Synthesis and reactivity of pentavalent biphenyl-2,2′-ylenebismuth derivatives

Article abstract of DOI:10.1039/b006307j

Phenylbiphenyl-2,2′-ylenebismuth diacetate reacted with nucleophiles under basic conditions to give modest to good yields of the C-phenylated substrates. Under copper catalysis, it reacted with hydroxy or amino groups to give the products of O- or N-phenylation. In both sets of reaction conditions, this reagent showed a reduced reactivity compared to the analogous triphenylbismuth diacetate reagent. It showed also a high regioselectivity as only the phenyl derivatives were detected and isolated.

Full text of DOI:10.1039/b006307j

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Synthesis and reactivity of pentavalent biphenyl-2,2Ј-ylenebismuth
derivatives
Alexey Yu. Fedorov and Jean-Pierre Finet*
1
Laboratoire “Chimie, Biologie et Radicaux Libres” UMR 6517 CNRS-Universités
d’Aix-Marseille 1 et 3, Faculté des Sciences St Jérôme, case 541, 13397 Marseille Cedex 20,
France
Received (in Cambridge, UK) 2nd August 2000, Accepted 13th September 2000
First published as an Advance Article on the web 30th October 2000
Phenylbiphenyl-2,2Ј-ylenebismuth diacetate reacted with nucleophiles under basic conditions to give modest to
good yields of the C-phenylated substrates. Under copper catalysis, it reacted with hydroxy or amino groups to give
the products of O- or N-phenylation. In both sets of reaction conditions, this reagent showed a reduced reactivity
compared to the analogous triphenylbismuth diacetate reagent. It showed also a high regioselectivity as only the
phenyl derivatives were detected and isolated.
appeared to be moderately stable.7 The heterocyclic 10,10-
Introduction
dichloro-10-(4Ј-methylphenyl)-10λ5-phenothiabismine
5,5-
The uniqueness of organobismuth compounds as selective
reagents in organic chemistry is becoming more widely recog-
nized. A large part of their chemistry involves arylbismuth
derivatives, which behave either as oxidizing agents or as aryl-
ating reagents towards a number of nucleophilic substrates.1,2
The chemoselectivity is strongly dependent upon the choice of
the bismuth ligands and of the reaction conditions. With tri-
arylbismuth diacetates 1, selective C-, N- or O-arylation can be
dioxide 3 is a relatively stable substance, which upon treatment
with the sodium salt of dibenzoylmethane resulted only in the
transfer of the tolyl group, leading to the formation of 1,3-
diphenyl-2-tolylpropane-1,3-dione (76%).
As part of our studies on the concept of ligand coupling in
heteroaromatic compounds,8 we decided to investigate the
chemistry of pentacoordinate biphenylylbismuth derivatives
and in particular the diacetate, as triarylbismuth diacetates can
perform the various types of aryl transfer reactions.3 We now
report the synthesis of (biphenyl-2,2Ј-ylene)phenylbismuth
diacetate 5 and its reactions with various types of nucleophilic
substrates both under basic conditions and under copper
catalysis.
Results and discussion
Biphenyl-2,2Ј-ylenephenylbismuthane 4 was prepared by a
modification of the method of Wittig and Hellwinkel.9 The
TMEDA-adduct of 2,2Ј-dilithiobiphenyl (TMEDA = N,N,NЈ,
NЈ-tetramethylethylenediamine)10 was first isolated and then
treated with phenylbismuth diiodide to afford the phenyl-
bismuthane 4. The diacetate 5 was then easily obtained by
treatment of 4 with sodium perborate in acetic acid.11 Under
these mild conditions, the diacetate 5 was isolated in a good
yield (69%) (Scheme 1).
performed under three different sets of reaction conditions:3 a)
C- and O-arylation via a covalent intermediate; b) O-arylation
under neutral conditions; c) O- and N-arylation under copper
catalysis. However, these reagents require the use of three aryl
groups of which only one aryl group is eventually transferred.
When the transfer of a highly functionalized aryl group is
desired, one possibility of avoiding the loss of two aryl groups
would be to use an unsymmetrical triarylbismuth derivative.
