Extension studies on iron(III)-promoted free radical oxidation of anilines: Self-coupling and self-bridged assembling reactions

Article abstract of DOI:10.1016/j.tet.2015.06.018

The iron(III)-promoted free radical oxidation of anilines has been further developed. Anilines including those bearing strong electron-withdrawing groups on benzene ring were readily converted into corresponding self-coupling benzidines. With addition of

Full text of DOI:10.1016/j.tet.2015.06.018

Accepted Manuscript
Extension studies on iron(III)-promoted free radical oxidation of anilines: self-coupling
and self-bridged assembling reactions
Jing Pan, Jiaqiang Li, Ruofeng Huang, Xiaohui Zhang, Hang Shen, Yan Xiong,
Xiangming Zhu
PII:
S0040-4020(15)00873-X
10.1016/j.tet.2015.06.018
TET 26853
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 23 January 2015
Revised Date: 2 June 2015
Accepted Date: 3 June 2015
Please cite this article as: Pan J, Li J, Huang R, Zhang X, Shen H, Xiong Y, Zhu X, Extension studies on
iron(III)-promoted free radical oxidation of anilines: self-coupling and self-bridged assembling reactions,
Tetrahedron (2015), doi: 10.1016/j.tet.2015.06.018.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Graphical Abstract
Extension studies on iron(III)-promoted free
radical oxidation of anilines: self-coupling
and self-bridged assembling reactions
Leave this area blank for abstract info.
Jing Pana , Jiaqiang Lia , Ruofeng Huanga , Xiaohui Zhanga , Hang Shena , Yan Xionga, and Xiangming Zhub
a School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030, China.
bUCD School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland.
R3
R3
R3
R3
R1
R1
R2
FeCl3 6H2O
FeCl3 6H2O, Et3N
R1
R1
N
N
N
Toluene, 85 oC
R1 = Me
N
N
R2
Toluene, 85 oC
R2
R
R1
2
R3
R2

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Extension studies on iron(III)-promoted free radical oxidation of anilines: self-
coupling and self-bridged assembling reactions
Jing Pana , Jiaqiang Lia , Ruofeng Huanga , Xiaohui Zhanga , Hang Shena , Yan Xionga, and Xiangming
Zhub
a School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030, China.
b UCD School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
The iron(III)-promoted free radical oxidation of anilines has been further developed. Anilines
including those bearing strong electron-withdrawing groups on benzene ring were readily
converted into corresponding self-coupling benzidines. With addition of base, the methyl on
nitrogen was activated and the free radical oxidations tended to furnish the corresponding self-
bridged assembling diaminodiarylmethanes.
Available online
2009 Elsevier Ltd. All rights reserved
.
Keywords:
Anilines
FeCl3·6H2O
Oxidation
Self-bridged
Self-coupling
———
Corresponding author. Tel.: +86-15086903431; fax: +86-023 65112134; e-mail: xiong@cqu.edu.cn

2
Tetrahedron
ACCEPTED MANUSCRIPT
1. Introduction
iminium intermediate through ClꢁꢁꢁH (-CH3) hydrogen bonding as
in TS1 (Fig. 3). In the presence of crystal water or additional
water, Clꢀ is bonded by water as in TS2, and the former hydrogen
bond is broken. Therefore no iminium intermediate is formed and
give rise to only self-coupling product. When extra NEt3 was
added, either the hydrogen of methyl group is activated by HꢁꢁꢁN
(NEt3) hydrogen bond as in TS3′ or the ClꢁꢁꢁH (H2O) hydrogen
bond is broken to release Cl, which is capable of connecting and
activating the methyl group, through interaction of water and
NEt3 as in TS3. On the basis of above principle, we have gotten
methylene-bridged product in yield of 68%. Here we wish to
obtain the methylene-bridged products in better yield and enlarge
the scope of substrate.
As a consequence of the versatile application of benzidines in
functional material1,2 and immunohistochemistry,3 for instance,
the hole-transport material N,N′-bis(3-methylphenyl)-N,N′-
diphenylbenzidine (TPD) and N,N′-bis(1-naphthyl)-N,N′-
diphenyl-1,1′-biphenyl-4,4′-diamine (NPB),4 and safe staining
reagents 3,3',5,5'-tetramethylbenzidine (TMB),3 numerous
strategies have been exploited to synthesize these benzidines and
derivatives in the past decades.5-13 Traditionally, the acid
catalyzed rearrangement of hydrazobenzenes has been thought to
be the main protocol for the synthesis of several benzidines, but
inevitable byproducts in this reaction and the multi-step synthetic
routes of hydrazobenzenes limit its scope of usage.6 In order to
obtain diversely functionalized benzidines effectively, the direct
self-coupling of anilines employing TiCl4,7 cerium(IV)
ammonium nitrate (CAN),8 CuBr/H2O2,9 Cu(ClO4)2,10 anhydrous
FeCl3,11 FeCl3·6H2O12a and organic 1,8-bis(diphenylmethylium)-
naphthalenediyl dications13 as oxidants have been developed, in
which self-coupling reactions involved either free radical cation
(Path A) or aryl-metal intermediate (Path B) (Fig. 1).
Fig. 1. Free radical (path A) and aryl-metal (Path B) involved
self-coupling of anilines
Fig. 3. Self-coupling reaction and self-bridged assembling
activation model of methyl protected anilines
In FeCl3·6H2O mediated free radical oxidative self-coupling
of anilines, we found that the different substituents at nitrogen
atom affected both reactivity and selectivity largely (Fig. 2).12
For example, unprotected aniline (i) coordinated with
FeCl3·6H2O exhibit no reactivity, and the increased basicity of
N,N-dimethyl substituted aniline (ii) providing desired N,N,N′,N′-
tetramethylbenzidines results in 88% yield. N,N-dibenzylanilines
(iii) improves the selectivity without the loss of reactivity.
However, the ortho-substituents inhibit the self-coupling
reactions due to steric repulsions with dibenzyl substitution.
Monobenzyl substitution (iv) overcomes the steric shielding,
whereas, compared with ii, the decreased basicity of nitrogen in
iii as well as iv are disadvantage for the substitutions such as
fluoro, acetyl, ester and nitro, even no reactivity. As a promising
expectation, different substituents at nitrogen atom would expand
the substrate scope of iron(III)-promoted free radical oxidative
self-coupling reaction. Hence, we turn our attention to methyl
substitution on nitrogen, a stronger electron-donating group, and
wish to enlarge the substrate scope bearing the electron-deficient
benzene ring.
2. Results and discussion
The oxidative self-coupling reaction of N-substituted anilines
was utilized to test the substrate scope (Table 1). Basically, N,N-
dimethylaniline gave the coupling product in yield of 88%.12a It is
noteworthy that the yield was directly depended on steric
hindrance. As a result, N,N,2-trimethylaniline gave desired
coupling product 2a in 44% yield, and no coupling benzidines
were obtained by employing 2-isopropyl-N,N-dimethylaniline,
and 2-(tert-butyl)-N,N-dimethylaniline as substrates. Similiarly,
the remote methyl group substituted at meta-position (1b)
resulted in the yield of 91%, the ethyl group at meta-position
afforded self-coupling product 2c in yield of 84%, and a further
decreased yield of 65% was obtained employing dimethyl
substituted aniline (1d) as substrate.
ortho-Fluro substituted N,N-dimethylaniline generated
product 2e in yield of 49%, whereas 2,3,5,6-tetrafluro N,N-
dimethylaniline gave no desired product, remote meta-fluoro
substituted aniline was effective for this coupling process
obtaining 2f in 84% isolated yield. Rationally, anilines bearing
bulky halo (Cl, Br and I)-substitutions presented slightly lower
reactivity giving corresponding coupling products in 58%, 65%
and 69% yields, respectively (2g-2i). Interestingly, anilines
bearing a strong electron-withdrawing group are tolerated under
present conditions. The ester group provided corresponding
coupling product 2j in 65% yield, and acetyl and nitro group
afforded corresponding 2k and 2l in acceptable yields (36% and
15%). Abided by steric effect, ortho-nitro substituted aniline
gave no coupling product, while ortho-cyano substituted aniline
proceeded readily to achieve coupling benzidine 2m in 19% yield.
Naphthylamine was also suitable for this coupling reaction and
furnished the desired coupling product 2n in yield of 75%.
Heteroaromatic N,N-dimethylpyridin-2-amine was investigated
but no corresponding product was obtained.
Fig. 2. Influence of substituents at nitrogen atom
In FeCl3-mediated methylene-bridged assembling,12a the
basicity of Clꢀ activates the methyl group directly to form

