Iron(III) Chloride Catalyzed Nucleophilic Substitution of Tertiary Propargylic Alcohols and Synthesis of Iodo-3H-Pyrazoles

Article abstract of DOI:10.1055/s-0036-1588362

A straightforward and concise method was developed for the efficient and rapid synthesis of iodo-3H-pyrazoles by the FeCl₃/I₂-mediated propargylic substitution of tertiary propargylic alcohols with p-toluenesulfonyl hydrazide and subsequent cyclization under mild conditions. The method constitutes a novel approach to the synthesis of various iodo-3H-pyrazoles with a wide substrate scope and in high yields.

Full text of DOI:10.1055/s-0036-1588362

SYNLETT
0
9
3
6
-
5
2
1
4
1
4
3
7
-
2
0
9
6
© Georg Thieme Verlag Stuttgart · New York
2016, 27, A–E
letter
A
X.-T. Liu et al.
Letter
Synlett
Iron(III) Chloride Catalyzed Nucleophilic Substitution of Tertiary
Propargylic Alcohols and Synthesis of Iodo-3H-Pyrazoles
Xiao-Tao Liu*a
Zong-Cang Dingb
Lu-Chuan Jub
Zhao-Ning Tangb
Feng Wub
TsNHNH2
I2 (3 equiv)
NaHCO3 (3 equiv)
N
N
NHNHTs
R1
R2
FeCl3 (10 mol%)
MeNO2, 25 °C
R1
R2
+
R3
OH
R1
R2
MeCN, 25 °C
R3
I
R3
11 examples, up to 95% yield
11 examples, up to 94% yield
Zhuang-Ping Zhan*b
a Huaian Wanbang Aromatic Chemicals Industry Co., Ltd.,
Huaian 223300, Jiangsu, P. R. of China
b Department of Chemistry, College of Chemistry and Chemical
Engineering, Xiamen University, Xiamen 361005, Fujian,
P. R. of China
xiaotao.liu@wxintl.com
zpzhan@xmu.edu.cn
Received: 26.09.2016
Accepted after revision: 06.11.2016
Published online: 18.11.2016
gylic alcohols with various nucleophiles to achieve carbon–
carbon and carbon–heteroatom bond formations have been
extensively studied.2 Nevertheless, compared with the wide
range of applications of amine nucleophiles in C–N bond
formation, the substitution of propargylic alcohols, particu-
larly tertiary propargylic alcohols, with hydrazines as nu-
cleophiles has rarely been reported,3 even though propar-
gylic hydrazide products have been converted into useful
compounds that contain one or two nitrogen atoms and
that exhibit various biological activities.4 The first conve-
nient method for the preparation of propargylic hydrazides
from tertiary propargylic alcohols through scandium-cata-
lyzed hydrazination in MeNO2–H2O was reported by Yoshi-
matsu and co-workers in 2012 (Scheme 1, a).5 However,
when tertiary propargylic alcohols were used as substrates,
R3 was limited to a PhS group, and the presence of
Bu4NHSO4 as an additive was required.
DOI: 10.1055/s-0036-1588362; Art ID: st-2016-w0640-l
Abstract A straightforward and concise method was developed for
the efficient and rapid synthesis of iodo-3H-pyrazoles by the FeCl3/I2-
mediated propargylic substitution of tertiary propargylic alcohols with
p-toluenesulfonyl hydrazide and subsequent cyclization under mild
conditions. The method constitutes a novel approach to the synthesis
of various iodo-3H-pyrazoles with a wide substrate scope and in high
yields.
Key words propargylic alcohols, tosyl hydrazide, iodopyrazoles, cy-
clization, iodination
Transition-metal-catalyzed cascade reactions of propar-
gylic alcohols have received considerable attention, be-
cause many complicated molecules can be directly con-
structed by these reactions from readily accessible starting
materials under mild conditions.1 Among such reactions,
Lewis acid catalyzed nucleophilic substitutions of propar-
Our group has made great efforts to synthesize hetero-
cycles by using propargylic alcohols as substrates,6 and we
have reported a novel FeCl3-catalyzed domino regioselec-
NHNHTs
Sc(OTf)3
R1
R2
CN
Bu
4NHSO4
FeCl3
R1
R2
(a)
MeNO2/H2O
R3
R3 = TMS
OH
R2
(c)
TsNHNH2
R1
+
R3
1
2
R1
R2
R1
NNHTs
R3
N
Y(OTf)3
, PhCl
1) FeCl3
FeCl3
MeNO2
NH
R2
MeCN, 80 °C
2) Cs2CO3 (2 equiv)
(b)
R3
NHNHTs
R2
(d)
R1
R2
N
N
I2, NaHCO3
MeCN, r.t.