However, although a limited number of studies have shown the
difference in ligand transfer ability in the case of unsymmetrical
triarylbismuth derivatives, a selective transfer cannot be real-
ized with such a system.4,5 An alternative structure to avoid the
loss of two ligands would be to use a stabilized form of these
two ligands, which would lead to the selective transfer of the
third aryl group. One such possibility is to include these
two aryl groups in a heterocyclic bismuth substructure. Few
structures of this type have been prepared and their reactivity
has been barely explored. In 1968, Hellwinkel and Bach syn-
thesised the pentacoordinate biphenyl-2,2Ј-ylenetriphenyl-λ5-
bismuthane 2.6 More recently, Suzuki et al. reported the
synthesis of various dibenzo[b,e]bismine compounds which
Scheme 1 Reagents and conditions: i, BuLi, TMEDA, 50 ЊC, 1.5 h;
ii, PhBiI2, THF–ether, RT; iii NaBO3, AcOH, RT, 1 h.
The reactions of the cyclic reagent 5 with different nucleo-
philes under basic conditions were performed in THF using
TMG (N,N,NЈ,NЈ-tetramethylguanidine) as the base (Table 1).
DOI: 10.1039/b006307j
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This journal is © The Royal Society of Chemistry 2000
3775

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Table 1 Phenylation reactions with 5 under basic conditionsa
Substrate
Reaction conditions
Products (%)
6
8
TMG, 24 h, RT
TMG, 48 h, RT
TMG, 17 h, RT
TMG, 24 h, RT
TMG, 18 h, RT and 1 h, 50 ЊC
TMG, CH2Cl2, 1 h, RT and 15 h reflux
t-BuOK, 15 h, 50 ЊC
TMG, 96 h, RT
t-BuOK, 24 h, RT and 24 h, 50 ЊC
7 (79); 6 (14); 4 (19)
9 (6); 8 (84); 4 (16)
11 (95); 4 (14)
10
12
14
16
16
19
19
13 (61); 4 (34)
15 (53); 4 (45)
No reaction
18 (14); 17 (18); 16 (60)
No reaction
No reaction
a All reactions were performed in THF unless otherwise stated.
Table 2 Copper-catalysed phenylation reactions with 5a
Substrate
Reaction conditions
Product (%)
8
20
22
24
26
28
30
24 h, RT and 24 h, 50 ЊC
48 h, 50 ЊC
14 h, RT
14 h, 50 ЊC
20 h, 50 ЊC
3 h, 50 ЊC
15 h, 50 ЊC
No reaction
21 (88); 20 (10); 1 (85)
23 (80); 4 (26)
25 (64)
27 (18)
29 (96)
31 (78)
a All reactions were performed in THF in the presence of copper diac-
etate (0.1 equiv.).
bismuth atom into a five membered ring in the biphenyl-2,2Ј-
ylenebismuthane leads to a decrease of the reaction rates simi-
lar to the effect of the introduction of an ortho-methyl group
on the aryl ligand.12 Moreover, only the ligand coupling
product between the substrate and the phenyl substituent has
been observed. This is in contrast with the reaction of aryl-
biphenylylsulfonium13 or selenonium14 salts with nucleophiles,
which led to mixtures of different ligand coupling products. In
this case, tetracoordinate sulfuranes were formed and no
significant difference existed between the three aryl–sulfur
bonds that could induce selectivity in the ligand coupling
process. However, in the case of the trigonal bipyramidal struc-
ture of the pentacoordinate bismuth system, the biphenylyl
group is blocked in the unfavourable apical plane, as one phenyl
of the biphenylyl group forms an equatorial bond to bismuth
and the second one lies in the apical position. During the ligand
coupling step, the third phenyl group can lie in the equatorial
plane, adopting an ideal conformation for the interaction
between the two π-systems of the substrate and of the phenyl
group (Scheme 2). Thus, this results in the selective coupling of
the substrate with the equatorial phenyl ligand.
The reactions of the cyclic reagent 5 with different O- and
N-nucleophiles under copper catalysis conditions were per-
formed in THF using copper() diacetate as the catalyst
(Table 2). In the case of the O-arylation reaction, the cyclic
compound 5 was treated with the phenol 8 and the 1,3-diol 20.
The reactivity of 5 appeared again to be significantly reduced
by comparison with triphenylbismuth diacetate. Indeed, the
copper-catalysed reaction of triphenylbismuth diacetate with
the phenol 8 as well as with the 1,3-diol 20 led to high yields
of the O-phenyl derivatives. By contrast, the cyclic biphenylyl
derivative 5 reacted only with the glycol 20 to afford a good
yield of the mono-O-phenyl derivative 21. This reduced reactiv-
ity was also observed in the case of the N-phenylation reaction.
