Lithiation of N,N,N′,N′-tetraisopropylpyridine-2,6- dicarboxamide: Synthesis, characterization and single crystal X-ray studies of chalcogen (Se/Te) derivatives of N,N,N′,N′-tetraisopropylpyridine-2, 6-dicarboxamide

Article abstract of DOI:10.1016/j.tet.2014.05.066

The lithiation of N,N,N′,N′-tetraisopropylpyridine-2,6- dicarboxamide (1) and its application in the synthesis of chalcogen (Se/Te) derivatives was investigated. It was found that the selectivity of the reaction changed with the change in the amount of n-BuLi used. The lithiation of 1 with 6.1 equiv of n-BuLi followed by subsequent reactions with selenium/tellurium and iodomethane exclusively afforded the monosubstituted chalcogen derivative (2a/2b) in excellent yield. However, the use of 2.1 or 4.2 equiv of n-BuLi gave two additional products along with 2a/2b. One of the isolated products corresponded to the double lithiation of 1 and the other to the ortho lithiation followed by nucleophilic addition of n-BuLi to the one of the two carbonyl moieties. The prepared compounds have been characterized by single crystal X-ray crystallography, NMR (¹H, ¹³C, ⁷⁷Se and ¹²⁵Te), IR, UV-Visible and Mass spectroscopy. Crystal structure of N,N,N′,N′-tetraisopropyl-3,5-bis(methyltelluryl)pyridine-2, 6-dicarboxamide (3b) reveals a strong intramolecular ?O?Te secondary and intermolecular Te?π pyridyl interactions.

Full text of DOI:10.1016/j.tet.2014.05.066

Tetrahedron xxx (2014) 1e8
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Lithiation of N,N,N0,N0-tetraisopropylpyridine-2,6-dicarboxamide:
synthesis, characterization and single crystal X-ray studies of
chalcogen (Se/Te) derivatives of N,N,N0,N0-tetraisopropylpyridine-
2,6-dicarboxamide
,
a
a
a
b
Jaspreet S. Dhau a , Rupy Dhir , Avtar Singh , Amritpal Singh , Paula Brandao ,
Vítor Felix
*
~
c
ꢀ
a Department of Chemistry, Punjabi University, Patiala 147002, India
b Departamento de Química, CICECO, Universidade de Aveiro, Aveiro 3810-193, Portugal
c
~
ꢀ
^
ꢀ
Departamento de Química, CICECO, and Secc¸ ao Autonoma de Ciencias da Saude, Universidade de Aveiro, Aveiro 3810-193, Portugal
a r t i c l e i n f o
a b s t r a c t
The lithiation of N,N,N0,N0-tetraisopropylpyridine-2,6-dicarboxamide (1) and its application in the syn-
thesis of chalcogen (Se/Te) derivatives was investigated. It was found that the selectivity of the reaction
changed with the change in the amount of n-BuLi used. The lithiation of 1 with 6.1 equiv of n-BuLi
followed by subsequent reactions with selenium/tellurium and iodomethane exclusively afforded the
monosubstituted chalcogen derivative (2a/2b) in excellent yield. However, the use of 2.1 or 4.2 equiv of
n-BuLi gave two additional products along with 2a/2b. One of the isolated products corresponded to the
double lithiation of 1 and the other to the ortho lithiation followed by nucleophilic addition of n-BuLi to
the one of the two carbonyl moieties. The prepared compounds have been characterized by single crystal
X-ray crystallography, NMR (1H, 13C, 77Se and 125Te), IR, UVeVisible and Mass spectroscopy. Crystal
structure of N,N,N0,N0-tetraisopropyl-3,5-bis(methyltelluryl)pyridine-2,6-dicarboxamide (3b) reveals
Article history:
Received 25 February 2014
Received in revised form 18 May 2014
Accepted 20 May 2014
Available online xxx
Keywords:
Organochalcogen
Selenium
Tellurium
Te/
p interactions
a strong intramolecular CꢀO/Te secondary and intermolecular Te/
p pyridyl interactions.
Lithiation
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
an attempt to investigate the lithiation of 1 with the emphasis on
the synthesis of the corresponding chalcogen derivatives. The
crystal structures of some of the representative compounds have
been determined by single crystal X-ray diffraction analysis in order
to elucidate the Se/Te/heteroatom secondary interactions in these
molecules.
Organoselenium and -tellurium compounds exhibiting Se/
Te/heteroatom (N/O/halogen atoms) secondary interaction have
shown immense potential as biological active agents,1,2 chiral re-
agents for asymmetric synthesis3 and precursor to semiconducting
materials.4e6 The presence of these secondary interactions often
lead to the isolation of many hypervalent organochalcogen7,8 and
trichalcogen compounds.9 Recently, we have reported the synthesis
of
internally
chelated
chalcogen
derivatives
of
2-
pyridylcarboxamides through the lithiation of N,N-diisopropylpyr-
idine-2-carboxamide.10 While the lithiation of phenyl-11,12 and
pyridylcarboxamides12e14 has been well investigated, the corre-
sponding chemistry of dicarboxamides is unexplored. To the best of
our knowledge, there is no report on the lithiation of N,N,N0,N0-
tetraisopropylpyridine-2,6-dicarboxamide (1). The present work is
2. Results and discussion
2.1. Synthesis of chalcogen derivatives of 1
The reaction of 1 with 2.1 equiv of n-BuLi in dry THF followed by
treatment with selenium gave the corresponding selenolate anion,
which on quenching with iodomethane afforded 2a in 64% yield.
Two more products, 3a and 4a were also obtained from the reaction
in a 5% and 10% yield, respectively (Scheme 1). The use of tellurium
* Corresponding author. Present address: University of South Florida, De-
partment of Electrical Engineering, Tampa, FL 33620, USA. Tel.: þ1 813 974 4787;
fax: þ1 813 974 2050; e-mail addresses: jassiv02@yahoo.co.in, jaspreetdhau@usf.
edu (J.S. Dhau).
0040-4020/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2014.05.066
Please cite this article in press as: Dhau, J. S.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.05.066

2
J.S. Dhau et al. / Tetrahedron xxx (2014) 1e8
ECH3
(i-Pr)2N
N(i-Pr)2
N
ECH3
i) n-BuLi (2.1-4.1 eq.)