R1
R3
R3
R3 = Aryl, alkyl
I
(e) This work
3
4
Scheme 1 Reactions of tertiary propargylic alcohols 1 with p-toluenesulfonyl hydrazide (2)
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–E

B
X.-T. Liu et al.
Letter
Synlett
tive propargylic substitution/aza-Meyer–Schuster rear-
rangement reaction for the synthesis of acrylonitriles from
trimethylsilyl-substituted tertiary propargylic alcohols and
p-toluenesulfonyl hydrazide (Scheme 1, c).7 We have also
developed a one-pot synthesis of pyrazoles from the same
starting materials through a four-step cascade sequence
(Scheme 1, d).8 More recently, Chen and co-workers report-
ed the Y(OTf)3-catalyzed stereoselective synthesis of α,β-
unsaturated hydrazones from tertiary propargylic alcohols
and p-toluenesulfonyl hydrazide (Scheme 1, b).9 As part of
our ongoing efforts to expand the synthetic utility of tertia-
ry propargylic hydrazides, we report a highly efficient
FeCl3-catalyzed substitution of tertiary propargylic alcohols
to give propargylic hydrazides, and the synthesis of iodo-
3H-pyrazoles (Scheme 1, e). 3H-Pyrazole derivatives are
used extensively in syntheses of cyclopropenes, carbene in-
termediates, and diazoalkenes; they can also undergo rear-
rangements, cycloadditions, or Diels–Alder reactions.10
However, approaches to this family of heterocycles usually
rely on the cycloaddition of diazo compounds, which al-
ways presents danger.11 To the best of our knowledge, there
are few reports on the preparation of iodo-3H-pyrazoles or
their derivatization.
sulted in an unsatisfactory yield of 3a (entry 3). To our de-
light, the reaction in MeNO2 gave a 95% yield of 3a at room
temperature (entry 4); raising the reaction temperature
gave lower yields (entries 5 and 6). A test with PhCl as the
solvent was unsuccessful (entry 7). In contrast, reducing
the amount of FeCl3 to 5 mol% led to a decrease in the yield
of 3a to 84% (entry 8). Therefore, the optimal conditions for
this reaction were determined to be MeNO2 as the solvent,
at room temperature, with FeCl3 (10 mol%) as the catalyst
for about six hours (entry 4).
We next optimized the I2-mediated synthesis of 4-iodo-
3,3-dimethyl-5-phenyl-4,5-dihydro-3H-pyrazole (4a) from
hydrazide 3a (Table 2). We were pleased to find that the
propargyl hydrazide 3a could be smoothly converted into
the pyrazole 4a by treatment with three equivalents of I2
and NaHCO3 in MeCN (Table 2, entry 1; 94% yield). Reducing
the amounts of catalysts or changing the solvent resulted in
unsatisfactory yields (entries 2–5). Therefore, the optimal
reaction conditions for the cyclization of propargyl hydra-
zides are three equivalents of I2 and NaHCO3 as catalyst and
base, respectively, with MeCN as the solvent at room tem-
perature in air (entry 1).
In our previous studies, we found that FeCl3 is an effi-
cient catalyst for propargylic substitution. To prepare prop-
argyl hydrazides with high efficiency, we screened various
solvents and temperatures (Table 1). Initially, the tertiary
propargylic alcohol 1a and p-toluenesulfonyl hydrazide (2)
were treated with FeCl3 (10 mol%) in dichloromethane at
room temperature; this gave the target product 3a in 89%
yield (Table 1, entry 1), whereas CH2Cl2 at reflux decreased
the yield to 50% (entry 2). Changing the solvent to MeCN re-
Table 2 Optimization of Reaction Conditions for the I2-Mediated Cy-
clization of Propargylic Hydrazide 3aa
NHNHTs
N
N
I2, NaHCO3
Ph
solvent, 25 °C, t
Ph
I
3a
4a
Entry
Solvent
I2 (equiv) NaHCO3 (equiv) Time (h) Yieldb (%)
1
2
3
4
5
MeCN
3.0
2.0
3.0
3.0
3.0
3.0
2.0
3.0
3.0
3.0
1
2
94
MeCN
89
Table 1 Optimization of Reaction Conditions for the Propargylic Sub-
MeNO2
MeOH
THF
4
88
stitutiona
24
24
N.R.c
N.R.
