The reaction of red phosphorus with 1-bromonaphthalene in the KOH-DMSO system: Synthesis of tri(1-naphthyl)phosphane

Article abstract of DOI:10.1002/hc.20671

Red phosphorus reacts with 1-bromonaphthalene in the KOH-DMSO system upon heating (47-70°C, 3 h) to give tri(1-naphthyl)phosphane in 10% yield. Microwave activation (600 W, 6 min) of the reaction affords the above-mentioned phosphane in 25% yield.

Full text of DOI:10.1002/hc.20671

Heteroatom Chemistry
Volume 22, Number 2, 2011
The Reaction of Red Phosphorus with
1-Bromonaphthalene in the KOH–DMSO
System: Synthesis of
Tri(1-Naphthyl)phosphane
Vladimir A. Kuimov, Svetlana F. Malysheva, Nina K. Gusarova,
Tamara I. Vakul’skaya, Spartak S. Khutsishvili, and
Boris A. Trofimov
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of
Sciences, 664033 Irkutsk, Russian Federation
Received 8 October 2010; revised 6 December 2010
ticular, phosphanes, phosphane oxides, and phos-
ABSTRACT: Red phosphorus reacts with 1-
phinic acids [1]. For example, alkyl, arylalkyl, allyl
halides [1c] as well as aryl- and hetarylalkenes, and
bromonaphthalene in the KOH–DMSO system
upon heating (47–70◦C,
3
h) to give tri(1-
acetylenes have been employed in this reaction. At
the same time, the attempts to carry out the reaction
of elemental phosphorus with halobenzenes in the
above superbasic systems have failed. Meanwhile,
it was reported on the reaction of red phosphorus
with halobenzenes in alkali metal–liquid ammonia
system, the reaction being considered to proceeding
via the SRN1 mechanism [2]. In the literature, there
are no explicit data on straightforward phosphina-
tion of 1-bromonaphthalene by red phosphorus to
furnish tri(1-naphthyl)phosphane. The latter, being
a sterically hindered tertiary phosphane, was found
be an excellent ligand for metal complex catalysts in-
ducing many types of transformations. This ligand
was employed for the preparation of complexes [3],
showing high catalytic activity in the cross-coupling
reactions [4], synthesis of diaryl ketones [5] and al-
cohols [6], hydrogenation [7], cyclization [8], and re-
duction reaction [9] as well as the complexes having
intense long-lived luminescence and photolumines-
cence [10].
naphthyl)phosphane in 10% yield. Microwave acti-
vation (600 W, 6 min) of the reaction affords the
above-mentioned phosphane in 25% yield. 2011 Wi-
ley Periodicals, Inc. Heteroatom Chem 22:198–203, 2011;
View this article online at wileyonlinelibrary.com. DOI
10.1002/hc.20671
ꢀ
C
INTRODUCTION
One-pot phosphorylation of available electrophiles
with red phosphorus in superbase systems like
KOH–DMSO or under phase-transfer conditions
represents one of the most convenient and promising
approaches to the C P bond formation and synthesis
of important organophosphorus compounds, in par-
Correspondence to: Boris A. Trofimov; e-mail: mal@irioch.irk.ru.
Contract grant sponsor: President of the Russian Federation
(Program for the Support of Young Russian Scientists).
Contract grant number: MK-629–2010.3.
Contract grant sponsor: Russian Foundation for Basic Re-
search.
However, the known syntheses of tri(1-naphthyl)
phosphane are multistep and laborious and require
aggressive and poisonous phosphorus halogenides
Contract grant number: 08-03-00251.
2011 Wiley Periodicals, Inc.
c
ꢀ
198