-78oC, 2hr
O
O
2a/2b
Bu
N(i-Pr)2
(i-Pr)2N
N(i-Pr)2
N
N
ii) E, -78oC to rt
O
O
O
O
iii) CH3I, -78oC, iv) H2O
4a/4b
H3CE
ECH3
1
(i-Pr)2N
N(i-Pr)2
N
O
O
a:- E = Se; b:- E = Te
3a/3b
Scheme 1. Lithiation of 1 with 2.1 equiv of n-BuLi.
instead of selenium in the later reaction afforded 2b, 3b, and 4b in
47%, 6% and 20% yield, respectively (Scheme 1). The compound 3a/
3b results from the double lithiation of 1 at the positions that are
ortho to the two carboxamides moieties. The formation of 4a and 4b
suggests ortho lithiation followed by nucleophilic addition of n-BuLi
to the one of the two carbonyl moieties of 1, which is surprising as
N,N-diisopropylcarboxamides are known to resist the nucleophilic
addition of n-BuLi.15,16
The reactions involving electrophiles other than iodomethane
proceeded without the formation of any by-product. The treatment
of the selenolate anion, with iodoethane, bromopropane, iodobu-
tane and (chloromethyl)benzene afforded 5a, 6a, 7a, and 8a, re-
spectively in moderate (54e58%) yields (Scheme 2, Table 1, entries
1e4). In another variation, the selenolate anion was directly hy-
drolyzed and subjected to aerial oxidation to afford the corre-
sponding diselenide, 9a, in 48% yield (Scheme 2). Since the
products corresponding to 3a and 4a were not isolated from the
later reactions, it can be inferred that the nature of the electrophile
plays a detrimental role in the formation of the by-products. This
was confirmed when we investigated the reaction with iodine as
the electrophile. The treatment of 1 with 2.1 equiv of n-BuLi and
subsequent trapping with iodine gave 10 and 11 in 52% and 20%
yield, respectively (Scheme 2).
Next, the role of the amount of n-BuLi on the selectivity of the
reactions depicted in Scheme 1 was examined. Our thought was
that an increase in the amount of n-BuLi would lead to increase in
the proportion of 3a/3b and 4a/4b. This to some extent was the case
when 4.1 equiv of n-BuLi was used. There was 10% increase in the
yield of 4a and a corresponding decrease in the yield of 2a (Table 1,
entry 6). This suggested nucleophilic addition of n-BuLi on the
carbonyl moiety of 2a. However, the reaction of 1 with 6.1 equiv of
n-BuLi gave result that was contrary to the expectation. 2a/2b was
the sole product obtained and there was no indication of the for-
mation of 3a/3b or 4a/4b (Table 1, entries 7 and 8). Similarly, the
monosubstituted product, 10, was the only product obtained when
iodine was used as the electrophile (Table 1, entry 9). In case of the
reactions where no by-products were formed (Table 1, entries 3 and
5), a substantial improvement in the yield of the product was no-
ticed (Table 1, entries 10 and 11).
In light of the above results, it appears that a pure organolithium
species (RLi)x exists in equilibrium with a lithium hetero-aggregate,
[(RLi)x (n-BuLi)6ꢁx], (Scheme 3). At a lower n-BuLi concentration,
Scheme 2. Synthesis of selenium and iodo derivative of 1.
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J.S. Dhau et al. / Tetrahedron xxx (2014) 1e8
3
Table 1
Lithiation of 1 with n-BuLi or LDA
Entry
Base (equiv)
Electrophile
Product (yield)
1.
2.
3.
4.
5.
6.
7.
8.
n-BuLi (2.1)
n-BuLi (2.1)
n-BuLi (2.1)
n-BuLi (2.1)
n-BuLi (2.1)
n-BuLi (4.1)
n-BuLi (6.1)
n-BuLi (6.1)
n-BuLi (6.1)
n-BuLi (6.1)
n-BuLi (6.1)
LDA (2.1)
SeþC2H5I
5a (58%)
6a (58%)
7a (58%)
8a (54%)
9a (48%)
2a (54%), 3a (5%), 4a (25%)
2a (90%)
2b (77%)
10 (67%)
7a (74%)
9a (62%)
2a (86%)
2a (88%)
Seþn-C3H9Br
Seþn-C4H11
I
SeþPhCH2Cl
Se and aerial oxidation
SeþCH3I
SeþCH3I
TeþCH3I
9
I2
10.
11.
12.
13.
14.
Seþn-C4H11
I
Se and aerial oxidation
SeþCH3I
LDA (4.1)
LDA (4.1)
SeþCH3I
TeþCH3I
2b (75%)
Fig. 1. COSY NMR spectrum of 4b.
corresponding to eCH(CH3)2 protons) represents long range cou-
pling between these hydrogen nuclei. This suggests that eTeCH3 is
ortho to the carboxamide moiety rather to the keto group. TheꢁIR1 CꢀO
stretching band in 2a, 3a and 4a (1632, 1634 and 1628 cm , re-
spectively) is very close to the corresponding band in 1 (1629 cmꢁ1).
Scheme 3. Formation of lithium aggregate of 1.
the equilibrium lies more towards the left side that makes n-BuLi
available for the nucleophilic addition reaction. At a higher n-BuLi
concentration (6.1 equiv), the equilibrium shifts towards the ther-
modynamically more stable lithium hetero-aggregate so that n-
BuLi is not available for the addition reaction. This partly explains
the non-isolation of the bimetallated species in the later reactions.
The product yield of w50% in the reactions involving 2.1 equiv of n-
BuLi (Table 1, entries 1e5) also indicates towards the formation of
lithium aggregate in the reaction mixture. The formation of lithium
hetero-aggregates and its influence on the selectivity of the re-
action has been reported by other research groups also.17,18
We next investigated the reaction of 1 with lithium diisopro-
pylamide (LDA), which is a hindered and non-nucleophilic base.
The reaction of 1 with 2.1 equiv of LDA followed by selenium in-
sertion and trapping with iodomethane exclusively gave 2a in ex-
cellent yield (Scheme 4, Table 1, entry 12). The effect of the amount
of LDA on the selectivity of the reaction was examined in this case
also. Interestingly, there was no indication of any bimetallated
species when the amount of LDA was increased from 2.1 to 4.1 equiv
(Table 1, entries 13 and 14).
Conversely, this band appeared at a lower frequency (w1617 cmꢁ1
)
in the corresponding tellurium derivatives (2b, 3b, and 4b). The CꢀO
stretching band in the selenium derivatives, 5ae9a, is also observed
at lower frequency than 1. All these observations are indicative of
the absence of CꢀO/Se interaction in 2ae4a and the presence of
CꢀO/Te interaction in the corresponding tellurium derivatives. The
later inference has been validated by X-ray structure of 2a, 3b, and
4b. A direct correlation between the 125Te NMR chemical shifts and
the strength of CꢀO/Te intramolecular interactions has also been
observed. The 125Te NMR signal in 2b and 3b appears at
327.2 ppm, respectively. The shortest CꢀO/Te intramolecular dis-
d 315.0 and
ꢁ
ꢁ
tance in 3b is found to be 3.1992 A, whereas it is 2.825 A in 4b.