3
Mono-protected anilines were likewise investigated and the
decreased basicity of nitrogen lowered the reactivity of anilines.
ortho-Alkoxy aniline performed a good reactivity affording the
coupling product 2o in 60% yield, N-ethylaniline bearing an
ortho-methyl group underwent the coupling reaction to provide
corresponding product 2p in 28% yield, and N-methyl anilines
bearing halo-substituents such as chlorine and iodine were
presence of 1.0 equiv of additional triethylamine under standard
ACCEPTED MANUSCRIPT
conditions for 3.5 h, assembling diphenylmethane 3a in 88%
yield (Table 2).15 Under the same conditions, monomethyl
protected aniline was a suitable substrate to furnish desired self-
bridged assembling product 3b in 50% isolated yield. N-ethyl-N-
a moderate reactivity giving the
diphenylmethane product 3c with 31% yield. N,N-
methylaniline exhibited
tolerated and generated corresponding benzidine 2q and 2r in 36% dimethylanilines bearing halo-substitutions at the meta-position
and 32% yields, respectively. Bearing ester group, the
correspondingly self-coupling product 2s was obtained in 11%
yield. N-methyl tetrahydroquinoline was also suitable for this
coupling procedure and corresponding 2t was obtained in 59%
yield.
on benzene ring afforded methylene-bridged products 3d-3f in
yields of 42%, 30% and 35%, respectively. However, the self-
bridged assembling reaction did not proceed with naphthylamine
and N-benzyl-N-methylaniline, only corresponding self-coupling
product 2n and 2u were obtained in 67% and 24% yields,
respectively.
Table 1. Self-coupling reactions of functionalized anilinesa
Table 2. Self-bridged assembling reaction of functionalized
methyl protected anilinesa
R2
R2
R1
N
FeCl3 6H2O, Et3N
toluene, 85 oC, 3.5 h
N
N
R2
R1
R1
1g-i, n, u-x
3a-h
2a, 44%
2d, 65%
2g, 58%
2b, 91%
2e, 49%
2h, 65%
2c, 84%
3a, 88%
3b, 50%
3e, 30%
3c, 31%
3f, 35%
F
N
N
N
N
F
3d, 42%
2f, 84%
3g, 0% (2n, 67%)b
3h, 0% (2u, 24%)b
a Reaction conditions: anilines (0.4 mmol), FeCl3·6H2O (1.0 mmol), Et3N (0.4
mmol), toluene (2.0 mL), 85 °C, 3.5 h; isolated yields.
2i, 69%
b Isolated yields of coupling products 2 in parentheses.
To demonstrate the potential application of our synthesized
benzidines in functional materials, 2,2’-diacetyl benzidine 2k was
considered to construct larger conjugated system. As a consequence,
2j, 65%
2k, 36%
2n, 75%
2l, 15%
2o, 60%
2r, 32%
polysubstituted 9,10-dimethyl-2,7-bisdimethaminophenanthrene 4
was assembled through a Clemmensen reduction in the presence of
amalgamated zinc,16 and gratifyingly, an acceptable yield of 26%
was afforded.
2m, 19%b
Scheme
1.
Synthesis
of
9,10-dimethyl-2,7-
bisdimethaminophenanthrene 4.
2p, 28%
2s, 11%
2q, 36%
2t, 59%
3. Conclusion
In conclusion, we have further developed the effective
FeCl3·6H2O-promoted free radical oxidation of anilines for
preparing benzidine derivatives and diaminodiarylmethanes with
wider substrate scope. The substrate scope of the self-coupling
reaction was largely expanded to anilines bearing strong
electronic withdrawing groups. The role of extra organic base
triethylamine orientated the coupling reaction and self-bridged
assembling reaction to some extent.
a
Reaction conditions: anilines (0.4 mmol), FeCl3·6H2O (1.0 mmol), toluene
(2.0 mL), 85 °C, 2 h; isolated yields.
b Reaction time 12 h.
Diarylalkane fragments exhibit in pharmacologically active
compounds and act as key subunits of functional materials. The
self-bridged assembling reactions of anilines were further
examined,14 and the reaction provided the best results in the
4. Experimental section
4.1. General Information

