Synthesis of biphenyl-4,4′-diylbis(naphthalene-1-ylmethanone) via carbonylative coupling

Article abstract of DOI:10.14233/ajchem.2015.18819

More recently, an interest has been developed in three component carbonylation reactions, such as the carbonylative Suzuki, carbonylative Sonogashira and carbonylative Heck reactions, which allow for a significant increase in molecular complexity. To develop a luminescent material with high colour purity, luminous efficiency and stability, we synthesized diketone by carbonylative Suzuki coupling in the presence of Pd(NHC)(NHC=N-heterocyclic carbene) complex as the catalyst. Carbonylative coupling of 4,4′-diiodobiphenyl and naphthalene-1-ylboronic acid was investigated to study the catalytic ability of Pd(NHC) complex. Reactions were carried out using both CO and metal carbonyls. bis(1,3-Dihydro-1,3-dimethyl-2H-imidazol-2-ylidene)diiodopalladium was used as the catalytic complex. Reaction products biphenyl-4,4′-diylbis(naphthalene-1-ylmethanone) 3 and (4′-iodobiphenyl-4yl)(naphthalene-1-yl)methanone 4 were obtained as a result of CO insertion into the palladium(II)-aryl bond. However, when pyridine-4-ylboronic acid was used in place of naphthalene-1-ylboronic acid as the starting reagent, synthetic reaction yielding 3 and 4 were found.

Full text of DOI:10.14233/ajchem.2015.18819

Asian Journal of Chemistry; Vol. 27, No. 8 (2015), 3031-3034
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SIAN
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OURNAL OF HEMISTRY
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http://dx.doi.org/10.14233/ajchem.2015.18819
Synthesis of Biphenyl-4,4'-diylbis(naphthalene-1-ylmethanone) via Carbonylative Coupling
JU HYUN SONG
Department of Chemistry, Dong-A University, 37 Nakdong-Daero 550 beon-gil, Saha-gu, Busan 604 714, Republic of Korea
Corresponding author: Fax: +82 51 2007259; Tel: +82 51 2007255; E-mail: jhsong@dau.ac.kr
Received: 22 October 2014;
Accepted: 24 December 2014;
Published online: 27 April 2015;
AJC-17186
More recently, an interest has been developed in three component carbonylation reactions, such as the carbonylative Suzuki, carbonylative
Sonogashira and carbonylative Heck reactions, which allow for a significant increase in molecular complexity. To develop a luminescent
material with high colour purity, luminous efficiency and stability, we synthesized diketone by carbonylative Suzuki coupling in the
presence of Pd(NHC)(NHC=N-heterocyclic carbene) complex as the catalyst. Carbonylative coupling of 4,4'-diiodobiphenyl and
naphthalene-1-ylboronic acid was investigated to study the catalytic ability of Pd(NHC) complex. Reactions were carried out using both
CO and metal carbonyls. bis(1,3-Dihydro-1,3-dimethyl-2H-imidazol-2-ylidene)diiodopalladium was used as the catalytic complex. Reaction
products biphenyl-4,4'-diylbis(naphthalene-1-ylmethanone) 3 and (4'-iodobiphenyl-4yl)(naphthalene-1-yl)methanone 4 were obtained
as a result of CO insertion into the palladium(II)-aryl bond. However, when pyridine-4-ylboronic acid was used in place of naphthalene-
1-ylboronic acid as the starting reagent, synthetic reaction yielding 3 and 4 were found.
Keywords: Carbonylation reaction, Luminescent material, Pd(NHC) complex, 4,4'-Diiodobiphenyl, Naphthalen-1-yl boronic acid.
from ethyl acetate afforded colourless prisms, which after
drying in vacuo at 75 ºC had a melting point of 86.5-88 °C.
Anal. calcd. for C5H9N2I: C, 26.80; H, 4.05; I, 56.64; N, 12.50;
found: C, 26.94; H, 4.12; I, 56.89; N, 12.37.
INTRODUCTION
Aryl ketones are common scaffolds in many natural products
and biologically active small molecules1. a carbonylative coup-
ling method for the synthesis of aryl compounds with CO was
pioneered by Heck et al2. This method is one of the most efficient
and direct routes to synthesize aryl ketones as it forms two carbon-
carbon bonds in a single step, in contrast to the conventional
method of introducing ketone functional group in a stepwise
fashion. Carbonylative coupling has since been further deve-
loped to synthesize a range of carbon nucleophiles3, including
those of tin4, copper5, boron6, zinc7, aluminum8, magnesium9
and silicon10. Our purpose is to synthesize a new distyryl
biphenyl arylene (DBA) derivative as a blue-emitting material.
To develop such a luminescent material with high colour purity,
luminous efficiency and stability, first of all, we synthesized
diketone with Pd(NHC) complex as a catalyst under a balloon
of CO or metal carbonyl.
bis(1,3-Dihydro-1,3-dimethyl-2H-imidazol-2-ylidene)-
diiodopalladium: A solution of [Pd(OAc)2] (2 g, 8.9 mmol)
and 1,3-dimethylimidazolium iodide (4.20 g, 18.7 mmol) in
THF (150 mL) was heated for 0.5 h under reflux, during which
time the initially brown solution bleached to yellow. After
evaporation to dryness under vacuum, the residue was washed
with diethyl ether (3 × 50 mL), taken up in CH2Cl2 (100 mL)
and the solution layered with n-pentane (200 mL). At 25 ºC
bis(1,3-dihydro-1,3-dimethyl-2H-imidazol-2-ylidene)diiodo-
palladium crystallized as a yellow solid that was highly soluble
in CHCl3 and slightly soluble in THF and toluene.Yield: 3.70 g
1
(75 %), H NMR (400 MHz, CDCl3, 20 ºC): δ 7.24 (s, 4H,
NCH), 3.92 (s, 12H, CH3); 13C NMR (100 MHz, CDCl3, 20 ºC):
δ 168.2 (carbene-C), 122.3 (NHC), 38.2 (CH3); correct C, H,
N analysis.
EXPERIMENTAL
Carbonylative coupling reaction under carbon monoxide:
In a typical reaction, Pd(NHC) complex (2 × 10-3 g, 5 × 10-2 mol)
was dissolved in 15 mL anisole under N2 gas.After the forma-
tion of a pale brown homogeneous solution, naphthaln-1-
ylboronic acid (2) (0.118 g, 1.0 × 10-3 mol), 4,4'-diiodobiphenyl
(1) (0.203 g, 5 × 10-4 mol) and potassium carbonate (0.425 g,
1.5 × 10-3 mol) were added. The atmosphere was changed to
1,3-Dimethylimidazolium iodide: To a solution of 10.2 g
(0.12 mol) of 1-methylimidazole in 60 mL, of ethyl acetate
was added 43.4 g (0.306 mol) of methyl iodide. The mixture
was refluxed overnight and yellow oil separated during the
course of the reaction. After cooling, the oil solidified giving
26.9 g (98.8 %) of a hygroscopic solid. Two recrystallizations