In this case, good yields of the N-phenylation products were
only obtained when the reaction was performed at 50 ЊC. Even,
tert-butylamine 26 gave the N-phenyl product 27, however in a
rather modest yield (18%). It must be noted that the reaction of
5 with the primary amine 24 afforded only the monophenylated
product, when triphenylbismuth diacetate gave a mixture of the
mono- and di-phenyl derivatives.
With all the substrates (phenols 6 and 8, β-dicarbonyl com-
pounds 10 and 12, nitroalkanes 14 and enolized ketones 16), the
reactions appeared to be slower than the similar reactions
performed with the corresponding triarylbismuth diacetate
derivatives. This reduced reactivity resulted in longer reaction
times and/or in lower overall yields. For example, in the case of
the phenolic substrates, the very reactive β-naphthol 6 gave a
good yield of 1-phenyl-2-naphthol (79%). However, the more
sterically hindered 3,5-di-tert-butylphenol 8 gave only a very
poor yield of the monophenyl derivative 9 (6%). In the case of
substrates prone to polyarylation, the behaviour appeared to be
substrate-dependent. Indeed, in the case of the 1,3-diketone 12,
the product of monophenylation 13 was obtained in a relatively
good yield (61%). In the case of the arylketone 16, no reaction
took place when TMG was used as a base. However, in the
presence of the stronger potassium tert-butoxide, a reaction
occurred but led to a poor yield of the mono- and di-phenylated
derivatives, 17 (18%) and 18 (14%) respectively. The cyclo-
hexanone 19 did not lead to any α-arylketone with either
TMG or t-BuOK as the base. It must be noted that in all
cases, the biphenylylbismuth by-product was neither isolated
nor detected. The only isolated by-product was the reduction
product, the phenylbismuthane 4.
The restricted flexibility induced by the insertion of the
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Scheme 2 Mechanism of the ligand coupling step.
solvents under reduced pressure afforded a crude product
which was crystallized from dichloromethane–pentane to give
4 (3.7 g, 56%), mp 166 ЊC, lit.9 167–168 ЊC.
Phenylbiphenyl-2,2Ј-ylenebismuth diacetate (5). A mixture of
sodium perborate monohydrate (0.6 g) and phenylbiphenyl-
2,2Ј-ylenebismuthane (0.9 g) in acetic acid (20 cm3) was stirred
at room temperature for 1 h. The resulting solution was poured
into water (40 cm3) and the mixture was extracted with CH2Cl2
(3 × 20 cm3). The organic extracts were combined, washed with
water, dried over MgSO4. The solvent was distilled under
reduced pressure to a small volume. A mixture of diethyl ether–
pentane (1:3) was added and the solution was kept overnight at
Ϫ15 ЊC to afford 5 as a colorless powder (0.77 g, 69%), mp
183 ЊC; δH (CDCl3, 200 MHz) 1.80 (6H, s, Me), 7.50–7.75 (7H,
m, Ar-H) and 8.10–8.25 (6H, m, Ar-H); δC 20.8 (Me), 124.8,
130.8, 131.0, 131.2, 131.3, 131.9, 132.6, 137.5, 155.8 (C-Ar) and
180.2 (MeCO) (Found: C, 47.55; H, 3.47. C22H19BiO4 requires:
C, 47.49; H, 3.44%).
Arylation reactions with phenylbiphenyl-2,2Ј-ylenebismuth
diacetate in the presence of N,N,NЈ,NЈ-tetramethylguanidine
(TMG)
General procedure. A mixture of the substrate (0.25–0.5
mmol, 1 equiv.) and TMG (1.2 equiv.) in distilled THF (5 cm3
mmolϪ1 of substrate) was stirred for 10 min at room temper-
ature. Phenylbiphenyl-2,2Ј-ylenebismuth diacetate (1.2 equiv.)
was added and the mixture stirred for the time indicated below.
The solvent was distilled off and the residue was purified by
chromatography as described below to afford the reaction
products identical with authentic samples, unless otherwise
stated.
In conclusion, insertion of two phenyl groups of triphenyl-
bismuth into a cyclic system allows the selective transfer of only
the free phenyl group both in base-catalysed C-phenylation and
in the copper-catalysed O- and N-phenylation reactions. The
lower reactivity may be of interest as monophenylation of
β-dicarbonyl compounds was obtained when a mixture of
mono- and di-phenyl products was formed in the reaction with
triphenylbismuth derivatives.
1-Phenyl-2-naphthol (7).15 24 h; CC (pentane–ether 7:3);
colourless plates, mp 84 ЊC; 79%.