4
Tetrahedron
The 1H and 13C NMR spectra were recorded in CDCl3
4.2.4.
N4,N4,N4',N4',2,2',6,6'-octamethyl-[1,1'-biphenyl]-4,4'-
ACCEPTED MANUSCRIPT
solution at a Bruker Avance 500/125 MHz spectrometer at 20-
25 °C. H NMR chemical shifts were reported in ppm using
tetramethylsilane (TMS, δ = 0.00 ppm) as the internal standard.
The data of H NMR was reported as follows: chemical shift,
diamine (2d)13
1
o
1
White solid; 38.5 mg, 65% yield; mp: 170.5-171.5 C; H
NMR (500 MHz, CDCl3) δ 6.52 (s, 4H), 2.95 (s, 12H), 1.88 (s,
12H); 13C NMR (125 MHz, CDCl3) δ 149.3, 137.2, 129.4, 111.9,
40.9, 20.7; IR (KBr): 2974, 2851, 1608, 1562, 1494, 1442, 1375,
826 cm-1; HRMS (ESI) calcd. for C20H28N2 (M+H)+: 297.2325;
found: 297.2318.
1
multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, m =
multiplet), coupling constant (J values) in Hz and integration. 13
C
NMR spectra were reported in parts per million using solvent
CDCl3 (δ = 77.2 ppm) as an internal standard. All the reagents
used were of analytical grade, purchased locally and used without
any purification unless otherwise specified. Column
chromatographys were performed using silica gel, and analytical
thin-layer chromatography (TLC) which was used to monitor the
reactions was performed on silica gel plates. IR spectra were
recorded on a Nicolet 550II spectrophotometer. HRMS (ESI)
4.2.5. 5,5'-difluoro-N4,N4,N4',N4',2,2'-hexamethyl-[1,1'-biphenyl]-
4,4'-diamine (2e)
o
1
Yellow solid; 29.8 mg, 49% yield; mp: 150.4-151.2 C; H
NMR (500 MHz, CDCl3) δ 6.76 (d, J = 4.5 Hz, 2H), 6.74 (s, 2H),
2.86 (s, 12H), 2.01 (s, 6H); 13C NMR (125 MHz, CDCl3) δ 152.9
(d, J = 242.3), 139.3 (d, J = 8.8 Hz), 133.2 (d, J = 7.5 Hz), 131.8
(d, J = 3.1 Hz), 119.4 (d, J = 3.5 Hz), 117.1 (d, J = 20.5 Hz), 42.9
(d, J = 4.0 Hz), 19.4; IR (KBr): 2948, 2877, 1618, 1555, 1503,
1457, 1388, 1222, 879 cm-1; HRMS (ESI) calcd. for C18H22F2N2
(M+H)+: 305.1824; found: 305.1822.
data were measured on
spectrometer.
a
Agilent
6510 Q-TOF mass
4.2. General Procedure for the oxidative self-coupling
reactions
To a stirred mixture of FeCl3·6H2O (270.3 mg, 1.0 mmol) and
2.0 mL toluene was added aniline 1 (0.4 mmol) at room
temperature. The reaction was stirred at 85 °C for 2 h in
atmosphere. After it was cooled to room temperature, the reaction
mixture was quenched by aqueous ammonia solution (mass
fraction: 25%-28%, 10 mL) and extracted with dichloromethane
(10 mL per time) until no product was observed in the extract,
monitored by TLC. The organic layer was dried over anhydrous
MgSO4, filtered and concentrated under reduced pressure to give
crude product, which was chromatographed on silica gel column
using 1:100 to 1:70 (v/v) EtOAc-petroleum ether solutions as
eluent to afford isolated product 2.
4.2.6. 2,2'-difluoro-N4,N4,N4',N4'-tetramethyl-[1,1'-biphenyl]-4,4'-
diamine (2f)
o
1
White solid; 46.4 mg, 84% yield; mp: 198.5-199.5 C; H
NMR (500 MHz, CDCl3) δ 7.23-7.20 (m, 2H), 6.53 (dd, J1 = 8.5
Hz, J2 = 2.0 Hz, 2H), 6.49-6.47 (m, 2H), 2.97 (s, 12H); 13C NMR
(125 MHz, CDCl3) δ 161.0 (d, J = 243.8 Hz), 151.4 (t, J = 5.6
Hz), 131.9 (t, J = 4.0 Hz), 111.6 (d, J = 14.6 Hz), 108.2, 99.7 (dt,
J1 = 27.3 Hz, J2 = 7.5 Hz), 40.6; IR (KBr): 3047, 2894, 1627,
1548, 1512, 1442, 1364, 1139, 798 cm-1; HRMS (ESI) calcd. for
C16H18F2N2 (M+H)+: 277.1511; found: 277.1507.
4.2.7.
4,4'-diamine (2g)
2,2'-dichloro-N4,N4,N4',N4'-tetramethyl-[1,1'-biphenyl]-
4.2.1. N4,N4,N4',N4',3,3'-hexamethyl-[1,1'-biphenyl]-4,4'-diamine
(2a)
o
1
White solid; 35.9 mg, 58% yield; mp: 147.7-148.4 C; H
NMR (500 MHz, CDCl3) δ 7.12 (d, J = 8.5 Hz, 2H), 6.78 (d, J =
2.5 Hz, 2H), 6.64 (dd, J1 = 8.5 Hz, J2 = 2.5 Hz, 2H), 2.97 (s,
12H); 13C NMR (125 MHz, CDCl3) δ 150.7, 134.9, 132.3, 126.3,
112.6, 110.6, 40.5; IR (KBr): 3036, 2988, 1609, 1504, 1443,
1358, 835, 801 cm-1; HRMS (ESI) calcd. for C16H18Cl2N2
(M+H)+: 309.0920; found: 309.0923.
o
1
White solid; 23.6 mg, 44% yield; mp: 73.2-74.2 C; H NMR
(500 MHz, CDCl3) δ 7.40 (s, 2H), 7.39 (d, J = 8.5 Hz, 2H), 7.11
(d, J = 8.0 Hz, 2H), 2.77 (s, 12H), 2.42 (s, 6H); 13C NMR (125
MHz, CDCl3) δ 151.8, 135.5, 132.3, 129.9, 124.9, 118.7, 44.5,
18.8; IR (KBr): 3003, 2938, 2856, 1606, 1580, 1490, 1450, 1370,
819 cm-1; HRMS (ESI) calcd. for C18H24N2 (M+H)+: 269.2012;
found: 269.2010.
4.2.8.
4,4'-diamine (2h)
2,2'-dibromo-N4,N4,N4',N4'-tetramethyl-[1,1'-biphenyl]-
4.2.2. N4,N4,N4',N4',2,2'-hexamethyl-[1,1'-biphenyl]-4,4'-diamine
(2b)
o
1
White solid; 51.8 mg, 65% yield; mp: 174.4-175.6 C; H
NMR (500 MHz, CDCl3) δ 7.09 (d, J = 8.5 Hz, 2H), 6.96 (d, J =
2.5 Hz, 2H), 6.68 (dd, J1 = 8.5 Hz, J2 = 2.5 Hz, 2H), 2.97 (s,
12H); 13C NMR (125 MHz, CDCl3) δ 150.7, 132.0, 130.1, 125.5,
115.5, 111.0, 40.5; IR (KBr): 3034, 2896, 1605, 1498, 1441,
1350, 832, 602 cm-1; HRMS (ESI) calcd. for C16H18Br2N2
(M+H)+: 396.9910; found: 396.9894.
o
1
White solid; 48.8 mg, 91% yield; mp: 79.7-80.4 C; H NMR
(500 MHz, CDCl3) δ 6.99 (d, J = 7.0 Hz, 2H), 6.64 (s, 2H), 6.62
(dd, J1 = 8.5 Hz, J2 = 2.0 Hz, 2H), 2.96 (s, 12H), 2.06 (s, 6H); 13
C
NMR (125 MHz, CDCl3) δ 149.7, 137.3, 130.9, 130.6, 114.0,
110.1, 40.9, 20.7; IR (KBr): 3036, 2921, 2853, 1608, 1551, 1501,
1442, 1351, 834, 817 cm-1; HRMS (ESI) calcd. for C18H24N2
(M+H)+: 269.2012; found: 269.2000.
4.2.3. 2,2'-diethyl-N4,N4,N4',N4'-tetramethyl-[1,1'-biphenyl]-4,4'-
diamine (2c)
4.2.9. 2,2'-diiodo-N4,N4,N4',N4'-tetramethyl-[1,1'-biphenyl]-4,4'-
diamine (2i)
o
1
White solid; 67.9 mg, 69% yield; mp: 201.1-203.0 C; H
NMR (500 MHz, CDCl3) δ 7.22 (d, J = 2.5 Hz, 2H), 7.03 (d, J =
8.5 Hz, 2H), 6.73 (dd, J1 = 8.5 Hz, J2 = 2.5 Hz, 2H), 2.97 (s,
12H); 13C NMR (125 MHz, CDCl3) δ 150.5, 137.4, 130.7, 121.7,
111.8, 102.7, 40.5; IR (KBr): 3033, 2962, 1596, 1497, 1441,
1357, 804, 538 cm-1; HRMS (ESI) calcd. for C16H18I2N2 (M+H)+:
492.9632; found: 492.9633.
o
1
White solid; 49.8 mg, 84% yield; mp: 78.3-80.0 C; H NMR
(500 MHz, CDCl3) δ 6.99 (d, J = 8.5 Hz, 2H), 6.67 (d, J = 2.5 Hz,
2H), 6.61 (dd, J1 = 8.5 Hz, J2 = 2.5 Hz, 2H), 2.97 (s, 12H), 2.48-
2.32 (m, 4H), 1.05 (t, J = 7.5 Hz, 6H); 13C NMR (125 MHz,
CDCl3) δ 149.8, 143.4, 131.3, 129.8, 112.4, 110.0, 40.9, 27.0,
15.6; IR (KBr): 3033, 2963, 2932, 2868, 1608, 1553, 1497, 810
cm-1; HRMS (ESI) calcd. for C20H28N2 (M+H)+: 297.2325; found:
297.2327.
4.2.10. dimethyl 4,4'-bis(dimethylamino)-[1,1'-biphenyl]-2,2'-
dicarboxylate (2j)
o
1
Green solid; 46.3 mg, 65% yield; mp: 144.2-145.0 C; H NMR
(500 MHz, CDCl3) δ 7.27 (d, J = 3.0 Hz, 2H), 7.07 (d, J = 8.5 Hz,