The UVeVisible spectra of 2a and 5ae8a show three intense
absorption bands (one * and two n/
expectation, the n1/
* transition band in 2a, 5a and 6a is more
intense than the /p* transition band. Selenium atom is re-
p/p
p*). Contrary to the
p
p
sponsible for this hyperchromic effect as the corresponding band in
the tellurium derivatives and starting material is less intense than
the
shows only two absorption bands. While there is no change in the
position of * transition band relative to 2a/2b, the n/ * band
p/p* transition band. Interestingly, the compound 3a and 3b
p/p
p
shows large bathochromic shift, and is sensitive to the nature of the
chalcogen atom (Fig. 2). The later band in 4b is broader and 37 nm
to the red of the corresponding selenium derivative.
Scheme 4. Treatment of 1 with 6.1 equiv of n-BuLi or 2.1/4.1 equiv of LDA.
2.3. Solid state structural features of 2a, 3b, and 4b
2.2. Spectroscopic studies
The single crystal X-ray studies were carried out in order to
determine structural features of 2a, 3b and 4b. The crystals were
grown in a solution of hexane and ethyl acetate. Fig. 3a depicts the
molecular structure of 2a and Table 2 shows its selected bond
lengths and angles. The two carbonyls of the amide groups adopt
a syn-spatial disposition relatively to the pyridine ring with the
ortho and para amide units intercepting the pyridine ring at
49.47(7)ꢂ and 86.22 (8)ꢂ, respectively. The C(25)eSeeC(1)eC(2)
torsion angle of 173.1ꢂ(1) indicates that the eSeCH3 is planar to the
The 1H NMR spectra of 2a, 2b, 4a, 4b, 5ae9a,10, and 11 show two
doublets in the aromatic region. On the other hand, the 1H NMR
spectra of 3a and 3b showed only one singlet in the aromatic region
indicating double lithiation of the pyridine ring. The [1He1H] COSY
NMR technique was used to determine the position of eTeCH3 in 4b
as 1H NMR data was inconclusive. A horizontal line (Fig. 1) from the
spot at
that meets the two low intensity off-diagonal spots (labeled B and C,
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d 2.28 ppm (labeled A, corresponding to eTeCH3 protons)
2
ꢁ
pyridine ring. The C(sp )eSe bond length (1.908(1) A) in 2a is much

4
J.S. Dhau et al. / Tetrahedron xxx (2014) 1e8
37.5(2)ꢂ, which is mainly due to the presence of the sterically de-
manding ortho carboxamide group.
The crystal structure of 4b is built from an asymmetric unit
composed of two independent molecules (A and B) shown in
Fig. 4a. These molecules have identical structures as indicated by
the selected bond distances and angles listed in Table 3. Indeed, the
rms between two molecules, excluding the hydrogen atoms, is only
ꢁ
0.142 A. As observed for 3b, the two carbonyls of the amide groups
adopt an anti-configuration in each molecule relatively to the cor-
responding pyridine ring. These two molecules exhibit similar
TeeC bond lengths and CeTeeC and CeCeTe angles, which are
consistent with a ‘V’ shaped geometry around each tellurium atom.
Interestingly, the two eTeCH3 substituents in both the independent
molecules are almost coplanar with the pyridine ring while it is out
of the plane of the pyridine ring in 3b. In the crystal structure of 4b,
the molecules A and B adopt an almost parallel disposition estab-
lishing two independent Te/p pyridyl interactions with distances
ꢁ
of 3.852 and 3.662 A between Te and the centroid of the pyridine
rings (see Fig. 4b). In addition, the structure of 4b also exhibits
Fig. 2. UV-Visible spectra of 4a and 4b.
Fig. 3. ORTEP diagram of 2a (left) and 3b (right) with the thermal ellipsoids drawn at the 50% probability level and labeling scheme used for selected atoms.
Table 2
intramolecular secondary interactions between the Te and O atoms
ꢂ
ꢁ
Selected bond lengths (A) and bond angles ( ) of 2a
of the carboxamide groups. The Te(2A)/O(17A) distance is
ꢁ
ꢁ
2.825(2) A, whereas Te(1A)/O(8A) distance is 3.164(2) A. The
SeeC(1)
C(7)eO(8)
C(16)eO(17)
C(1)eSeeC(25)
1.908(1)
1.231(2)
1.230(2)
99.99(7)
SeeC(25)
C(7)eN(9)
C(16)eN(18)
SeeC(1)eC(2)
1.934(2)
1.344(2)
1.353(2)
118.0(1)
ꢁ
Te/O distance of 2.825(2) A is one of the smallest distances known
among the organotellurium compounds.25
3. Conclusions
smaller than that found in substituted bis(2-pyridyl) diselenides
19e23
ꢁ
In conclusion, we have provided an efficient methodology for the
lithiation of N,N,N0,N0-tetraisopropylpyridine-2,6-dicarboxamide,
which is useful for the synthesis of the corresponding ortho
substituted chalcogen derivatives. In addition, we have demon-
strated change in the selectivity of the reaction with the change
in the amount of n-BuLi used. Strong intramolecular CꢀO/Te sec-
(1.920e1.934
A)
and
bis(methylselenenyl)pyridines
21,22
In contrast, the C(sp3)eSe bond length
ꢁ
(1.914e1.929 A).
21,22
ꢁ
(1.935(2) A) is similar to that in bis(methylselenenyl)pyridines.
The shortest Se/O distance of 3.439(1) A, slightly more than the
sum of oxygen and selenium atoms van der Waals radii (3.42 A),
ꢁ
24
ꢁ
indicates the absence of a Se/O (carbonyl) secondary interaction.
The asymmetric unit of 3b presented in Fig. 3b shows that the
two carbonyl groups are positioned above and below the pyridine
ring with a torsion angle between them of ꢁ139.2(3)ꢂ, which is
consistent with the anti-configuration. The amide groups ortho and
para to the eTeCH3 substituent are rotated relatively to the pyridine
ring by a dihedral angle of 52.11(1)ꢂ and 50.47(3)ꢂ, respectively. The
O atom belonging to the ortho carboxamides moiety points towards
the Te atom, and is responsible for a very strong Te/O secondary
ondary and intermolecular Te/
p pyridyl interactions has been
identified in N,N,N0,N0-tetraisopropyl-3,5-bis(methyltelluryl)pyri-
dine-2,6-dicarboxamide.
