0.95 (d, 3H, J=6.8 Hz),
1.07 (d, J=6.9 Hz, 3H), 1.29 (t, J=7.8 Hz), 1.84–1.94
(m, 1H), 2.57 (bs, 1H), 4.20–4.28 (m, 3H); 13C NMR
(100 MHz, CDCl3) δ: 14.4, 18.7, 18.8, 32.7, 60.9, 72.2,
166.7.
3.2.7 Ethyl‑2‑diazo‑3‑hydroxy‑3‑(3‑methoxyphenyl)pro‑
panoate (3g) [32]
3.2.13 Ethyl‑3‑cyclohexyl‑2‑diazo‑3‑hydroxypropanoate
1H NMR (400 MHz, CDCl3): δ 1.29 (t, J = 7.3 Hz, 3H),
3.82 (s, 3H), 3.05 (s, 1H), 4.27 (q, J = 7.3 Hz, 2H), 5.89
(s, 1H), 6.83 (m, 1H), 7.05–6.97 (m, 2H), 7.28–7.36 (m,
1H); 13C NMR (100 MHz, CDCl3) δ: 14.4, 55.2, 61.2,
68.6, 111.1, 113.8, 117.9, 129.9, 140.5, 159.9, 166.5.
(3m) [15]
1H NMR (400 MHz, CDCl3) δ: 0.93–1.27 (m, 9H),
1.51–1.76 (m, 4H), 1.99–2.01 (m, 1H), 3.02 (s, 1H), 4.17
(q, J=7.11 Hz, 2H), 4.25 (d, J=8.57 Hz, 1H); 13C NMR
(100 MHz, CDCl3) δ: 14.5, 25.7, 26.3, 29.2, 42.1, 61.0,
71.3, 166.9.
3.2.8 Ethyl‑2‑diazo‑3‑(furan‑2‑yl)‑3‑hydroxypropanoate
(3h) [20]
3.2.14 Ethyl‑2‑diazo‑3‑hydroxy‑5‑phenylpent‑4‑enoate
(3n) [31]
1H NMR (400 MHz, CDCl3) δ: 1.27 (t, J = 7.12 Hz,
3H), 3.40 (s, 1H), 4.24 (q, J = 7.12 Hz, 2H), 5.80 (s,
1H), 6.33–6.38 (m, 2H), 7.38–7.35 (m, 1H); 13C NMR
(100 MHz, CDCl3) δ: 14.4, 61.3, 63.4, 107.5, 110.4,
142.8, 152.1, 166.1.
1H NMR (400 MHz, CDCl3) δ: 1.28 (t, J=7.1, 3H), 2.83
(bs, 1H), 4.26 (q, J=7.1 Hz, 2H), 5.43–5.55 (m, 1H),
6.21 (dd, J=15.8, 5.4 Hz, 1H), 6.79 (d, J=15.8 Hz, 1H),
7.22–7.40 (m, 5H); 13C NMR (100 MHz, CDCl3) δ: 14.4,
61.1, 66.8, 114.2, 126.1, 126.7, 128.5, 131.8, 135.1, 166.2.
3.2.9 Ethyl‑2‑diazo‑3‑hydroxy‑3‑(2‑pyridinyl)‑propanoate
3.2.15 Ethyl‑2‑benzoylacetate (4) [34]
(3i) [20]
1H NMR (400 MHz, CDCl3) δ: 1.25 (t, J=7.1 Hz, 3H),
3.98 (s, 2H), 4.20 (q, J=7.1 Hz, 2H), 7.43–7.95 (m, 5H);
13C NMR (100 MHz, CDCl3) δ: 14.1, 46.0, 61.5, 128.4,
128.6, 133.7, 136.0, 167.6, 192.7.
1H NMR (400 MHz, CDCl3) δ: 1.29 (t, J = 7.1 Hz, 3H),
4.24 (q, J = 7.1 Hz, 2H), 5.80 (s, 1H), 7.24–7.27 (m, 1H),
7.43 (d, J = 8.1 Hz, 1H), 7.73 (t, J = 8.0 Hz, 1H) 8.53 (d,
J = 8.1 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ: 14.6,
61.1, 67.3, 121.1, 123.3, 137.1, 148.1, 158.1, 166.1.
References
3.2.10 Ethyl‑2‑diazo‑3‑hydroxy‑pentanoate (3j) [33]
1. Bug T, Hartnagel M, Schlierf C, Mayr H (2003) Chemistry
9:4068
1H NMR (400 MHz, CDCl3) δ: 1.02 (t, J = 7.8 Hz, 3H)
1.32 (t, J = 7.0 Hz, 3H), 1.69–1.55 (m, 2H), 1.83–1.57 (m,
3H), 2.83 (bs, 1H), 4.24 (q, J = 7.8 Hz, 2H), 4.67–4.58
(m, 1H); 13C NMR (100 MHz, CDCl3) δ: 9.9, 14.5, 27.1,
27.8, 60.9, 68.1.