5
2H), 6.86 (dd, J1 = 8.5 Hz, J2 = 3.0 Hz, 2H), 3.62 (s, 6H), 3.01 (s,
809 cm-1; HRMS (ESI) calcd. for C18H24N2 (M+H)+: 269.2012;
found: 269.2017.
ACCEPTED MANUSCRIPT
12H); 13C NMR (125 MHz, CDCl3) δ 168.9, 149.2, 131.8, 131.2,
130.7, 115.4, 113.5, 52.0, 40.7; IR (KBr): 2946, 1723, 1608,
1557, 1500, 1446, 1363,1230, 859 cm-1; HRMS (ESI) calcd. for
C20H24N2O4 (M+H)+: 357.1809; found: 357.1806.
4.2.17.
diamine (2q)
2,2'-dichloro-N4,N4'-dimethyl-[1,1'-biphenyl]-4,4'-
o
1
White solid; 20.2 mg, 36% yield; mp: 103.4-104.2 C; H
NMR (500 MHz, CDCl3) δ 7.06 (d, J = 8.0 Hz, 2H), 6.69 (d, J =
2.5 Hz, 2H), 6.53 (dd, J1 = 8.5 Hz, J2 = 2.5 Hz, 2H), 3.83 (brs,
2H), 2.86 (s, 6H); 13C NMR (125 MHz, CDCl3) δ 149.5, 134.8,
132.3, 127.1, 112.1, 110.8, 30.6; IR (KBr): 3434, 2865, 1613,
1560, 1505, 1430, 1312, 810, 611 cm-1; HRMS (ESI) calcd. for
C14H14Cl2N2 (M+H)+: 281.0607; found: 281.0608.
4.2.11.
diyl)bis(ethan-1-one) (2k)
1,1'-(4,4'-bis(dimethylamino)-[1,1'-biphenyl]-2,2'-
o
1
White solid; 23.4 mg, 36% yield; mp: 130.9-131.9 C; H
NMR (500 MHz, CDCl3) δ 7.03 (d, J = 9.0 Hz, 2H), 6.92 (d, J =
2.5 Hz, 2H), 6.80 (dd, J1 = 8.5 Hz, J2 = 3.0 Hz, 2H), 3.01 (s,
12H), 2.10 (s, 6H); 13C NMR (125 MHz, CDCl3) δ 204.6, 149.7,
141.2, 132.2, 127.6, 114.8, 111.8, 40.6, 30.1; IR (KBr): 2856,
1680, 1605, 1541, 1497, 1445, 1360, 816 cm-1; HRMS (ESI)
calcd. for C20H24N2O2 (M+H)+: 325.1911; found: 325.1912.
4.2.18. 2,2'-diiodo-N4,N4'-dimethyl-[1,1'-biphenyl]-4,4'-diamine
(2r)
o
1
White solid; 30.3 mg, 32% yield; mp: 114.5-115.6 C; H
NMR (500 MHz, CDCl3) δ 7.14 (d, J = 2.5 Hz, 2H), 6.98 (d, J =
8.5 Hz, 2H), 6.62 (dd, J1 = 8.5 Hz, J2 = 2.5 Hz, 2H), 3.82 (brs,
2H), 2.85 (s, 6H); 13C NMR (125 MHz, CDCl3) δ 149.2, 138.2,
130.7, 121.4, 112.2, 102.2, 30.6; IR (KBr): 3405, 3034, 2873,
1599, 1557, 1493, 1425, 1317, 830, 479 cm-1; HRMS (ESI) calcd.
for C14H14I2N2 (M+H)+: 464.9319; found: 464.9333.
4.2.12. N4,N4,N4',N4'-tetramethyl-2,2'-dinitro-[1,1'-biphenyl]-4,4'-
diamine (2l)
o
1
White solid; 10.0 mg, 15% yield; mp: 238.5-239.4 C; H
NMR (500 MHz, CDCl3) δ 7.36 (d, J = 3.0 Hz, 2H), 7.09 (d, J =
8.5 Hz, 2H), 6.89 (dd, J1 = 8.5 Hz, J2 = 2.5 Hz, 2H), 3.06 (s,
12H); 13C NMR (125 MHz, CDCl3) δ 150.2, 149.1, 132.3, 120.9,
116.2, 107.3, 40.5; IR (KBr): 2853, 1625, 1522, 1443, 1360,
1340, 819 cm-1; HRMS (ESI) calcd. for C16H18N4O4 (M+H)+:
331.1401; found: 331.1406.
4.2.19. dimethyl 4,4'-bis(methylamino)-[1,1'-biphenyl]-2,2'-
dicarboxylate (2s)
White solid; 7.2 mg, 11% yield; mp: 117.6-117.9 oC; 1H NMR
(500 MHz, CDCl3) δ 7.15 (d, J = 3.0 Hz, 2H), 7.02 (d, J = 8.5 Hz,
2H), 6.74 (dd, J1 = 8.5 Hz, J2 = 2.5 Hz, 2H), 3.82 (brs, 2H), 3.62
(s, 6H), 2.89 (s, 6H); 13C NMR (125 MHz, CDCl3) δ 168.3, 147.5,
132.2, 131.7, 130.6, 115.6, 113.4, 51.8, 30.9; IR (KBr): 3428,
2986, 2887, 1723, 1608, 1557, 1500, 1446, 1363, 1230, 799 cm-1;
HRMS (ESI) calcd. for C18H20N2O4 (M+H)+: 329.1496; found:
329.1485.
4.2.13.
dicarbonitrile (2m)
4,4'-bis(dimethylamino)-[1,1'-biphenyl]-3,3'-
o
1
White solid; 11.1 mg, 19% yield; mp: 157.6-158.4 C; H
NMR (500 MHz, CDCl3) δ 7.63 (d, J = 2.0 Hz, 2H), 7.54 (dd, J1
= 9.0 Hz, J2 = 2.5 Hz, 2H), 6.93 (d, J = 9.0 Hz, 2H), 3.10 (s, 12H);
13C NMR (125 MHz, CDCl3) δ 154.0, 132.4, 131.2, 129.7, 119.6,
117.2, 101.0, 43.0; IR (KBr): 3052, 2853, 2212, 1610, 1506,
1460, 1350, 812 cm-1; HRMS (ESI) calcd. for C18H18N4 (M+H)+:
291.1604; found: 291.1614.
4.2.20. 1,1'-dimethyl-1,1',2,2',3,3',4,4'-octahydro-6,6'-biquinoline
(2t)
4.2.14.
N4,N4,N4',N4'-tetramethyl-[1,1'-binaphthalene]-4,4'-
o
1
Yellow solid; 34.5 mg, 59% yield; mp: 114.2-114.7 C; H
NMR (500 MHz, CDCl3) δ 7.25 (dd, J1 = 8.5 Hz, J2 = 2.5 Hz,
2H), 7.14 (d, J = 2.0 Hz, 2H), 6.63 (d, J = 8.5 Hz, 2H), 3.22 (t, J
= 6.0 Hz, 4H), 2.90 (s, 6H), 2.82 (t, J = 6.5 Hz, 4H), 2.03-1.98 (m,
4H); 13C NMR (125 MHz, CDCl3) δ 145.3, 129.8, 126.9, 124.9,
123.0, 111.4, 51.4, 39.3, 28.0, 22.6; IR (KBr): 3024, 2936, 2862,
1611, 1502, 1461, 1320, 809 cm-1; HRMS (ESI) calcd. for
C20H24N2 (M+H)+: 293.2012; found: 293.2014.
diamine (2n)7
o
1
White solid; 50.8 mg, 75% yield; mp: 132.3-133.4 C; H
NMR (500 MHz, CDCl3) δ 8.33 (d, J = 8.0 Hz, 2H), 7.46 (t, J =
8.5 Hz, 2H), 7.41 (d, J = 8.5 Hz, 2H), 7.38 (d, J = 7.5 Hz, 2H),
7.25 (t, J = 8.5 Hz, 2H), 7.16 (d, J = 8.0 Hz, 2H), 2.98 (s, 12H);
13C NMR (125 MHz, CDCl3) δ 150.6, 134.5, 133.6, 128.9, 128.1,
127.4, 125.8, 125.1, 124.4, 113.7, 45.5; IR (KBr): 3036, 2865,
1611, 1579, 1507, 1476, 1454, 1378, 845 cm-1; HRMS (ESI)
calcd. for C24H24N2 (M+H)+: 341.2012; found: 341.2017.
4.3. General Procedure for the oxidative self-bridged
assembling reactions
4.2.15.
4,4'-diamine (2o)
2,2',5,5'-tetramethoxy-N4,N4'-dimethyl-[1,1'-biphenyl]-
To a stirred mixture of aniline 1 (0.4 mmol) and 2.0 mL
toluene was added triethylamine (56 ꢂL, 0.4 mmol) and
FeCl3·6H2O (270.3 mg, 1.0 mmol) successively at room
temperature. The reaction was stirred at 85 °C for 3.5 h in
atmosphere. After it was cooled to room temperature, the reaction
mixture was quenched by aqueous ammonia solution (mass
fraction: 25%-28%, 10 mL) and extracted with dichloromethane
(10 mL per time) until no product was observed in the extract,
monitored by TLC. The organic layer was dried over anhydrous
MgSO4, filtered and concentrated under reduced pressure to give
crude product, which was chromatographed on silica gel column
using 1:100 to 1:70 (v/v) EtOAc-petroleum ether solution as
eluent to afford isolated product 3.
o
1
White solid; 39.9 mg, 60% yield; mp: 149.8-151.7 C; H NMR
(500 MHz, CDCl3) δ 6.73 (s, 2H), 6.32 (s, 2H), 4.26 (brs, 2H),
3.79 (s, 6H), 3.75 (s, 6H), 2.90 (s, 6H); 13C NMR (125 MHz,
CDCl3) δ 152.0, 140.9, 139.2, 114.9, 113.6, 96.1, 56.9, 56.1, 30.5;
IR (KBr): 3439, 3016, 2879, 1616, 1520, 1483, 1465, 1210, 1040
cm-1; HRMS (ESI) calcd. for C18H24N2O4 (M+H)+: 333.1809;
found: 333.1797.
4.2.16. N4,N4'-diethyl-3,3'-dimethyl-[1,1'-biphenyl]-4,4'-diamine
(2p)
o
1
White solid; 15.0 mg, 28% yield; mp: 94.5-95.8 C; H NMR
(500 MHz, CDCl3) δ 7.32 (d, J = 8.0 Hz, 2H), 7.26 (s, 2H), 6.66
(d, J = 8.5 Hz, 2H), 3.49 (brs, 2H), 3.23 (q, J = 7.0 Hz, 4H), 2.19
(s, 6H), 1.32 (t, J = 7.0 Hz, 2H); 13C NMR (125 MHz, CDCl3) δ
145.1, 130.6, 128.5, 125.1, 122.2, 110.2, 38.8, 17.8, 15.2; IR
(KBr): 3448, 3027, 2969, 2925, 2854, 1610, 1506, 1467, 1369,
4.3.1. 4,4'-methylenebis(N,N-dimethylaniline) (3a)12a,c
o
1
White solid; 29.8 mg, 88% yield; mp: 90.0-91.0 C; H NMR
(500 MHz, CDCl3) δ 7.05 (d, J = 9.0 Hz, 4H), 6.68 (d, J = 8.5 Hz,
4H), 3.80 (s, 2H), 2.89 (s, 12H); 13C NMR (125 MHz, CDCl3) δ