OH
NHNHTs
FeCl3 (10 mol%)
solvent
TsNHNH2
+
a Reaction conditions: 3a (0.5 mmol), solvent (5 mL), r.t., in air.
b Isolated yield based on 3a.
Ph
Ph
1a
2
3a
c No reaction.
Entry
Solvent
Temp (°C)
Time (h)
Yieldb (%)
Next, we evaluated the scope of the reaction under the
optimal conditions by placing various substituents at vari-
ous positions on the propargylic alcohol 1 (Scheme 2). A va-
riety of propargyl hydrazides 3 and the corresponding
iodo-3H-pyrazoles 4 were successfully obtained. Propargyl-
ic alcohols with a terminal aromatic group (R3 = Ph) reacted
better than did those with an alkyl group (3a versus 3c and
3d; 4a versus 4c and 4d). In addition, the presence of a long
chain at the propargyl position reduced the yield slightly
(3b and 4b; 72 and 90% yield, respectively). Substrates with
a phenyl and a methyl group in the propargyl position re-
acted smoothly to afford the desired products (3e–g, 78–
90% yield; 4e–g, 80–91% yield). Product 3h decomposed
over the course of column chromatography; however, 4h
1
2
3
4
5
6
7
8c
CH2Cl2
CH2Cl2
MeCN
MeNO2
MeNO2
MeNO2
PhCl
25
20
2
89
50
75
95
90
74
20
84
reflux
25
12
6
25
30
2
60
0.1
24
14
25
MeNO2
25
a Reaction conditions: 1a (0.5 mmol), 2 (0.75 mmol), solvent (5 mL), r.t., in
air.
b Isolated yield based on 1a.
c FeCl3 (5 mol%).
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–E

C
X.-T. Liu et al.
Letter
Synlett
N
N
I2 (3 equiv)
NaHCO3 (3 equiv)
OH
NHNHTs
R1
R2
R1
R2
FeCl3 (10 mol%)
MeNO2, 25 °C
R1
R2
R3
TsNHNH2
+
MeCN, 25 °C
R3
I
R3
1
2
3
4
NHNHTs
NHNHTs
NHNHTs
N
N
N
N
N
N
n-Bu
n-Bu
I
4b - 1 h, 90%
I
I
3a - 6 h, 95%
4a - 1 h, 94%
3b - 6 h, 72%
3c - 20 h, 60%
4c - 6 h, 50%
NHNHTs
N
N
NHNHTs
NHNHTs
N
N
N
N
Ph
Ph
4-ClC6H4
4-ClC6H4
I
I
I
4f - 7 h, 87%
3f - 0.7 h, 88%
3d - 0.8 h, 76%
4d - 1 h, 84%
3e - 1.5 h, 90%
4e - 4 h, 91%
NHNHTs
NHNHTs
4-FC6H4
NHNHTs
N
N
N
N
N
N
4-FC6H4
I
I
4i - 5 h, 0%
I
3h - 5 h, 0%a
4h , 54%b
3i - 3 h, 83%
4g - 3 h, 80%
3g - 0.5 h, 78%
NHNHTs
N
I
NHNHTs
Ph
N
N
N
n-Bu
Ph
n-Bu
I
3j - 0.7 h, 66%
3k - 0.5 h, 63%
4k - 2 h, 80%
4j - 1 h, 46%
Scheme 2 Synthesis of propargyl hydrazides 3 and the corresponding iodo-3H-pyrazoles 4. Reagents and conditions: 1 (0.5 mmol), 2 (0.75 mmol), FeCl3
(10 mol%), MeNO2 (5 mL), r.t., air, then 3 (0.5 mmol), I2 (1.5 mmol), NaHCO3 (1.5 mmol), MeCN (5 mL), air, 25 °C. a 3h decomposed over the course of
column chromatography. b 4h was synthesized in one pot by reacting 1h and 2 for 12 h; upon completion of the reaction, MeNO2 was removed in vacuo
and the crude residue was treated with iodine and NaHCO3 in MeCN.
was obtained in a moderate 54% yield by a one-pot synthe-
Ph
Ph
sis starting from 1h and 2. On replacing a cyclohexyl group
1.3 equiv
with a cyclopentyl group, we obtained 3i successfully in
Pd(PPh3)Cl2 (10 mol%), CuI (10 mol%)
N
N
Ph
83% yield, but this could not be converted into the iodo-3H-
pyrazole 4i. Interestingly, the present method was also
compatible with a large-ring propargyl alcohol as the sub-
strate, albeit with moderate efficiency (3j, 66% yield; 4j,
46% yield). Replacement of the phenyl group at R3 in 3e
with a butyl group was also tolerated (3k, 63% yield; 4k,
80% yield).