2. Ford A, Miel H, Ring A, Slattery CN, Maguire AR, McKervey
MA (2015) Chem Rev 115:9981
3. Liao M, Yao W, Wang J (2004) Synthesis 2633:2636
4. Pellicciari R, Natalini B, Sadeghpour BM, Marinozzi M, Snyder
JP, Williamson BL, Kuethe JT, Padwa A (1996) J Am Chem Soc
118:1
5. Moody CJ, Taylor RJ (1987) Tetrahedron Lett 28:5351
6. Jiang N, Qu Z, Wang J (2001) Org Lett 3:2989
7. Wenkert E, McPherson CA (1972) J Am Chem Soc 94:8084
8. Woolsey NF, Khalil MH (1972) J Org Chem 37:2405
9. Varala R, Enugala R, Nuvula S, Adapa SR (2006) Tetrahedron
Lett 47:877
3.2.11 Ethyl‑2‑diazo‑3‑hydroxyheptanoate (3k) [15]
1H NMR (400 MHz, CDCl3) δ: 0.89 (t, J = 7.1 Hz, 3H),
1.29 (t, J = 7.1 Hz, 3H), 1.30–1.77 (m, 6H), 2.62 (bs, 1H),
10. Jiang N, Wang J (2002) Tetrahedron Lett 43:1285
11. Erhunmwunse MO, Steel PG (2008) J Org Chem 73:8675
1 3

KF/Nano-clinoptilolite Catalyzed Aldol-Type Reaction of Aldehydes with Ethyl Diazoacetate
12. Kantam ML, Chakrapani L, Ramani T, Reddy KR (2010) Synth
Commun 40:1724
24. Keipour H, Hosseini A, Khalilzadeh MA, Ollevier T (2015) Lett
Org Chem 12:645
13. Xiao F, Liu Y, Wang J (2007) Tetrahedron Lett 48:1147
14. Sreedhar B, Balasubrahmanyam V, Sridhar C, Nagendra Prasad
M (2005) Catal Commun 6:517
25. Keipour H, Khalilzadeh MA, Hosseini A, Pilevar A, Zareyee D
(2012) Chin Chem Lett 23:537
26. Salmanpour S, Khalilzadeh MA, Hosseini A (2013) Comb Chem
High Throughput Screen 16:339
15. Likhar P, Roy S, Roy M, Subhas M, Kantam M (2009) Catal
Commun 10:728
27. Khalilzadeh MA, Keipour H, Hosseini A, Zareyee D (2014) New
J Chem 38:42
16. Miraki MK, Mehraban JA, Yazdani E, Heydari A (2017) J Mol
Liq 234:129
28. Khalilzadeh MA, Hosseini A, Pilevar A (2011) Eur J Org Chem
2011:1587
17. Chen S, Yuan F, Zhao H, Li B (2013) RSC Adv 3:12616
18. Chen S, Du Y, Zhao H, Li B (2014) RSC Adv 4:12482
19. Müller STR, Smith D, Hellier P, Wirth T (2014) Synlett 25:871
20. Kantam ML, Balasubrahmanyam V, Kumar KBS, Venkanna GT,
Figueras F (2007) Adv Synth Catal 349:1887
21. Kantam ML, Chakrapani L, Ramani T (2007) Tetrahedron Lett
48:6121
29. Sajjadi-Ghotbabadi H, Javanshir S, Rostami-Charati F (2016)
Catal Lett 146:338
30. Hallajian S, Khalilzadeh M A, Tajbakhsh M, Alipour E, Safaei Z
(2015) Comb Chem High Throughput Screen 18:486
31. Maurya RA, Min K-I, Kim D-P (2014) Green Chem 16:116
32. Trost BM, Malhotra S, Fried BA (2009) J Am Chem Soc
131:1674
22. Likhar P, Roy S, Roy M, Subhas M, Kantam M (2008) Synlett
2008:1283
33. Trost BM, Malhotra S, Koschker P, Ellerbrock P (2012) J Am
Chem Soc 134:2075
23. Keipour H, Hosseini A, Afsari A, Oladee R, Khalilzadeh MA,
Ollevier T (2016) Can J Chem 94:95
34. Huang P-Q, Ou W (2017) Eur J Org Chem 2017:582
1 3