3032 Song
Asian J. Chem.
carbon monoxide and the reaction mixture was kept at 80 ºC
for 24 h.After elimination of Pd(NHC) complex by filteration.
The reaction mixture was diluted with water (10 mL) and
CH2Cl2 (20 mL). The neutralized solution was extracted with
CH2Cl2. The organic layer was dried (Na2SO4), filtered and
concentrated. The reaction mixture was analyzed immediately
by GC-MS. The residue was chromatographed on a silica gel
(n-hexane : ethyl acetate = 20 : 1, v/v) yield 3 (0.141 g, 61.2
%) and 4 (3.9 × 10-2 g, 18 %).
Carbonylative coupling reaction under metal carbonyl:
The mixture of 4,4'-diiodobiphenyl (1) (0.203 g, 5 × 10-4 mol),
naphthalene-1-ylboronic acid (2) (0.118 g, 1 × 10-3 mol), K2CO3
(0.425 g, 1.5 × 10-3 mol) and di-(1,3-dihydro-1,3-dimethyl-
2H-imidazol-2-ylidene)diiodopalladium (2 × 10-3 g, 5 × 10-2
mol) and molybdenum hexacarbonyl (9.2 × 10-2 mol, 0.7 eq)
was stirred in 15 mL anisole under N2. The reaction mixture
was kept at 80 ºC for 24 h.After elimination of Pd(NHC) complex
by filteration, the reaction mixture was diluted with water (10 mL)
and CH2Cl2 (20 mL). The neutralized solution was extracted
with CH2Cl2. The organic layer was dried (Na2SO4), filtered
and concentrated. The reaction mixture was analyzed imme-
diately by GC-MS. The residue was chromatographed on a silica
gel (n-hexane : ethyl acetate = 20 : 1, v/v) yield 3 (5.5 × 10-2 g,
23.8 %) and 4 (4.7 × 10-2 g, 21.6 %).
RESULTS AND DISCUSSION
During the course of an on-going synthetic project for
preparing aryl ketones, we decided to evaluate the applicability
of N-heterocyclic carbene (NHC) ligands. N-Heterocyclic
carbene ligands have gained popularity in metal-catalyzed
cross-coupling reactions for several reasons11: (1) the steric
bulk that they introduce around the metal center facilitates
reductive elimination; (2) their strong s-donating character
enables facile oxidative addition and (3) their greater stability
at elevated temperatures relative to phosphine-ligands enables
their use under a broader range of reaction conditions. The
synthetic method for producing bis(1,3-dihydro-1,3-dimethyl-
2H-imidazol-2-ylidene)diiodo palladium catalyst is as follows:
N,N'-dimethyl imidazolium iodide was obtained by the reaction
of N-methylimidazole with methyl iodide. Following this,
reaction of N,N'-dimethyl imidazolium iodide with palladium
acetate resulted in NHC-Pd complex in good yield (75 %).
Carbonylative Suzuki coupling using the synthesized NHC-
Pd complex was carried out under a balloon of CO or metal
carbonyls. To study the scope of the process, the reaction condi-
tions were optimized for the cross-coupling of 4,4'-diiodobi-
phenyl and naphthalene-1-ylboronic acid with N-heterocyclic
carbene (NHC) ligand under a balloon (1 atm) of CO or metal
carbonyls. 4,4'-Diiodobiphenyl (1) and naphthalene-1-ylboronic
acid (2) were reacted under CO (1 bar, a balloon) atmosphere
in the presence of the Pd(NHC) complex catalyst formed in
situ12. The desired carbonylative products biphenyl-4,4'-
diylbis(naphthalene-1-ylmethanone) (3) and (4'-iodobiphenyl-
4-yl)(naphthalene-1-yl)methanone (4) were formed in all
cases; irrespective of the reaction conditions.
Biphenyl-4,4'-diylbis-(naphthalene-ylmethanone) (3):
Yield: 23.8 %; m.p.: 243-244 ºC; 1H NMR (200 MHz, CDCl3):
δ (ppm) 8.01 (m, 7H), 7.75 (m, 4H), 7.51 (m, 6H); 13C NMR
(50 MHz, CDCl3): δ (ppm) 197.5, 144.5, 137.3, 134.3, 132.1,
130.8, 129.8, 128.5, 127.5, 120.3; GC/MS m/z 462 (M+);Anal.
Calcd. for C34H22O2: C, 88.29; H, 4.79; O, 6.92; found: C,
88.22; H, 4.81; O, 6.96.
When metal carbonyl [for Mo(CO)6: 3 = 23.6 % and 4 =
21.5 %; Mn2(CO)10 : 3 = 24.6 % and 4 = 11.1 %; Co2(CO)8 : 3 =
5.7 % and 4 = 18.2 %; Fe(CO)5 : 3 = 28.6 % and 4 = 12.7 %;
Fe3(CO)12 : 3 = 3.2 % and 4 = 20.9 %] was used in place of CO (3
= 30.6 % and 4= 12.7 %), we achieved the same reaction products.
(4'-Iodobiphenyl-4-yl)(naphthalene-1-yl)methanone
(4): Yield: 21.6 %; m.p.: 215-216 ºC; H NMR (200 MHz,
CDCl3): δ (ppm) 7.93 (m, 5H), 7.55 (m, 4H); GC/MS m/z 434
(M+); Anal. Calcd. for C23H15IO: C, 63.61; H, 3.48; I, 29.22;
O, 3.68; found: C, 63.57; H, 3.46; I, 29.22; O, 3.70.
1
O
CO(1 atm)
1 mol % Pd(NHC)
3
4
O
+
I
I
+
OH
OH
K2CO3 (0.7 eq)
Anisole (0.1 M)
80 °C
B
O
1
2
O
I
3
4
Metal Carbonyl
1 mol %Pd(NHC)
O
+
I
I
+
OH
K2CO3 (0.7 eq)
Anisole (0.1 M)
80 °C
O
B
OH
1
2
I

