Mendeleev Commun., 2019, 29, 378–379
Ar
i
R
C
C
electron-neutral and electron-deficient aryl iodides 2a–g reacted
with phenylacetylene 1a to afford the corresponding diaryl-
acetylenes 3a–g in excellent yields. ortho-Substituted aryl iodide,
1-iodo-2-nitrobenzene 2h, reacted with 1a to give the desired
product 3h in 91% yield. Excellent yields of products 3i–m
were achieved for other alkynes 1b–f and 4-iodoanisole 2a.
Unfortunately, aryl bromides were essentially unreactive (9% of
product was obtained from 4-bromoanisole).
ArI
+
R
C CH
1a R = Ph
3a–m
2a Ar = 4-MeOC6H4
2b Ar = 4-MeC6H4
2c Ar = 3,5-Me2C6H3
2d Ar = 4-F3CC6H4
2e Ar = 4-NCC6H4
2f Ar = 4-O2NC6H4
2g Ar = 4-MeO2CC6H4
2h Ar = 2-O2NC6H4
1b R = 4-MeC6H4
1c R = 4-ClC6H4
1d R = 4-NCC6H4
1e R = n-C6H13
1f R = Cy
3
R
Ar
Yield of 3 (%)
This work was supported by the Russian Foundation for Basic
Research (grant no. 16-33-60207).
a
b
c
d
e
f
g
h
i
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
4-MeOC6H4
4-MeC6H4
3,5-Me2C6H3
4-F3CC6H4
4-NCC6H4
4-O2NC6H4
94
90
89
94
92
97
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4-MeO2CC6H4 93
2-O2NC6H4
4-MeOC6H4
4-MeOC6H4
4-MeOC6H4
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Scheme 1 Reagents and conditions: i, CuI (2.4 mg, 5 mol%), 3-Pphen
(3.9 mg, 5 mol%), ArI (0.25 mmol), alkyne (0.3 mmol), PEG-400 (20 mg,
20 mol%), H2O (1 ml), 100°C, 3 h (or 6 h for 2b,c). Yields after chromato-
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68% (entry 2). Among several bases in the reaction performed
using CuSO4·5H2O/3-Pphen (10 mol%) in the presence of
PEG-400 (20 mol%) (entries 3–5), K2CO3 was found to be most
effective, whereas CuI/3-Pphen system showed higher catalytic
activity, and in this case the reaction was completed in 1 h (entry 6)
.
Meantime, only a trace of product 3a was obtained with unsub-
stituted phenanthroline (entry 11) in contrast to the previously
published results.14 Isomeric diethoxyphosphoryl-1,10-phenan-
throlines, 2-Pphen and 4-Pphen, were less effective ligands than
3-Pphen (entries 12, 13). It is important to note that CuI/3-Pphen
has significantly improved catalytic activity under ‘on water’
conditions in comparison with the reaction in organic solvents
(entries 7, 9, 10) or under neat conditions (entry 8). The use of
smaller amounts of CuI and 3-Pphen (5 mol%) required prolonged
time, but also provided a high yield of the product (entry 14).
Thus, the optimized reaction conditions involve CuI (5 mol%),
3-Pphen (5 mol%), and K2CO3 (2 equiv.) in water at 100°C.
To examine the scope and limitations for the the found catalytic
system, a variety of aryl iodides and terminal alkynes were tested
under the optimized conditions† (see Scheme 1). Electron-rich,
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A. Van Der Lee, J. Mao and M. Taillefer, ChemistrySelect, 2017, 2,
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†
All reactions were carried out under argon atmosphere. All halides and
alkynes were purchased from Aldrich and Alfa. Copper(i) iodide (98%) was
purchased from Alfa. NMR spectra were measured in CDCl3 on a Bruker
Avance-400 spectrometer with TMS as an internal standard. Diethoxy-
phosphoryl-1,10-phenanthrolines were obtained according to the published
method.23
25 A. Y. Mitrofanov, A. G. Bessmertnykh-Lemeune and I. P. Beletskaya,
Inorg. Chim. Acta, 2015, 431, 297.
General procedure of cross-coupling of aryliodides with alkynes. An
8 ml glass vial was charged with the alkyne (0.3 mmol), aryl iodide
(0.25 mmol), K2CO3 (79 mg, 0.5 mmol), CuI (2.4 mg, 5 mol%), 3-Pphen
(3.9 mg, 5 mol%), PEG-400 (20 mg, 20 mol%) and water (1 ml) under
argon. The vial was closed with a Teflon cap and the heterogeneous
reaction mixture was stirred at 100°C for 3 or 6 h (see Scheme 1). After
cooling, the mixture was extracted with EtOAc, the extract was dried over
MgSO4. After evaporation, the residue was purified by flash chromato-
graphy on silica gel with light petroleum as the eluent. 1H and 13C NMR
spectroscopic data of products were consistent with those described
previously.13
Received: 9th January 2019; Com. 19/5798
– 379 –