6
Tetrahedron
149.3, 130.5, 129.6, 113.2, 41.1, 40.1; IR (KBr): 3005, 2888,
10 min, the solution was decanted, and amalgamated zinc was
ACCEPTED MANUSCRIPT
1614, 1522, 1444, 1343, 795 cm-1; HRMS (ESI) calcd. for
C17H23N2 (M+H)+: 255.1856; found: 255.1863.
obtained.
4.4.2 Clemmensen reduction of 2k16
4.3.2. 4,4'-methylenebis(N-methylaniline) (3b)
To freshly prepared amalgamated zinc was added
diacetyldiphenyl 2k (65 mg , 0.2 mmol), H2O (280 µL, 15.6 mmol)
and con. hydrochloric acid (720 µL, 23.3 mmol) successively. The
resulting mixture was boiled under reflux for 2 h. The reaction
mixture was washed by diethyl ether (5 mL) and the solid residue
was removed. The solution was alkalized by saturated NaHCO3 and
extracted by diethyl ether (5 mL×3). The organic layers were
combined, dried over anhydrous Mg2SO4, filtered and concentrated
under reduced pressure to give crude product, which was
chromatographed on silica gel column using EtOAc-petroleum
ether (1: 60, v/v) solutions as eluent to afford white solid 4. 15.2
mg, 26% yield; mp: 195.5-196.6 oC; 1H NMR (500 MHz, DMSO)
δ 8.44 (d, J = 8.5 Hz, 2H), 7.16 (d, J = 5.0 Hz, 2H), 7.08 (s, 2H),
3.03 (s, 12H), 2.61 (s, 6H);13C NMR (125 MHz, DMSO) δ 148.1,
131.1, 128.4, 122.8, 120.7, 113.9, 105.1, 40.5, 15.9; ; IR (KBr):
2960, 2924, 1609, 1500, 1430, 1385, 829 cm-1; HRMS (ESI)
calcd. for C20H24N2 (M+H)+ 293.2012, found 293.2005.
o
Slightly yellow solid; 15.1 mg, 50% yield; mp: 55.2-56.2 C;
1H NMR (500 MHz, CDCl3) δ 6.98 (d, J =8.0 Hz, 4H), 6.50 (d, J
= 8.5 Hz, 4H), 3.76 (s, 2H), 3.49 (brs, 2H), 2.74 (s, 6H); 13C
NMR (125 MHz, CDCl3) δ 147.6, 130.9, 129.6, 112.6, 40.2, 31.0;
IR (KBr): 3439, 2926, 2856, 1614, 1521, 1444, 1342, 829 cm-1;
HRMS (ESI) calcd. for C15H18N2 (M+H)+: 227.1543; found:
227.1536.
4.3.3. 4,4'-methylenebis(N-ethyl-N-methylaniline) (3c)
o
Slightly yellow solid; 11.7 mg, 31% yield; mp: 89.6-91.4 C;
1H NMR (500 MHz, CDCl3) δ 7.04 (d, J = 8.5 Hz, 4H), 6.65 (d, J
= 9.0 Hz, 4H), 3.79 (s, 2H), 3.35 (q, J = 7.0 Hz, 4H), 2.86 (s, 6H),
1.09 (t, J = 7.5 Hz, 6H); 13C NMR (125 MHz, CDCl3) δ 147.6,
130.0, 129.7, 112.9, 47.2, 40.0, 37.8, 11.4; IR (KBr): 2918, 2884,
1614, 1522, 1444, 1343, 830 cm-1; HRMS (ESI) calcd. for
C19H26N2 (M+H)+: 283.2169; found: 283.2162.
4.3.4. 4,4'-methylenebis(3-chloro-N,N-dimethylaniline) (3d)11b
Acknowledgments
Slightly yellow solid; 18.1 mg, 42% yield; mp: 99.5-101.1 oC;
1H NMR (500 MHz, CDCl3) δ 6.88 (d, J = 8.5 Hz, 2H), 6.74 (d, J
= 2.5 Hz, 2H), 6.53 (dd, J1 = 9.0 Hz, J2 = 3.0 Hz, 2H), 3.99 (s,
2H), 2.90 (s, 12H); 13C NMR (125 MHz, CDCl3) δ 150.1, 134.9,
131.1, 125.5, 113.2, 111.4, 40.7, 34.9; IR (KBr): 2988, 2853,
1612, 1510, 1445, 1358, 823, 792 cm-1; HRMS (ESI) calcd. for
C17H20Cl2N2 (M+H)+: 323.1077; found: 323.1080.
We gratefully acknowledge funding from the National Natural
Science Foundation of China (No. 21372265 and No. 61271059),
the Scientific Research Fundings of the Scientific Research
Foundation for the Returned Overseas Chinese Scholars, State
Education Ministry, the Natural Science Foundation Project of
CQ CSTC (No. cstc2013jcyjA10037), and the Fundamental
Reseach Funds for the Central Universities (No.
CDJZR14225502 and No. CQDXWL-2013-Z012).
4.3.5. 4,4'-methylenebis(3-bromo-N,N-dimethylaniline) (3e)
o
Slightly yellow solid; 16.5 mg, 30% yield; mp: 97.1-98.7 C;
1H NMR (500 MHz, CDCl3) δ 6.94 (s, 2H), 6.85 (d, J = 8.5 Hz,
2H), 6.58 (d, J = 8.5 Hz, 2H), 4.00 (s, 2H), 2.91 (s, 12H); 13C
NMR (125 MHz, CDCl3) δ 150.2, 130.9, 127.3, 125.8, 116.4,
112.0, 40.7, 40.0; IR (KBr): 2920, 2853, 1608, 1509, 1442, 1360,
805, 500 cm-1; HRMS (ESI) calcd. for C17H20Br2N2 (M+H)+:
411.0066; found: 411.0072.
References and notes
1. (a) Bissell, R. A.; Córdova, E.; Kaifer, A. E.; Stoddart, J.
F. Nature. 1994, 369, 133. (b) Ballardini, R.; Balzani, V.;
Gandolfi, M. T.; Prodi, L.; Venturi, M.; Philip, D.; Ricketts, H.
G.; Stoddart, J. F. Angew. Chem., Int. Ed. 1993, 32, 1301.
2. (a) Sariciftci, N. S.; Smilowitz, L.; Heeger, A. J.; Wudl, F.
Science. 1992, 258, 1474. (b) Johnson, G. E.; McGrane, K. M.;
Stolka, M. Pure Appl. Chem. 1995, 67, 175. (c) Horowitz, G.
Adv. Mater. 1998, 10, 365. (d) O’Brien, D. F.; Burrows, P. E.;
Forrest, S. R.; Koene, B. E.; Loy, D. E.; Thompson, M. E. Adv.
Mater. 1998, 10, 1108. (e) Noda, T.; Ogawa, H.; Noma, N.;
Shirota, Y. J. Mater. Chem. 1999, 9, 2177. (f) Goodbrand, H. B.;
Hu, N.-X. J. Org. Chem. 1999, 64, 670. (g) Getautis, V.;
Stanisauskaite, A.; Paliulis, O.; Uss, S.; Uss, V. J. Prakt. Chem.
2000, 342, 58. (h) Hmadeh, M.; Traboulsi, H.; Elhabiri, M.;
Braunstein, P.; Albrecht-Gary, A.; Siri, O. Tetrahedron, 2008,
64, 6522.
4.3.6. 4,4'-methylenebis(3-iodo-N,N-dimethylaniline) (3f)
Slightly yellow solid; 23.6 mg, 35% yield; mp: 120.2-121.5 oC;
1H NMR (500 MHz, CDCl3) δ 6.94 (s, 2H), 6.84 (d, J = 8.5 Hz,
2H), 6.58 (d, J = 8.5 Hz, 2H), 4.00 (s, 2H), 2.91 (s, 12H); 13C
NMR (125 MHz, CDCl3) δ 150.2, 130.9, 127.3, 125.8, 116.4,
112.0, 40.7, 40.0; IR (KBr): 2918, 2897, 2853, 1607, 1509, 1442,
1359, 824, 443 cm-1. HRMS (ESI) calcd. for C17H20I2N2 (M+H)+:
485.9994; found: 485.9981 (116I, 117I).
3. (a) Holland, V. R.; Saunders, B. C.; Rose, F. L.; Walpole, A. L.
Tetrahedron. 1974, 30, 3299. (b) Liu, L.-F.; Zhang, Y.-L.; Qian,
X.-H. Dyes Pigments. 2004, 60, 17.
4.3.7.
diamine (2u)12a
N4,N4'-dibenzyl-N4,N4'-dimethyl-[1,1'-biphenyl]-4,4'-
4. Khademi, S.; Song, J. Y.; Wyatt, P. B.; Kreouzis, T.; Gillin, W.
P.; Adv. Mater. 2012, 24, 2278.
o
1
White solid; 12.6 mg, 24% yield; mp: 146.0-147.0 C; H
NMR (500 MHz, CDCl3) δ 7.41 (d, J = 8.5 Hz, 4H), 7.32-7.30
(m, 4H), 7.26 (m, 6H), 6.78 (d, J = 8.5 Hz, 4H), 4.54 (s, 4H),
3.03 (s, 6H); 13C NMR (125 MHz, CDCl3) δ 148.5, 139.3, 129.8,
128.7, 127.2, 127.04, 126.95, 112.9, 56.9, 38.8. ; IR (KBr): 3026,
2926, 2891, 1610, 1511, 1450, 1369, 808 cm-1; HRMS (ESI)
calcd. for C28H29N2 (M+H)+ 393.2326, found 393.2331.
5. (a) Nelson, T. D.; Crouch, R. D. Org. React.2004, 63, 265.
6. (a) Cheng, J.-D.; Shine, H. J. J. Org. Chem. 1975, 40, 703. (b)
Gündüz, T.; Kiliç, E.; Kenar, A.; Öztaş, S. G. Analyst. 1989, 114,
727. (c) Zhu-Ohlbach, Q.; Gleiter, R.; Rominger, F.; Schmidt, H.
L.; Reda, T. Eur. J. Org. Chem. 1998, 2409. (d) Buncel, E. Can.
J. Chem. 2000, 78, 1251. (e) Kang, H.-M.; Lim, Y.-K.; Shin, I.-
J.; Kim, H.-Y.; Cho, C.-G. Org. Lett. 2006, 8, 2047. (f) De, C. K.;
Pesciaioli, F.; List, B. Angew. Chem. Int. Ed. 2013, 52, 9293.
7. Periasamy, M.; Jayakumar, K. N.; Bharathi, P. J. Org. Chem.
2000, 65, 3548.
8. (a) Xi, C.-J.; Jiang, Y.-F.; Yang, X.-H. Tetrahedron Lett. 2005,
46, 3909. (b) Yang, X.-H.; Xi, C.-J.; Jiang, Y.-F. Synth. Commun.
2006, 36, 2413.
9. Jiang, Y.-F.; Xi, C.-J.; Yang, X.-H. Synlett 2005, 1381.
10. Kirchgessner, M.; Sreenath, K.; Gopidas, K. R. J. Org. Chem.
2006, 71, 9849.
4.4. General Procedure for the synthesis of 4
4.4.1 Preparation of amalgamated zinc
To a round-bottom flask was added zinc powder (480 mg, 7.3
mmol) and mercuric chloride (48 mg, 0.2 mmol), followed by
H2O (800 µL, 44.4 mmol) and con. hydrochloric acid (24 µL, 0.8
mmol). The reaction mixture was stirred at room temperature for

