Suzuki cross-coupling method to prepare 4,4″-diamino-p-terphenyl

Article abstract of DOI:10.1080/00397910500521845

The synthesis of 4,4″-dinitro-p-terphenyl is accomplished by double Suzuki cross-coupling. The product was reduced catalytically to give 4,4″-diamino-p-terphenyl in 75% overall yield. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910500521845

Synthetic Communicationsw, 36: 1343–1346, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500521845
Suzuki Cross-coupling Method to Prepare
4,400-Diamino-p-terphenyl
Matthew C. Davis
Chemistry & Materials Division, Michelson Laboratory,
Naval Air Warfare Center, China Lake, California, USA
Abstract: The synthesis of 4,400-dinitro-p-terphenyl is accomplished by double Suzuki
cross-coupling. The product was reduced catalytically to give 4,400-diamino-p-
terphenyl in 75% overall yield.
Keywords: Diamino, dinitro, palladium, Suzuki reaction, terphenyl
As part of a project to prepare redox active polymers, 4,400-diamino-p-
terphenyl was required. The compound had been previously synthesized and
studied by Hammond and Pavlopoulos as a laser dye.[1,2] The compound is
available from Lancaster Synthesis (Windham, NH) but is too expensive for
our purposes; 2004–2005 catalog #5403, 5 g/$235 USD. The first step in
Hammond and Pavlopoulos’s synthesis was the mixed-acid nitration of
commercially available para-terphenyl. The 4,400-dinitro-p-terphenyl was
conveniently isolated in pure form directly from the cooled reaction mixture
in 32% yield. The dinitro compound was then reduced with tin and acid in
76% yield, giving the product in 24% overall yield from para-terphenyl. An
alternative method was sought to avoid the low-yielding and nonselective
nitration and to find a reduction procedure that does not require stoichiometric
heavy metals.
Al-Masri et al. previously reported that phenyldiboronic acids
undergo double Suzuki cross-coupling with nitroarylbromides to provide
Received in the USA October 25, 2005
Address correspondence to Matthew C. Davis, Chemistry & Materials Division
(Code 498220D), Michelson Laboratory, Naval Air Warfare Center, China Lake,
California, USA. E-mail: matthew.davis@navy.mil
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M. C. Davis
dinitro-p-terphenylenes.[3] We adopted this strategy with similarly excellent
results (Scheme 1). Coupling between compounds 1 and 2 gave the dinitro
3, which precipitated from the reaction mixture. The residual palladium
contained in 3 was removed by recrystallization from DMF, giving pure
product in 76% yield. The subsequent catalytic reduction of 3 to 4
proceeded without complication in 99% yield.
In conclusion, the synthesis of 4,400-diamino-p-terphenyl has been
updated. This new method employs a double Suzuki cross-coupling
followed by catalytic reduction. The product is provided in 75% overall
yield from commercially available 1,4-phenylenebisboronic acid.
EXPERIMENTAL
Melting points were collected on an electrothermal capillary melting-point
apparatus and are not corrected. NMR spectra were obtained on a Bruker AC-
200 spectrometer (1H at 200MHz, 13C at 50 MHz) and are referenced to solvent
or tetramethylsilane. The following reagents were purchased from Aldrich
Chemical Co. (Milwaukee) and used as received: 1-bromo-4-nitrobenzene
1, 99% tetrahydrofuran (inhibited with 250 ppm BHT), 1,4-phenylenebisboronic
acid 2, and 99% tetrakis(triphenylphosphine)palladium(0). The 5% palladium
on carbon catalyst was purchased from Lancaster Synthesis (Windham, NH).
All other reagents were obtained commercially and used as received.
4,400-Dinitro-p-terphenyl (3)
A 1-L, round-bottomed flask equipped with magnetic stir bar was charged
with 7.6 g of 1,4-phenylenebisboronic acid 1 (0.046 mol, 1 equiv), 18.55 g
Scheme 1. Reagents and conditions: a) Pd(PPh3)4, K2CO3, THF, H2O, reflux; b) Pd/C,
THF, H2, 40 psig.

4,400-Diamino-p-terphenyl
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of 1-bromo-4-nitrobenzene 2 (0.092 mol, 2 equiv), 400 mL of THF, and 92 mL
of 2 M K2CO3 (0.184 mol, 4 equiv). A reflux condenser and N2 bubbler were
attached, and the mixture was heated gently to dissolve all the solids. Tetra-
kis(triphenylphosphine)palladium(0) (600 mg) was added in one portion,
and the mixture was refluxed for 18 h. The product precipitated from the
reaction mixture as the reaction proceeded. After this time, the mixture was
cooled to rt, and 200 mL of H2O was added. The solids were collected on a
medium-porosity glass frit and washed with 200 mL of H2O. The solids
were transferred to a 500 mL beaker and recrystallized from 250 mL of
DMF. The bright yellow powder was collected on a medium-porosity
glass frit, washed with EtOH, and air dried on the frit (11.2 g, 76%). Mp
270–2728C (lit.[2] 274–2758C). dH (DMSO-d6): 8.35 (d, J ¼ 8.8 Hz, 4H),
8.07 (d, J ¼ 9.0 Hz, 4H), 7.99 (s, 4H); dC (DMSO-d6 at 1258C): 146.70,
145.18, 137.86, 127.38, 127.26, 123.37. Anal. calcd. for C18H12N2O4: C,
67.5; H, 3.78; N, 8.75. Found: C, 67.51; H, 3.62; N, 8.64.
4,400-Diamino-p-terphenyl (4)
A mixture of 26.8 g of 3, 1-L of THF (containing 250 ppm BHT), and 2 g of
5% Pd on carbon catalyst were shaken on a Parrw hydrogenator for 18 h
(40 psig). After 1 h, the reaction mixture appeared orange and opaque. After
18 h, the mixture was colorless. To the reaction mixture were added 500 mL
of hexanes, and then the mixture was filtered through diatomaceous earth
on a coarse glass frit. The addition of hexanes ensured complete removal of
the catalyst by a single filtration; otherwise a small amount of catalyst was
inevitably entrained. The colorless filtrate was rotary evaporated, leaving a
white solid. The material was placed under vacuum to remove residual
solvent (rt, 1 Torr) and was pure by NMR. An analytical sample was made
by recrystallization from MeCN, providing the title compound as small
colorless plates. Mp 240–2418C with decomposition (lit.[4] 248–2538C and
lit.[5] 2408C). The product can also be recrystallized from 1,4-dioxane or
toluene. dH (DMSO-d6): 7.56 (s, 4H), 7.41 (d, J ¼ 8.3 Hz, 4H), 6.69
(d, J ¼ 8.3 Hz, 4H); dC (DMSO-d6): 148.19, 137.96, 127.24, 126.89,
125.63, 114.36. Anal. calcd. for C18H14N2: C, 83.04; H, 6.19; N, 10.76.
Found: C, 82.75; H, 6.21; N, 10.60.
ACKNOWLEDGMENT
Financial support from the Office of Naval Research is gratefully acknowl-
edged. The author thanks Geoffrey A. Lindsay, Naval Air Warfare Center
Weapons Division for advice and encouragement throughout the course of
this work. Thanks to Andrew P Chafin, Naval Air Warfare Center Weapons
Division for comments and suggestions regarding the manuscript.

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M. C. Davis
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dene)diphthalic anhydride. Macromolecules 1999, 32, 7853–7858.
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