4. Experimental section
4.1. General
ꢁ
interaction at an intramolecular distance of 3.199(2) A. This dis-
All the reactions were carried out under nitrogen atmosphere.
Solvents were dried by standard procedures and were freshly dis-
tilled prior to use.26 The 1H NMR and 13C NMR spectra were ob-
tained at Bruker 400 MHz spectrophotometer in CDCl3. The 1H
tance is significantly shorter than the sum of their van der Waals
radii of 3.62 A.24 The eTeCH3 unit is oriented out of the plane of the
ꢁ
pyridine ring with the C(6)eC(1)eTeeC(25) torsion angle of
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J.S. Dhau et al. / Tetrahedron xxx (2014) 1e8
5
Fig. 4. Different structural features of the Crystal structure of 4b: ORTEP diagram of asymmetric unit of 4b showing the two independent crystallographic molecules with thermal
ellipsoids drawn at the 60% probability level (left); molecular diagram showing the Te/
p and Te/O intermolecular interactions drawn as red and blue dashed lines (right),
respectively.
Table 3
ꢂ
ꢁ
Selected bond lengths (A) and bond angles ( ) of 3b and 4b
4.3. Preparation of (methylselenenyl) derivatives of 1
Compound
3b
4b
A
Treatment of 1-Se with iodomethane (0.894 g, 0.38 mL,
6.3 mmol) followed by hydrolysis and purification by column
chromatography (silica gel 100e120 mesh, hexane/EtOAc 10:1)
yielded three products, 2a (0.83 g, 64%), 3a (0.05 g, 5%) and 4a
(0.11 g, 10%). However, the use of 6.1 equiv of n-BuLi (7.32 mL,
18.3 mmol, 2.5 N), 2.1 or 4.1 equiv of LDA (6.3 or 12.3 mmol) in the
later reaction exclusively gave 2a in 90% (1.53 g), 86% (1.09 g) and
88% (1.13 g) yield, respectively.
B
Te(1)eC(1)
Te(1)eC(25)
Te(2)eC(5)
Te(2)eC(26)
C(7)eO(8)
C(16)eO(17)
C(1)eTe(1)eC(25)
C(5)eTe(2)eC(26)
Te(1)eC(1)eC(2)
Te(1)eC(1)eC(6)
Te(2)eC(4)eC(5)
Te(2)eC(5)eC(6)
2.116(2)
2.133(3)
d
2.115(3)
2.142(3)
2.110(2)
2.134(3)
1.233(3)
1.238(3)
95.2(1)
2.114(3)
2.133 (3)
2.102(2)
2.135(3)
1.235(3)
1.235(3)
95.3(1)
d
1.229(3)
1.227(3)
93.8(1)
d
95.4(1)
94.6(1)
122.3(2)
121.2(2)
d
120.0(2)
122.1(2)
120.1(2)
122.1(2)
121.1(2)
121.6(2)
122.1(2)
120.8(2)
4.3.1. N,N,N0,N0-Tetraisopropyl-3-(methylselenenyl)pyridine-2,6-
dicarboxamide (2a). Brown crystalline solid; Mp 120e121 ꢂC;
[Found: C, 56.49; H, 7.96; N, 9.91. C20H33N3O2Se requires C, 56.32; H,
d
7.79; N, 9.85%]; Rf (30% EtOAc/hexane) 0.65; 1H NMR (400 MHz,
NMR and 13C NMR chemical shifts were cited with respect to tet-
ramethylsilane as an internal standard. The 77Se and 125Te NMR
spectra were recorded in CDCl3 using 4-dimethylamino-2,6-
3
CDCl3):
d
¼7.73e7.71 (d, 1H, J¼8.0 Hz, CHAr(4)), 7.43e7.41 (d, 1H, d,
3J¼8.0 Hz, CHAr(3)), 4.08e4.03 (m, 1H, CH), 3.58e3.51 (m, 1H, CH),
3.49e3.42(m, 2H, CH), 2.25(s, 3H, SeCH3),1.50e1.48 (d, 6H, 3J¼6.8 Hz,
CH3), 1.45e1.44 (d, 6H, 3J¼6.8 Hz, CH3), 1.11e1.10 (d, 6H, 3J¼6.6 Hz,
CH3), 1.08e1.07 (d, 6H, 3J¼6.6 Hz, CH3) ppm; 13C NMR (100 MHz,
bis(methylselenenyl)pyridine
and
4-dimethylamino-2,6-
bis(methyltelluryl)pyridine, respectively, as external standards on
Bruker Avance 400 MHz spectrometer. The ESI mass spectra were
taken on Water Q-TOF Micro spectrometer. The EI mass spectra
were taken by using GC-Mass Spectrometer [GCeMS QP-2010 plus]
CDCl3):
d
¼167.8,167.4,153.9,152.2,138.7,128.2,123.4, 50.9, 50.9, 46.2,
46.0, 20.7, 20.6, 20.4, 20.3, 7.0 ppm; 77Se NMR (400 MHz, CDCl3):
d
¼188.3 ppm; IR (KBr) ¼3061, 2965, 2873, 1632, 1552, 1458, 1443,
n
with Rtx-1MS (30mꢃ0.25 mm IDꢃ0.25
mm) capillary column. The
1413, 1206, 1039 cmꢁ1; UVevis (CHCl3): lmax (log ε)¼306 (3.9), 286
UV-Visible spectra were taken in chloroform on Shimadzu Phar-
maSpec UV-1700 spectrophotometer. Microanalysis was carried
out on Vario MICRO Elemantar analyzer at Department of Chem-
istry, Punjabi University, Patiala.
(4.0), 253 (3.9) nm; MS (ESI) m/z¼450 [MþNa (80Se)]þ.
4.3.2. N,N,N0,N0-Tetraisopropyl-3,5-bis(methylselenenyl)pyridine-2,6-
dicarboxamide (3a). Light yellow crystalline solid, Mp 162e164 ꢂC;
[Found: C, 48.68; H, 6.84; N, 8.11. C21H35N3O2Se2 requires C, 48.55;
H, 6.79; N, 8.08%]; Rf (30% EtOAc/hexane) 0.8; 1H NMR (400 MHz,
4.2. General procedure
CDCl3):
d
¼7.75 (s, 1H, CHAr(4)), 3.77e3.73 (m, 2H, CH), 3.54e3.50
n-BuLi (2.52 mL, 6.3 mmol, 2.5 N) was added to a solution of 1
(0.999 g, 3.0 mmol) in dry THF (30 mL) at ꢁ78 ꢂC. The reaction
mixture was stirred for 2 h at the same temperature and selenium
(0.497 g, 6.3 mmol) or tellurium (0.812 g, 6.3 mmol) powder was
added to it. The reaction mixture was slowly brought to room
temperature and stirred till most of the selenium/tellurium got
dissolved. The selenolate or tellurolate anion thus obtained was
labeled as 1-Se and 1-Te, respectively.