To demonstrate the synthetic utility of this method,
derivatization reactions of the iodo-3H-pyrazole 4a were
carried out (Scheme 3). Under classic conditions, the Sono-
gashira, Suzuki, and Heck reactions all proceeded smoothly
to give the corresponding products 5, 6, and 7 in 85, 90, and
91% yield, respectively.
Et3N, r.t., overnight
5 (85%)
N
N
PhB(OH)2 (1.3 equiv)
Pd(OAc)2 (5 mol%), Na2CO3 (1.0 equiv)
N
N
Ph
Ph
I
DMF/H2O (2:1), 100 °C, 4 h
4a (0.5 mmol)
Ph
6 (90%)
CO2Me
3.0 equiv
N
N
Pd(OAc)2 (10 mol%), (n-Bu)4NHSO4 (1.0 equiv)
Ph
Na2CO3 (2.5 equiv), DMF, 80 °C, overnight
CO2Me
Based on the experimental results presented above, the
reaction mechanism shown Scheme 4 is proposed. First, the
propargylic alcohol 1 reacts under iron catalysis to yield a
7 (91%)
Scheme 3 Derivatization reactions of the iodo-3H-pyrazole 4a
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–E

D
X.-T. Liu et al.
Letter
Synlett
propargylic cation. Next, propargylic substitution occurs re-
gioselectively by attack on the terminal nitrogen atom (–NH2)
of hydrazide 2 to give the substitution product 3. Coordina-
tion of the I+ catalyst with the alkyne activates the triple
bond of 3 to nucleophilic attack by the substituted nitrogen
atom of the hydrazide (–NHTs); subsequent elimination of
one molecule of 4-toluenesulfonic acid leads to the forma-
tion of the final product 4.
Wang, H.-s.; Liang, H.; Chen, Z.-f.; Qin, X.-h. Org. Lett. 2014, 16,
580. (f) Zhu, Y.; Yin, G.; Hong, D.; Lu, P.; Wang, Y. Org. Lett. 2011,
13, 1024. (g) Bauer, E. I. Synthesis 2012, 44, 1131. (h) Yin, G.;
Zhu, Y.; Zhang, L.; Lu, P.; Wang, Y. Org. Lett. 2011, 13, 940.
(i) Chatterjee, P.; Roy, S. J. Org. Chem. 2010, 75, 4413. (j) Yan, W.;
Wang, Q.; Chen, Y.; Petersen, J.; Shi, X. Org. Lett. 2010, 12, 3308.
(k) Fang, Z.; Liu, J.; Liu, Q.; Bi, X. Angew. Chem. Int. Ed. 2014, 53,
7209. (l) Yoshimatsu, M.; Watanabe, H.; Koketsu, E. Org. Lett.
2010, 12, 4192. (m) Fang, C.; Pang, Y.; Forsyth, C. Org. Lett. 2010,
12, 4528. (n) Sanz, R.; Miguel, D.; Martínez, A.; Álvarez-Gutiér-
rez, J. M.; Rodríguez, F. Org. Lett. 2007, 9, 727. (o) Zhan, Z.-p.;
Yang, W.-z.; Yang, R.-f.; Yu, J.-l.; Li, J.-p.; Liu, H.-j. Chem.
Commun. 2006, 3352.
H
N
H2N
Ts
R3
2
NHNHTs
(3) For selected examples of the use of secondary propargyl alco-
hols and hydrazines as nucleophiles, see: (a) Xu, S.-X.; Hao, L.;
Wang, T.; Ding, Z.-C.; Zhan, Z.-P. Org. Biomol. Chem. 2013, 11,
294. (b) Reddy, C.; Vijaykumar, J.; Grée, R. Synthesis 2013, 45,
830.