7
11. (a) Murata, S.; Miura, M.; Nomura, M. J. Chem. Soc., Chem.
ACCEPTED MANUSCRIPT
Commun. 1989, 116. (b) Murata, S.; Miura, M.; Nomura, M. J.
Org. Chem. 1989, 54, 4700. (c) Li, X.-L.; Huang, J.-H.; Yang,
L.-M. Org. Lett. 2011, 13, 4950.
12. (a) Ling, X.-G.; Xiong, Y.; Huang, R-F.; Zhang, X-H.; Zhang, S-
T.; Chen, C.-G. J. Org. Chem. 2013, 78, 5218. Also see: (b) Li,
H.-J.; He, Z.-H.; Guo, X.-W.; Li, W.-J.; Zhao, X.-H.; Li, Z. Org.
Lett. 2009, 11, 4176. (c) Zhang, L.; Peng, C.; Zhao, D.; Wang, Y.;
Fu, H.-J.; Shen, Q.; Li, J-X. Chem. Commun. 2012, 48, 5928.
13. (a) Saitoh, T.; Yoshida, S.; Ichikawa, J. Org. Lett. 2004, 6, 4563.
(b) Saitoh, T.; Yoshida, S.; Ichikawa, J. J. Org. Chem. 2006, 71,
6414.
14. For constructing diphenylmethane, see our former work: (a)
Zhang, S.-T.; Zhang, X.-H.; Ling, X.-G.; He, C.; Huang, R.-F.;
Pan, J.; Li, J. Q.; Xiong, Y. RSC Adv. 2014, 4, 30768. (b) Li Y.;
Xiong, Y.; Li, X.-M.; Ling, X.-G.; Huang, R.-F.; Zhang, X.-H.;
Yang, J.-C. Green Chem. 2014, 16, 2976. (c) Huang, R.-F.;
Zhang, X.-H.; Pan, J.; Li, J.-Q.; Shen, H.; Ling, X.-G.; Xiong, Y.
Tetrahedron 2015, 71, 1540.
15. For the detail of optimization, see supporting information.
16. Hall, D.-M.; Ladbury, J.-E.; Lesslie, M.-S.; Turner, E.-E. J.
Chem. Soc. 1956, 3475.