Experimental
Melting points were taken on a Büchi capillary apparatus and
are uncorrected. NMR spectra were obtained on a Bruker
3,5-Di-tert-butyl-2-phenylphenol (9).15 48 h; CC (pentane–
ether 97:3) and PLC (pentane–ether 19:1); colourless plates,
mp 71 ЊC (pentane); 6%.
1
AC200 spectrometer: H-NMR at 200.13 MHz and 13C-NMR
at 50.32 MHz. Chemical shifts (δ) are reported in ppm for a
solution of the compound in CDCl3 with internal Me4Si and
J values in hertz. TMEDA refers to N,N,NЈ,NЈ-tetramethyl-
ethylenediamine, TMG refers to N,N,NЈ,NЈ-tetramethyl-
guanidine and ether refers to diethyl ether. CC refers to column
chromatography on silica gel and PLC refers to preparative
layer chromatography.
Ethyl 1-phenyl-2-oxocyclohexanecarboxylate (11).16 17 h; CC
(pentane–ether 7:3); colourless oil; 95%.
3-Phenylpentane-2,4-dione (13).16 24 h; CC (pentane–ether
4:1); colourless oil; 61%.
Preparation of phenylbiphenyl-2,2Ј-ylenebismuth diacetate
Ethyl 2-phenyl-2-nitropropionate (15).17 18 h at room tem-
perature and 1 h at 50 ЊC; CC (pentane–ether); pale yellow oil;
53%.
Phenylbiphenyl-2,2Ј-ylenebismuthane (4). A solution of 2,2Ј-
dilithiobiphenyl–TMEDA10 (4.8 g) in a mixture of anhydrous
THF (50 cm3) and anhydrous ether (70 cm3) was added to
phenylbismuth diiodide (8.1 g). The mixture was stirred for
2.5 hours at room temperature. After addition of water
and extraction of the aqueous phase with dichloromethane,
the organic phase was dried over MgSO4. Distillation of the
Reaction of 6-methoxy-3,4-dihydronaphthalen-1(2H)-one with
phenylbiphenyl-2,2Ј-ylenebismuth diacetate.
A mixture of
6-methoxy-3,4-dihydronaphthalen-1(2H)-one (0.05 g, 1 equiv.),
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potassium tert-butoxide (0.04 g, 1.2 equiv.) and phenyl-
biphenyl-2,2Ј-ylenebismuth diacetate (0.19 g, 1.2 equiv.) in dis-
tilled THF (15 cm3) was stirred for 15 hours at 50 ЊC. Aqueous
work-up followed by column chromatography of the residue
(pentane–ether 3:1) afforded 6-methoxy-2,2-diphenyl-3,4-di-
hydronaphthalen-1(2H)-one 18 (0.013 g, 14%), mp 110 ЊC; δH
(CDCl3, 200 MHz) 2.75–2.95 (4H, m, H-3 and H-4), 3.80 (3H,
s, MeO), 6.56 (1H, d, JH5–H7 2.5, H-5), 7.84 (1H, dd, JH7–H5 2.4,
JH7–H8 8.8, H-7), 7.10–7.37 (10H, m, Ar-H) and 8.14 (1H, d,
JH8–H7 8.8, H-8); δC 26.7 (C-4), 35.1 (C-3), 55.2 (MeO), 59.5
(C-2), 111.9 and 113.3 (C-5 and C-7), 126.5, 126.6, 131.9, 127.9,
128.4, 130.7, 142.2 and 145.6 (C-Ar), 163.3 (C-6) and 197.4
(C-1) (Found: C, 83.79; H, 6.21. C23H20O2 requires: C, 84.12;
H, 6.14%). 6-Methoxy-2-phenyl-3,4-dihydronaphthalen-1(2H)-
one 17 (0.013 g, 18%) obtained as colourless plates, mp 112–
113 ЊC (pentane-ether), lit.18 112–114 ЊC and unreacted starting
material 16 (0.03 g, 60%) were also isolated.
Acknowledgements
Alexey Fedorov thanks the Ministère Français de l’Education
Nationale, de l’Enseignement Supérieur et de la Recherche for
the award of a PECO-NEI post-doctoral fellowship.
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General procedure. A mixture of the substrate (1 equiv.),
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bismuth diacetate (1.1 equiv.) in THF (5 cm3 mmolϪ1 of sub-
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N-(3,4-Dimethylphenyl)-N-phenylamine (23). 14 h at 50 ЊC;
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N-Phenyl-1,2,3,4-tetrahydroisoquinoline (31). 15 h at 50 ЊC;
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3778
J. Chem. Soc., Perkin Trans. 1, 2000, 3775–3778