(m, 2H, CH), 2.32 (s, 6H, SeCH3), 1.55e1.54 (d, 12H, 3J¼6.8 Hz, CH3),
1.16e1.15 (d, 12H, 3J¼6.7 Hz, CH3) ppm; 13C NMR (100 MHz, CDCl3):
d
¼167.1, 151.9, 139.8, 128.0, 50.9, 46.1, 20.7, 20.3, 7.2 ppm; IR (KBr)
n
¼3060, 2959, 2871, 1630, 1540, 1446, 1405, 1205, 1038 cmꢁ1; MS
(ESI): m/z¼544 [MþNa (80Se)]þ
4.3.3. N,N-Diisopropyl-3-(methylselenenyl)-6-pentanoyl-
picolinamide (4a). Light yellow crystalline solid Mp 98e99 ꢂC;
Please cite this article in press as: Dhau, J. S.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.05.066

6
J.S. Dhau et al. / Tetrahedron xxx (2014) 1e8
[Found: C, 56.27; H, 7.30; N, 7.49. C18H28N2O2Se requires C, 56.38;
iodoethane (0.983 g, 0.51 mL, 6.3 mmol), and hydrolysis gave 5a as
a brown crystalline solid (0.78 g, 58%); Mp 40e42 ꢂC; [Found: C,
57.37; H, 7.96; N, 9.55. C21H35N3O2Se requires C, 57.26; H, 8.00; N,
9.53%]; Rf (30% EtOAc/hexane) 0.66; 1H NMR (400 MHz, CDCl3):
H, 7.36; N, 7.30%]; Rf (30% EtOAc/hexane) 0.90; 1H NMR (400 MHz,
CDCl3):
d
¼7.83e7.81 (d, 1H, 3J¼8.2 Hz, CHAr(4)), 7.74e7.72 (d, 1H, d,
3J¼8.2 Hz, CHAr(3)), 3.61e3.50 (m, 2H, CH), 3.08e3.05 (t, 2H, CH2),
2.28 (s, 3H, SeCH3), 1.62e1.61 (m, 2H, CH2), 1.54e1.53 (d, 6H,
3J¼6.8 Hz, CH3), 1.34e1.32 (m, 2H, CH2), 1.14e1.12 (d, 6H, 3J¼6.7 Hz,
CH3), 0.87e0.83 (t, 3H, CH3) ppm; 13C NMR (100 MHz, CDCl3):
d
¼7.86e7.84 (d, 1H, 3J¼8.1 Hz, CHAr(4)), 7.49e7.47 (d, 1H, d,
3J¼8.1 Hz, CHAr(3)), 4.016e4.13 (m, 1H, CH), 3.60e3.49 (m, 3H, CH),
2.98e2.93 (q, 2H, SeCH2), 1.57e1.55 (d, 6H, 3J¼6.8 Hz, CH3),
1.52e1.50 (d, 6H, 3J¼6.8 Hz, CH3), 1.45e1.40 (t, 3H, CH3), 1.19e1.17
(d, 6H, 3J¼6.6 Hz, CH3), 1.15e1.13 (d, 6H, 3J¼6.6 Hz, CH3) ppm; 13C
d
¼200.7, 166.1, 153.2, 148.3, 136.3, 132.7, 120.5 49.8, 45.2, 36.2, 25.2,
21.4, 19.7, 19.3, 12.9, 5.6 ppm; IR (KBr)
n
¼3060, 2960, 2871, 1701,
1628, 1551,1464,1411,1207 cmꢁ1; UVevis (CHCl3): lmax (log ε)¼327
(3.8), 250 (3.5) nm; MS (ESI) m/z¼385 [Mþ1(80Se)]þ.
NMR (100 MHz, CDCl3):
123.2, 51.0, 50.9, 46.2, 45.9, 20.9, 20.7, 20.5, 20.4, 20.2, 15.0 ppm; IR
d
¼167.8, 167.5, 155.3, 152.7, 140.5, 126.1,
(KBr)
n
¼3057, 2963, 2867, 1621, 1559, 1461, 1445, 1417, 1210,
4.4. Preparation of (methyltelluryl) derivatives of 1
1038 cmꢁ1; UVevis (CHCl3): lmax (log ε)¼311 (4.0), 287 (4.1), 253
(4.0) nm; MS (ESI) m/z¼464 [MþNa (80Se)]þ.
Treatment of 1-Te with 6.3 mmol of iodomethane (0.894 g,
0.38 mL) yielded three different products, 0.67 g (47%) 2b, 0.11 g
(6%) 3b and 0.26 g (20%) 4b. However, the use of 6.1 equiv of n-BuLi
(7.56 mL, 18.9 mmol, 2.5 N) or 4.1 equiv of LDA (12.3 mmol) ex-
clusively gave 2b in 77% (1.10 g) and 75% (1.06 g) yield, respectively.