OH
R1
R2
R1
R2
Fe3+
R1
R2
R3
R3
H+
3
1
I+
(4) (a) Elguero, J.; Goya, P.; Jagerovic, N.; Silva, A. M. S. In Targets in
Heterocyclic Systems: Chemistry and Properties; Vol. 6; Attanasi,
O. A.; Spinelli, D., Eds.; RSC: Cambridge, 2002, 52. (b) Kiyokawa,
K.; Ito, Y.; Kakehi, R.; Ogawa, T.; Goto, Y.; Yoshimatsu, M. Eur. J.
Org. Chem. 2016, 4998.
Ts
NHNHTs
I
N
N
R1
R2
HN
N
R1
R2
R1
R2
R3
R3
H+
R3
– TsH
I
I
(5) Yoshimatsu, M.; Ohta, K.; Takahashi, N. Chem. Eur. J. 2012, 18,
15602.
4
Scheme 4 Plausible reaction mechanism
(6) (a) Wen, J.-J.; Zhu, Y.; Zhan, Z.-P. Asian J. Org. Chem. 2012, 1,
108. (b) Wang, T.; Chen, X.-l.; Chen, L.; Zhan, Z.-p. Org. Lett.
2011, 13, 3324. (c) Liu, X.-t.; Huang, L.; Zheng, F.-j.; Zhan, Z.-p.
Adv. Synth. Catal. 2008, 350, 2778. (d) Pan, Y.-m.; Zheng, F.-j.;
Lin, H.-x.; Zhan, Z.-p. J. Org. Chem. 2009, 74, 3148. (e) Gao, X.;
Pan, Y.-m.; Lin, M.; Chen, L.; Zhan, Z.-p. Org. Biomol. Chem. 2010,
8, 3259. (f) Hao, L.; Pan, Y.; Wang, T.; Lin, M.; Chen, L.; Zhan, Z.-
p. Adv. Synth. Catal. 2010, 352, 3215. (g) Zhan, Z.-p.; Yu, J.-l.; Liu,
H.-j.; Cui, Y.-y.; Yang, R.-f.; Yang, W-z.; Li, J.-p. J. Org. Chem. 2006,
71, 8298.
In conclusion, we have developed a highly efficient
method for the synthesis of propargyl hydrazides and their
corresponding iodo-3H-pyrazoles from tertiary propargylic
alcohols and p-toluenesulfonyl hydrazide.12 The reactions
are high-yielding with a broad substrate scope and proceed
under extremely mild conditions. The present method
complements conventional reactions for the preparation of
this family of compounds, and has potential applications in
medicinal chemistry.
(7) Hao, L.; Wu, F.; Ding, Z.-C.; Xu, S.-X.; Ma, Y.-L.; Chen, L.; Zhan, Z.-
p. Chem. Eur. J. 2012, 18, 6453.
(8) Hao, L.; Hong, J.-J.; Zhu, J.; Zhan, Z.-p. Chem. Eur. J. 2013, 19,
5715.
(9) Liu, W.; Wang, H.; Zhao, H.; Li, B.; Chen, S. Synlett 2015, 26,
2170.
Acknowledgment
(10) (a) Closs, G. L.; Boll, W. A. J. Am. Chem. Soc. 1963, 85, 3904.
(b) Hamdi, N.; Dixneuf, P. H.; Arfaoui, Y.; Haloui, E. J. Chem. Res.
2005, 289. (c) Hamdi, N.; Lachheb, J.; Msaddek, M. J. Soc. Alger.
Chim. 2007, 17, 37. (d) Anet, R.; Anet, F. A. L. J. Am. Chem. Soc.
1964, 86, 525. (e) Padwa, A.; Wannamaker, M. W.; Dyszlewski,
A. D. J. Org. Chem. 1987, 52, 4760. (f) Mataka, S.; Ohshima, T.;
Tashiro, M. J. Org. Chem. 1981, 46, 3960. (g) Jefferson, E. A.;
Warkentin, J. J. Org. Chem. 1994, 59, 455. (h) Franck-Neumann,
M. Angew. Chem. Int. Ed. 1967, 6, 79. (i) Rigby, J. H.; Kierkus, P. C.
J. Am. Chem. Soc. 1989, 111, 4125. (j) Merchant, R. R.; Allwood,
D. M.; Blakemore, D. C.; Ley, S. V. J. Org. Chem. 2014, 79, 8800.
(11) (a) Moritani, I.; Hosokawa, T.; Obata, N. J. Org. Chem. 1969, 34,
670. (b) Wenkert, E.; McPherson, C. A. J. Am. Chem. Soc. 1972, 94,
8084. (c) Pyron, R. S.; Jones, W. M. J. Org. Chem. 1967, 32, 4048.