Vol. 27, No. 8 (2015)
Synthesis of Biphenyl-4,4'-diylbis(naphthalene-1-ylmethanone) via Carbonylative Coupling 3033
TABLE-1
CARBONYLATIVE SUZUKI COUPLING WITH NAPHTHALENE-1-YLBORONIC ACID AND 4,4’-DIIODOBIPHENYL
Yield (%)
Run
Iodide
Boronic acid
CO
Reaction time (h)
3
4
1
2
3
4
5
6
CO
24
24
24
24
24
24
61.2
23.8
24.6
5.7
28.6
3.2
18.0
21.6
11.11
18.2
12.7
20.9
Mo(CO)6
Mn2(CO)10
Co2(CO)8
Fe(CO)5
Fe3(CO)12
OH
B
OH
I
I
O
I
I
1
[PdLn]
.
O
3
I
LnPd
PdLn
I
O
C
O
C
LnPd
PdLn
CO or
Metal Carbonyl
OH
OH
I
(OC)LnPd
PdLn(CO)
I
B
O
O
C
2
¤½
I
LnPd
C
PdLn
I
Scheme-I: Simplified catalytic cycle showing the formation of 3
In reactions with Co2(CO)8 and Fe3(CO)12 as metal carbonyls,
yield of 4 was higher than that of 3 as seen in Table-1. Various
metal carbonyls were as effective as CO donors as CO itself.
The plausible mechanism of diketone formation is assumed
to be as shown in Scheme-I.
It is assumed that the two reactions needed to obtain 3
require a longer reaction time as 4 is formed as a reaction
intermediate. When pyridine-4-ylboronic acid is used in place
of naphthalene-1-ylboronic acid 2, carbonylative Suzuki
coupling under CO or metal carbonyls [Mo(CO)6, Mn2(CO)10,
Co2(CO)8, Fe(CO)5 and Fe3(CO)12] is found not to occur. In
future, we intend to synthesize various diketones by using
hetero aromatic boronic acid to develop a luminescent material.
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ThisworkwassupportedbythegrantfromDong-AUniversity
(2013).

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