4.6. N,N,N0,N0-Tetraisopropyl-3-(propylselenenyl)pyridine-2,6-
dicarboxamide (6a)
The use of bromopropane (0.775 g, 0.57 mL, 6.3 mmol) instead
of iodomethane in the above reaction gave 6a as a yellow crystalline
solid (0.79 g, 58%). Mp 104e105 ꢂC; [Found: C, 58.26; H, 8.23; N,
9.23. C22H37N3O2Se requires C, 58.13; H, 8.20; N, 9.24%]; Rf (30%
4.4.1. N,N,N0,N0-Tetraisopropyl-3-(methyltelluryl)pyridine-2,6-
dicarboxamide (2b). Yellow crystalline solid, Mp 135e137 ꢂC;
[Found: C, 56.63; H, 7.05; N, 8.80. C20H33N3O2Te requires C, 56.56;
H, 7.00; N, 8.84%]; Rf (30% EtOAc/hexane) 0.60; 1H NMR (400 MHz,
EtOAc/hexane) 0.67; 1H NMR (400 MHz, CDCl3):
d
¼7.79e7.77 (d,
1H, 3J¼8.1 Hz, CHAr(4)), 7.41e7.39 (d, 1H, d, 3J¼8.1 Hz, CHAr(3)),
4.10e4.07 (m, 1H, CH), 3.52e3.42 (m, 3H, CH), 2.87e2.83 (t, 2H,
SeCH2), 1.69e1.60(m, 2H, CH2), 1.50e1.48 (d, 6H, 3J¼6.8 Hz, CH3),
1.46e1.44 (d, 6H, 3J¼6.8 Hz, CH3), 1.12e1.10 (d, 6H, 3J¼6.6 Hz, CH3),
CDCl3):
d
¼7.86e7.84 (d, 1H, 3J¼8.0 Hz, CHAr(4)), 7.32e7.30 (d, 1H, d,
3J¼8.0 Hz, CHAr(3)), 3.91e3.83 (m, 2H, CH), 3.48e3.43 (m, 2H, CH),
1.99 (s, 3H, TeCH3), 1.48e1.46 (d, 6H, 3J¼6.8 Hz, CH3), 1.46e1.44 (d,
6H, 3J¼6.8 Hz, CH3), 1.11e1.09 (d, 6H, 3J¼6.4 Hz, CH3), 1.09e1.08 (d,
1.08e1.06 (d, 6H, 3J¼6.6 Hz, CH3), 0.95e0.91 (t, 3H, CH3) ppm; 13
C
6H, 3J¼6.4 Hz, CH3) ppm; 13C NMR (100 MHz, CDCl3):
d¼167.8,167.1,
NMR (100 MHz, CDCl3):
123.3, 51.0, 50.9, 46.2, 45.9, 29.5, 23.1, 20.7, 20.5, 20.4, 20.3,
d
¼167.8, 167.5, 155.3, 152.7, 140.6, 126.5,
154.4, 151.2, 141.9, 122.2, 112.3 49.9, 45.2, 45.1, 19.7, 19.6, 19.4, 19.3,
ꢁ17.1 ppm; 125Te NMR (400 MHz, CDCl3):
d¼315.0 ppm; IR (KBr)
14.4 ppm; IR (KBr)
n
¼2965, 2930, 2872,1624, 1457, 1441, 1205, 1150,
n
¼3061, 2971, 2871, 1616, 1556, 1460, 1417, 1208, 1035 cm-1; UVevis
1132, 1104, 1040, 1028 cmꢁ1; UVevis (CHCl3): lmax (log ε)¼312
(4.0), 286 (4.0), 252 (4.0) nm; MS (EI): m/z¼455 [M (80Se)]þ.
(CHCl3): lmax (log ε)¼332 (3.7), 291 (3.8), 252 (4.0) nm; MS (ESI) m/
z¼500 [MþNa (130Te)]þ.
4.7. 3-(Butylselenenyl)-N,N,N0,N0-tetraisopropylpyridine-2,6-
dicarboxamide (7a)
4.4.2. N,N,N0,N0-Tetraisopropyl-3,5-bis(methyltelluryl)pyridine-2,6-
dicarboxamide (3b). Yellow crystalline solid, Mp 158e159 ꢂC;
[Found: C, 40.83; H, 5.70; N, 6.83. C21H35N3O2Te2 requires C, 40.89; H,
5.72; N, 6.81%]; Rf (30% EtOAc/hexane) 0.75; 1H NMR (400 MHz,
Theuseof1 (0.999 g, 3.0 mmol), n-BuLi (7.32 mL,18.3 mmol, 2.5 N),
selenium (1.445 g, 18.3 mmol), iodobutane (3.477 g, 2.16 mL,
18.3 mmol), and hydrolysis gave7aas ayellowcrystalline solid (1.04 g,
74%). Mp 84e85 ꢂC; [Found: C, 59.09; H, 8.30; N, 8.99. C23H39N3O2Se
requires C, 58.95; H, 8.38; N, 8.96%]; Rf (30% EtOAc/hexane) 0.70; 1H
CDCl3):
d
¼7.98 (s, 1H, CHAr(4)), 4.00e3.97 (m, 2H, CH), 3.53e3.50 (m,
2H, CH), 2.06 (s, 6H, SeCH3), 1.54e1.52 (d, 12H, 3J¼6.8 Hz, CH3),
1.18e1.16 (d, 12H, 3J¼6.7 Hz, CH3) ppm; 13C NMR (100 MHz, CDCl3):
d
¼168.6, 153.0, 146.9, 114.1, 51.0, 46.3, 20.8, 20.4, ꢁ16.0 ppm; 125Te
NMR (400 MHz, CDCl3):
d
¼7.79e7.77 (d, 1H, 3J¼8.1 Hz, CHAr(4)),
NMR (400 MHz, CDCl3):
d¼327.2 ppm; IR (KBr)
n¼3058, 2964, 2870,
7.42e7.40 (d, 1H, d, 3J¼8.1 Hz, CHAr(3)), 4.10e4.07 (m, 1H, CH),
3.51e3.42 (m, 3H, CH), 2.89e2.85 (t, 2H, SeCH2), 1.63e1.56 (m, 2H,
1691,1617,1542,1446,1409,1208 cmꢁ1; UVevis (CHCl3): lmax (log ε)¼
321 (3.8), 295 (3.7), 253 (3.9) nm; MS (ESI) m/z¼644 [MþNa (130Te)]þ.
CH2), 1.50e1.48 (d, 6H, 3J¼6.8 Hz, CH3), 1.45e1.43 (d, 6H, J¼6.8 Hz,
3
CH3), 1.38e1.32 (m, 2H, CH2), 1.12e1.10 (d, 6H, 3J¼6.6 Hz, CH3),
4.4.3. N,N-Diisopropyl-3-(methyltelluryl)-6-pentanoylpicolinamide
(4b). Yellow crystalline solid Mp 92e94 ꢂC; [Found: C, 50.17; H,
6.60; N, 6.45. C18H28N2O2Te requires C, 50.04; H, 6.53; N, 6.48%]; Rf
1.08e1.06 (d, 6H, 3J¼6.6 Hz, CH3), 0.85e0.82 (t, 3H, CH3) ppm; 13C
NMR (100 MHz, CDCl3):
d¼167.8, 167.5, 155.2, 152.6, 140.4, 126.6,
123.3, 51.0, 50.9, 46.2, 45.9, 31.8, 27.1, 22.9, 20.7, 20.5, 20.4, 20.3,
(30% EtOAc/hexane) 0.87; 1H NMR (400 MHz, CDCl3):
d
¼7.92e7.90
13.5 ppm; IR (KBr)
n
¼2962, 2929, 2871, 1628, 1457, 1441, 1418, 1258,
(d, 1H, 3J¼8.1 Hz, CHAr(4)), 7.75e7.73 (d, 1H, d, 3J¼8.1 Hz, CHAr(3)),
4.04e4.01 (m, 1H, CH), 3.54e3.51 (m, 1H, CH), 3.07e3.04 (t, 2H,
CH2), 2.00 (s, 3H, TeCH3), 1.65e1.57 (m, 2H, CH2), 1.55e1.51 (d, 6H,
3J¼6.8 Hz, CH3), 1.35e1.27 (m, 2H, CH2), 1.19e1.17 (d, 6H, 3J¼6.6 Hz,
CH3), 0.88e0.87 (t, 3H, CH3) ppm; 13C NMR (100 MHz, CDCl3):
1207, 1153, 1134, 1105, 1036 cmꢁ1; UVevis (CH3OH): lmax (log ε)¼315
(3.8), 286 (3.9), 249 (3.9) nm; MS (EI): m/z¼469 [M (80Se)]þ.