(d) Zimmerman, H. E.; Hovey, M. C. J. Org. Chem. 1979, 44, 2331.
(12) N′-(1,1-Dimethyl-3-phenylprop-2-yn-1-yl)-4-toluenesul-
fonohydrazide (3a); Typical Procedure
We are grateful to the National Natural Science Foundation of China
(No. 21272190), and NFFTBS (No. J1310024).
Supporting Information
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0036-1588362.
S
u
p
p
ortioInfgrmoaitn
S
u
p
p
ortiInfogrmoaitn
References and Notes
(1) (a) Hao, L.; Zhan, Z.-P. Curr. Org. Chem. 2011, 15, 1625. (b) Ding,
C.-H.; Hou, X.-L. Chem. Rev. 2011, 111, 1914. (c) Ljungdahl, N.;
Kann, N. Angew. Chem. Int. Ed. 2009, 48, 642. (d) Detz, R.;
Hiemstra, H.; van Maarseveen, J. H. Eur. J. Org. Chem. 2009,
6263.
TsNHNH2 (2; 129.5mg, 0.75 mmol), propargylic alcohol 1a (80
mg, 0.5 mmol), and FeCl3 (8.1 mg, 0.05 mmol) were added to a
10 mL round-bottomed flask. MeNO2 (5 mL) was added, and the
mixture was stirred in air at r.t. until the reaction was complete
(TLC). The solvent was removed under vacuum, and the crude
(2) (a) Guillena, G.; Ramón, D.; Yus, M. Chem. Rev. 2010, 110, 1611.
(b) Debleds, O.; Gayon, E.; Ostaszuk, E.; Vrancken, E.; Campagne,
J.-M. Chem. Eur. J. 2010, 16, 12207. (c) Kabelka, G. W.; Yao, M.-L.
Curr. Org. Synth. 2008, 5, 28. (d) Bandini, M.; Tragni, M. Org.
Biomol. Chem. 2009, 7, 1501. (e) Wang, X.; Li, S.-y.; Pan, Y.-m.;
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–E

E
X.-T. Liu et al.
Letter
Synlett
residue was purified by column chromatography on silica gel to
give a white solid; yield: 156 mg (95%); mp 117–119 °C. IR
mixture was stirred at r.t. in air until the reaction was complete
(TLC). Sat. aq Na2S2O3 was added to quench the reaction, and the
mixture was diluted with H2O (10 mL). The aqueous phase was
extracted with EtOAc (3 × 10 mL). The combined organic layers
were dried (Na2SO4), the solvent was removed under vacuum,
and the crude residue was purified by column chromatography
(silica gel) to give a yellow solid; yield: 140 mg (94%); mp 138–
(film): 3461, 3130, 2180, 1598, 1499 cm–1 1H NMR (400 MHz,
.
CDCl3): δ = 1.29 (s, 6 H), 2.41 (s, 3 H), 3.67 (s, 1 H), 6.15 (s, 1 H),
7.26–7.38 (m, 7 H), 7.82 (d, J = 8.0 Hz, 2 H). 13C NMR (100 MHz,
CDCl3): δ = 21.5, 27.0, 53.2, 83.3, 91.7, 122.4, 128.2, 128.3,
128.3, 129.3, 131.7, 135.3, 143.8. HRMS (ESI): m/z [M + H]+ calcd
for C18H21N2O2S: 329.1318; found: 329.1320.
140 °C. IR (film): 3102, 1597, 1489 cm–1 1H NMR (400 MHz,
.
4-Iodo-3,3-dimethyl-5-phenyl-3H-pyrazole (4a)
CDCl3): δ = 1.47 (s, 6 H), 7.47–7.53 (m, 3 H), 8.26–8.28 (m, 2 H).
13C NMR (100 MHz, CDCl3): δ = 21.3, 97.5, 111.3, 128.2, 128.5,
129.5, 130.6, 154.0. HRMS (ESI): m/z [M + H]+ calcd for
Propargyl hydrazide 3a (164 mg, 0.5 mmol), I2 (381 mg, 1.5
mmol), and NaHCO3 (126 mg, 1.5 mmol) were added to a 10 mL
round-bottomed flask. MeCN (5 mL) was added, and the
C
11H12IN2: 299.0040; found: 299.0042.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–E