ACCEPTED MANUSCRIPT
Electronic Supplementary Information
Extension studies on iron(III)-promoted free radical oxidation of
anilines: self-coupling and self-bridged assembling reactions
Jing Pana , Jiaqiang Lia , Ruofeng Huanga , Xiaohui Zhanga , Hang Shena , Yan Xionga, and
Xiangming Zhub
a School of Chemistry and Chemical Engineering, Chongqing University, Chongqing
400044, China.
b
UCD School of Chemistry and Chemical Biology, University College Dublin, Belfield,
Dublin 4, Ireland.
Table of contents
1. Experimental Section........................................................................................................ 2
1.1. General Information............................................................................................... 2
1.2. General Procedure for the oxidative self-coupling reactions.................................... 2
1.3. General Procedure for the oxidative self-bridged assembling reactions................... 2
2. Optimization of reaction conditions .................................................................................. 3
3. General Procedure for the synthesis of 4 ........................................................................... 4
3.1. Preparation of amalgamated zinc............................................................................ 4
3.2. Clemmensen reduction of 2k................................................................................... 4
4. Copies of of 1H- and 13C-NMR .......................................................................................... 5
Corresponding author. Tel.: +86-15086903431; fax: +86-023 65112134; e-mail: xiong@cqu.edu.cn
S1

ACCEPTED MANUSCRIPT
1. Experimental Section
1.1. General Information
1
The H and 13C NMR spectra were recorded in CDCl3 solution at 500/125 MHz
1
spectrometer at 20-25 °C. H NMR chemical shifts were reported in ppm using
tetramethylsilane (TMS, δ = 0.00 ppm) as the internal standard. The data of 1H NMR
was reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t =
triplet, q = quartet, m = multiplet), coupling constant (J values) in Hz and integration.
13C NMR spectra were reported in parts per million using solvent CDCl3 (δ = 77.2
ppm) as an internal standard. All the reagents used were of analytical grade,
purchased locally and used without any purification unless otherwise specified.
Column chromatographys were performed using silica gel, and analytical thin-layer
chromatography (TLC) which was used to monitor the reactions was performed on
silica gel plates.
1.2. General Procedure for the oxidative self-coupling reactions
To a stirred mixture of FeCl3·6H2O (270.3 mg, 1.0 mmol) and 2.0 mL toluene was
added aniline 1 (0.4 mmol) at room temperature. The reaction was stirred at 85 °C for
2 h in atmosphere. After it was cooled to room temperature, the reaction mixture was
quenched by aqueous ammonia solution (mass fraction: 25%-28%, 10 mL) and
extracted with dichloromethane (10 mL per time) until no product was observed in the
extract, monitored by TLC. The organic layer was dried over anhydrous MgSO4,
filtered and concentrated under reduced pressure to give crude product, which was
chromatographed on silica gel column using 1:100 to 1:70 (v/v) EtOAc-petroleum
ether solution as eluent to afford isolated product 2.
1.3. General Procedure for the oxidative self-bridged assembling reactions
To a stirred mixture of aniline 1 (0.4 mmol) and 2.0 mL toluene was added
triethylamine (56 ꢀL, 0.4 mmol) and FeCl3·6H2O (270.3 mg, 1.0 mmol) successively
S2