4.8. 3-(Benzylselenenyl)-N,N,N0,N0-tetraisopropylpyridine-2,6-
dicarboxamide (8a)
d
¼201.8, 168.3, 157.8, 149.4, 142.3, 121.5, 120.6, 50.8, 46.5, 37.2, 26.1,
22.5, 20.9, 20.4, 13.9, ꢁ15.6 ppm; IR (KBr)
n
¼3058, 2964, 2870, 1691,
According to general procedure, the use of 1 (0.999 g, 3.0 mmol),
n-BuLi (2.52 mL, 6.3 mmol, 2.5 N), selenium (0.497 g, 6.3 mmol),
(chloromethyl)benzene (0.797 g, 0.72 mL, 6.3 mmol) and hydrolysis
gave 8a as a yellow crystalline solid (0.81 g, 54%). Mp 92e96 ꢂC;
[Found: C, 62.11; H, 7.47; N, 8.43. C26H37N3O2Se requires C, 62.13; H,
7.42; N, 8.36%]; Rf (30% EtOAc/hexane) 0.72; 1H NMR (400 MHz,
1617, 1542, 1446, 1409, 1208 cmꢁ1; UVevis (CHCl3): lmax (log ε)¼
364 (3.6), 253 (3.8) nm; MS (ESI) m/z¼457 [MþNa (130Te)]þ.
4.5. 3-(Ethylselenenyl)-N,N,N0,N0-tetraisopropylpyridine-2,6-
dicarboxamide (5a)
CDCl3):
d
¼7.73e7.71 (d, 1H, 3J¼8.0 Hz, Ar), 7.38e7.36 (d, 1H, d,
According to general procedure, the use of 1 (0.999 g, 3.0 mmol),
n-BuLi (2.52 mL, 6.3 mmol, 2.5 N), selenium (0.497 g, 6.3 mmol),
3J¼8.0 Hz, Ar), 7.27e7.17 (5H, m, Ar), 4.09e4.06 (m, 1H, CH), 4.18 (s,
2H, SeCH2), 3.54e3.48 (m, 3H, CH), 1.58e1.56 (d, 6H, 3J¼6.7 Hz,
Please cite this article in press as: Dhau, J. S.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.05.066

J.S. Dhau et al. / Tetrahedron xxx (2014) 1e8
7
CH3), 1.52e1.51 (d, 6H, 3J¼6.7 Hz, CH3), 1.19e1.17 (d, 6H, 3J¼6.6 Hz,
CH3), 1.11e1.09 (d, 6H, 3J¼6.6 Hz, CH3) ppm; 13C NMR (100 MHz,
150(2)
K
using graphite monochromatized Mo-K
a
radiation
ꢁ
(
l
¼0.71073 A). The data reduction of each compound was carried
CDCl3):
d¼167.7, 167.5, 156.5, 153.6, 142.6, 137.7, 129.8, 128.4, 127.0,
out using the SAINT-NT software package from Bruker AXS.27 The
raw intensities were corrected for absorption effects through the
multi-scan method with the SADABS.28 The structures were solved
by a combination of direct methods and subsequent difference
Fourier syntheses and refined by full matrix least squares on F2
using the SHELX-2013 suite.29 Anisotropic thermal parameters
were used for all non-hydrogen atoms. The hydrogen atoms were
inserted at geometrical positions and refined with isotropic pa-
rameters equivalent 1.2 times those of the atom to which they are
bounded. The molecular diagrams were drawn with the Olex230
and PyMOL.31 The crystal data and refinement details for the
three compounds are gathered in Table 4.
125.1, 122.9, 50.9, 46.2, 45.9, 32.0, 20.7, 20.5, 20.4, 20.3 ppm; 77Se
NMR (400 MHz, CDCl3):
d
¼338.2 ppm; IR (KBr)¼3058, 2973, 2872,
1637, 1556, 1464, 1420, 1209, 1029 cmꢁ1; UVevis (CH3OH): lmax
(log ε)¼309 (3.7), 288 (3.9) 249 (4.1) nm; MS (ESI): m/z¼503 [M
(
80Se)]þ.
4.9. Bis[N,N,N0,N0-tetraisopropylpyridine-2,6-dicarboxamide]-
3,30-diselenide (9a)
The use of 1 (0.999 g, 3.0 mmol), n-BuLi (7.32 mL, 18.3 mmol,
2.5 N), selenium (1.445 g, 18.3 mmol) gave the selenolate anion. The
selenolate anion on hydrolysis and aerial oxidation yielded 9a as
a yellow solid (0.78 g, 62%). Mp 120e121 ꢂC; [Found: C, 55.57; H,
7.31; N, 10.29. C38H60N6O4Se2 requires C, 55.46; H, 7.34; N, 10.21%];
Rf (30% EtOAc/hexane) 0.43; 1H NMR (400 MHz, CDCl3):
Table 4
Crystal data and relevant refinement details of 2a, 3b, and 4b
Compound
2a
3b
4b
d
¼8.12e8.10 (d, 1H, 3J¼8.0 Hz, CHAr(4)), 7.39e7.37 (d, 1H, d,
Empirical formula
Mw
C
20H33N3O2Se
C20H33N3O2Te
475.09
Orthorhombic
Pbca
C21H35N3O2Te2
616.72
Triclinic
p1
3J¼8.0 Hz, CHAr(3)), 4.04e3.97 (m, 1H, CH), 3.90e3.84 (m, 1H, CH),
3.62e3.48 (m, 2H, CH), 1.58e1.56 (d, 6H, 3J¼6.7 Hz, CH3), 1.52e1.50
(d, 6H, 3J¼6.7 Hz, CH3), 1.21e1.19 (d, 6H, 3J¼6.6 Hz, CH3), 1.16e1.14
426.45
Monoclinic
P21/n
Crystal system
Space group
ꢁ
a/[A]
7.7819(6)
12.5851(9)
23.247(2)
(90)
99.434(4)
(90)
23.2324(10)
10.1166(5)
12.6511(6)
(90)
(90)
(90)
7.7951(3)
14.9764(6)
22.4767(9)
77.662(1)
83.419(1)
86.647(1)
2544.93(2)
4
(d, 6H, 3J¼6.6 Hz, CH3) ppm; 13C NMR (100 MHz, CDCl3):
¼167.8,
d
ꢁ
b/[A]
167.4,152.7,151.5,139.9,128.4,123.9, 51.1, 51.0, 46.5, 46.2, 20.8, 20.6,
ꢁ
c/[A]
20.4, 20.3 ppm; 77Se NMR (400 MHz, CDCl3):
d
¼408.7 ppm; IR
a
/[ꢂ]
/[ꢂ]
(KBr)¼3057, 2970, 2873, 1618, 1561, 1446, 1417, 1209, 1039 cmꢁ1
;
b
g
/[ꢂ]
UVevis (CHCl3): lmax (log ε)¼308 (3.9), 278 (4.2), 260 (4.2) nm; MS
3
ꢁ
V [A ]
2245.9(3)
4
4595.8(7)
8
(ESI): m/z¼825 [Mþ1 (80Se)]þ.
Z
Dc [Mg mꢁ3
]
1.261
1.373
1.610
4.10. Preparation of iodo derivatives of 1
m
/[mmꢁ1
]
1.689
1.312
2.312
Reflections collected
Unique reflections,
[Rint
Final R indices
R1, wR2 [I>2 I]
25,420
5373 [0.0285]
23,731
5509 [0.0498]
46,002
13,566 [0.0220]
The use of 1 (0.999 g, 3.0 mmol), n-BuLi (2.52 mL, 6.3 mmol,
2.5 N) and iodine (0.80 g, 6.3 mmol) gave 10 (0.71 g, 52%) and 11
(0.25 g, 20%). However, the use of 6.1 equiv of n-BuLi (7.32 mL,
18.3 mmol, 2.5 N) in the later reaction gave 10 in 67% (0.92 g) yield.
]
s
0.0289, 0.0683
[4626]
0.0384, 0.1004
[4017]
0.0299,0.0610
[11,715]
R1, wR2 (all data)
0.0364, 0.1439
0.0553, 0.1087
0.0389, 0.0652
4.10.1. 3-Iodo-N,N,N0,N0-tetraisopropylpyridine-2,6-dicarboxamide
(10). Light yellow solid, Mp 136e138 ꢂC; [Found: C, 49.58; H, 6.57; N,
9.21. C19H30N3O2I requires C, 49.67; H, 6.58; N, 9.14%]; Rf (30% EtOAc/
Acknowledgements
hexane) 0.67; 1H NMR (400 MHz, CDCl3):
d¼8.12e8.10 (d, 1H,
We are thankful to the CSIR, New Delhi, India, for financial
support (Scheme No.: 01(2345)/09/EMR-II). We are also thankful to
Mr. Avtar Singh, CIL, Panjab University, Chandigarh, for NMR
spectra.
3J¼8.2 Hz, CHAr(4)), 7.23e7.21 (d, 1H, d, 3J¼8.0 Hz, CHAr(3)),
4.05e3.98 (m, 1H, CH), 3.50e3.36 (m, 3H, CH), 1.51e1.49 (d, 6H,
3J¼6.8 Hz, CH3), 1.45e1.43 (d, 6H, 3J¼6.8 Hz, CH3), 1.12e1.11 (d, 6H,
3J¼2.8 Hz, CH3), 1.10e1.09 (d, 6H, 3J¼2.8 Hz, CH3) ppm; 13C NMR
(100 MHz, CDCl3):
d
¼167.4, 167.1, 157.3, 154.7, 147.7, 124.0, 89.9, 51.1,
Supplementary data
51.0, 46.3, 46.0, 20.7, 20.6, 20.4, 20.1 ppm; IR (KBr)
n
¼2967, 2927,
2872, 1628, 1458, 1442, 1205, 1155, 1136, 1106, 1039 cmꢁ1;.UVevis
(CHCl3): lmax (log ε)¼285 (3.7), 250 (3.7) nm; MS (EI): m/z¼459 [M]þ.
Crystallographic data has been deposited with the Cambridge
Crystallographic Data Centre, with numbers CCDC 978863, 978864,
and 978865, forcompounds 2a, 3b, and 4b, respectively. Copies of this
information may be obtained free of charge from: The Director, CCDC,
12 Union Road, Cambridge, CB2 1EZ, UK (Fax: þ44(01223)336033,
e-mail: deposit@ccdc.cam.ac.uk, or http://www.ccdc.cam.ac.uk).
4.10.2. 3-Iodo-N,N-diisopropylcarboxamide-6-pentanoylpyridine
(11). White solid, Mp 90e92 ꢂC; [Found: C, 49.18; H, 6.11; N, 6.63.
C
17H25N2O2I requires C, 49.04; H, 6.05; N, 6.72%]; Rf (30% EtOAc/
hexane) 0.85; 1H NMR (400 MHz, CDCl3):
d
¼8.21e8.19 (d, 1H,
3J¼8.3 Hz, CHAr(4)), 7.62e7.60 (d, 1H, d, 3J¼8.2 Hz, CHAr(3)),
3.56e3.49 (m, 1H, CH), 3.08e3.04 (m, 1H, CH), 3.08e3.04 (t, 2H,
CH2), 1.64e1.56 (m, 2H, CH2), 1.54e1.52 (d, 6H, 3J¼7.8 Hz, CH3),
1.36e1.27 (m, 2H, CH2), 1.14e1.12 (d, 6H, 3J¼7.3 Hz, CH3), 0.88e0.83
References and notes
€
1. Tripathi, S. K.; Patel, U.; Roy, D.; Sunoj, R. B.; Singh, H. B.; Wolmershauser, G.;
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€
(t, 3H, CH3) ppm; 13C NMR (100 MHz, CDCl3):
d
¼201.5, 167.4, 158.3,
151.8, 147.9, 122.1, 94.7, 51.2, 46.2, 37.3, 26.1, 22.4, 20.6, 20.2,
13.9 ppm; UVevis (CHCl3): lmax (log ε)¼307 (3.0), 279 (3.5), 254
(3.7) nm; MS (EI): m/z¼416 [M]þ.
€
7. Chauhan, A. K. S.; Anamika; Kumar, A.; Srivastava, R. C.; Butcher, R. J.; Beck-
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4.11. Crystallography
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The single crystal X-ray data of compounds 2a, 3b and 4b were
€
collected on a Bruker SMART Apex II CCD-based diffractometer at
ganometallics 2004, 23, 4199.
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J.S. Dhau et al. / Tetrahedron xxx (2014) 1e8
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Please cite this article in press as: Dhau, J. S.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.05.066