ACCEPTED MANUSCRIPT
at room temperature. The reaction was stirred at 85 °C for 3.5 h in atmosphere. After
it was cooled to room temperature, the reaction mixture was quenched by aqueous
ammonia solution (mass fraction: 25%-28%, 10 mL) and extracted with
dichloromethane (10 mL per time) until no product was observed in the extract,
monitored by TLC. The organic layer was dried over anhydrous MgSO4, filtered and
concentrated under reduced pressure to give crude product, which was
chromatographed on silica gel column using 1:100 to 1:70 (v/v) EtOAc-petroleum
ether solution as eluent to afford isolated product 3.
2. Optimization of reaction conditions
Table S1. Optimization conditions for the self-bridged assembling reaction of
N,N-dimethylanilinea
Entry
1
Oxidant (eq.)
Additives (eq.) T (°C)
t (h)
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
2.5
3.0
3.5
4.0
3.5
3.5
Yield (%)b
FeCl3 (2.5)
Et3N (1.0)
Et3N (1.0)
Et3N (1.0)
Et3N (1.0)
K2CO3 (1.0)
DIEA (1.0)
NaOH (1.0)
Phen (1.0)
Et3N (1.0)
Et3N (1.0)
Et3N (1.0)
Et3N (0.5)
Et3N (1.5)
Et3N (1.0)
Et3N (1.0)
Et3N (1.0)
Et3N (1.0)
Et3N (1.0)
Et3N (1.0)
85
85
85
85
85
85
85
85
85
85
85
85
85
85
85
85
85
100
120
41
0
2
Fe2(SO4)3 (2.5)
c
3
Fe(NO3)3 (2.5)
-
4
FeCl3·6H2O (2.5)
FeCl3·6H2O (2.5)
FeCl3·6H2O (2.5)
FeCl3·6H2O (2.5)
FeCl3·6H2O (2.5)
FeCl3·6H2O (1.0)
FeCl3·6H2O (2.0)
FeCl3·6H2O (3.0)
FeCl3·6H2O (2.5)
FeCl3·6H2O (2.5)
FeCl3·6H2O (2.5)
FeCl3·6H2O (2.5)
FeCl3·6H2O (2.5)
FeCl3·6H2O (2.5)
FeCl3·6H2O (2.5)
FeCl3·6H2O (2.5)
77
49
76
13
35
31
53
76
62
64
77
83
88
80
87
52
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
a
Reaction conditions: N,N-dimethylaniline (0.4 mmol), iron sources, and additives (specified
S3

ACCEPTED MANUSCRIPT
amounts) in 2.0 mL of toluene. b Isolated yields. c Complex mixture.
3. General Procedure for the synthesis of 4
3.1. Preparation of amalgamated zinc
To a round-bottom flask was added zinc powder (480 mg, 7.3 mmol) and mercuric
chloride (48 mg, 0.2 mmol), followed by H2O (800 µL, 44.4 mmol) and con.
hydrochloric acid (24 µL, 0.8 mmol). The reaction mixture was stirred at room
temperature for 10 min, the solution was decanted, and amalgamated zinc was
obtained.
3.2. Clemmensen reduction of 2k
To freshly prepared amalgamated zinc was added diacetyldiphenyl 2k (65 mg , 0.2
mmol), H2O (280 µL, 15.6 mmol) and con. hydrochloric acid (720 µL, 23.3 mmol)
successively. The resulting mixture was boiled under reflux for 2 h. The reaction
mixture was washed by diethyl ether (5 mL) and the solid residue was removed. The
solution was alkalized by saturated NaHCO3 and extracted by diethyl ether (5 mL×3).
The organic layers were combined, dried over anhydrous Mg2SO4, filtered and
concentrated under reduced pressure to give crude product, which was
chromatographed on silica gel column using EtOAc-petroleum ether (1: 60, v/v)
solutions as eluent to afford white solid 4.
S4

ACCEPTED MANUSCRIPT
4. Copies of of 1H- and 13C-NMR
N4,N4,N4',N4',3,3'-hexamethyl-[1,1'-biphenyl]-4,4'-diamine (2a)
S5

ACCEPTED MANUSCRIPT
N4,N4,N4',N4',2,2'-hexamethyl-[1,1'-biphenyl]-4,4'-diamine (2b)
S6

ACCEPTED MANUSCRIPT
2,2'-diethyl-N4,N4,N4',N4'-tetramethyl-[1,1'-biphenyl]-4,4'-diamine (2c)
S7

ACCEPTED MANUSCRIPT
N4,N4,N4',N4',2,2',6,6'-octamethyl-[1,1'-biphenyl]-4,4'-diamine (2d)
S8

ACCEPTED MANUSCRIPT
5,5'-difluoro-N4,N4,N4',N4',2,2'-hexamethyl-[1,1'-biphenyl]-4,4'-diamine (2e)
S9

ACCEPTED MANUSCRIPT
2,2'-difluoro-N4,N4,N4',N4'-tetramethyl-[1,1'-biphenyl]-4,4'-diamine (2f)
S10

ACCEPTED MANUSCRIPT
2,2'-dichloro-N4,N4,N4',N4'-tetramethyl-[1,1'-biphenyl]-4,4'-diamine (2g)
S11

ACCEPTED MANUSCRIPT
2,2'-dibromo-N4,N4,N4',N4'-tetramethyl-[1,1'-biphenyl]-4,4'-diamine (2h)
S12

ACCEPTED MANUSCRIPT
2,2'-diiodo-N4,N4,N4',N4'-tetramethyl-[1,1'-biphenyl]-4,4'-diamine (2i)
S13

ACCEPTED MANUSCRIPT
dimethyl 4,4'-bis(dimethylamino)-[1,1'-biphenyl]-2,2'-dicarboxylate (2j)
S14

ACCEPTED MANUSCRIPT
1,1'-(4,4'-bis(dimethylamino)-[1,1'-biphenyl]-2,2'-diyl)bis(ethan-1-one) (2k)
S15

ACCEPTED MANUSCRIPT
N4,N4,N4',N4'-tetramethyl-2,2'-dinitro-[1,1'-biphenyl]-4,4'-diamine (2l)
S16

ACCEPTED MANUSCRIPT
4,4'-bis(dimethylamino)-[1,1'-biphenyl]-3,3'-dicarbonitrile (2m)
S17

ACCEPTED MANUSCRIPT
N4,N4,N4',N4'-tetramethyl-[1,1'-binaphthalene]-4,4'-diamine (2n)
S18

ACCEPTED MANUSCRIPT
2,2',5,5'-tetramethoxy-N4,N4'-dimethyl-[1,1'-biphenyl]-4,4'-diamine (2o)
S19

ACCEPTED MANUSCRIPT
N4,N4'-diethyl-3,3'-dimethyl-[1,1'-biphenyl]-4,4'-diamine (2p)
S20

ACCEPTED MANUSCRIPT
2,2'-dichloro-N4,N4'-dimethyl-[1,1'-biphenyl]-4,4'-diamine (2q)
S21