Reaction of Red Phosphorus with 1-Bromonaphthalene in the KOH–DMSO System 199
SCHEME 1 Synthesis of tri(1-naphthyl)phosphane.
and flammable unstable organometallic reactants
[11]. For example, tri(1-naphthyl)phosphane has
been prepared from 1-bromonaphthalene, metal Li
(or n-BuLi), and phosphorus trichloride in absolute
ethyl ether in 20–30% yield (Scheme 1).
Therefore, the development of a simple straight-
forward approach to the synthesis of tri(1-
naphthyl)phosphane represents a challenging goal.
Interestingly, the ultrasound irradiation (1.5 h,
120–125◦C) of the reaction delivered mainly naph-
thalene (58%), whereas compounds 2 and 4 were
detected only in trace amounts.
A plausible mechanism of phosphination of elec-
trophile 1 can be rationalized as follows (Scheme 3):
The reaction is triggered by the generation of
polyphosphide (A) and polyphosphinite (B) anions
(step 1) from red phosphorus under the action of a
superbase [1c]. Then, the anions A and B interact
with electrophile 1. Eventually, phosphane 2 might
be formed from phosphide anions (step 2), whereas
acid 4 may be produced from polyphosphinite an-
ions (step 3).
However, mechanism shown in Scheme 3 does
not match entirely with the data on hydroquinone
inhibition of the phosphination. Also, it does not al-
low the formation of naphthalene and its derivatives
5 and 6 to be explained. It can be assumed that the
mechanism of the formation of compounds 3,5,6 in-
volves the generation of radical anion C via the elec-
tron transfer from the phosphide anion to bromide
1 (the initiation step) [12,13]. The radical anion C
is unstable (decay rate k1 = 2 × 108 s−l in DMSO
[14]), and its fragmentation affords 1-naphthyl rad-
ical D and bromine anion [15]. The known interac-
tion of radical D with DMSO through the abstraction
of a hydrogen atom from DMSO gives naphthalene
3 and radical DMSO [16]. The latter is coupled with
radical D to form compound 5. The formation of
binaphthalenes 6 results from radical D recombina-
tion (Scheme 4).
RESULTS AND DISCUSSION
Herein, we report a simple and straightforward syn-
thesis of tri(1-naphthyl)phosphane (2) by the direct
phosphination of 1-bromonaphthalene (1) with red
phosphorus. The reaction proceeds in the KOH–
DMSO system in the presence of small quantity of
H2O (as a cocatalyst) at 47–70◦C for 3 h under argon
blanket to give phosphane 2 in 10% yield (Scheme 2).
Apart from the target phosphane, naphthalene (3)
(27%) and phosphonic acid 4 (4%) were detected in
the reaction mixture.
In addition, two isomers of binaphthalene (5, M+
253) and 1-[(methylsulfinyl)methyl]naphthalene (6,
M+ 204) (total yield of compounds 5 and 6 is ∼1%)
were identified in the reaction mixture (MS).
In the presence of hydroquinone, the reaction
was almost stopped: Only acid 4 and naphthalene 3
were formed in 6% and 3% yields, respectively. In the
absence of KOH, red phosphorus did not practically
react with 1-bromonaphthalene.
It is a common knowledge that microwave irra-
diation can be very effective to initiate SRN1 reactions
[12]. The microwave activation (600 W, 6 min) of the
system red phosphorus, 1-bromonaphthalene, KOH,
DMSO, and H2O increased efficacy, chemoselectiv-
ity, and rate (by 30 times) of the reaction to afford
phosphane 2 in 25% yield, the naphthalene being
formed in 26% yield.
Indeed, a signal of naphthalene radical D [17] (g
= 2.0034, ꢀH = 10 G) was registered by the ESR
technique.
The single-electron transfer mechanism of the
reaction studied may also be responsible for the for-
mation of phosphane 2 from phosphorus red and
SCHEME 2 Reaction of red phosphorus with 1-bromonaphthalene.
Heteroatom Chemistry DOI 10.1002/hc

200 Kuimov et al.
SCHEME 3 Plausible mechanism of phosphination of 1-bromonaphthalene.
1-bromonaphthalene. According to [12,13,18], radi-
cal D can react with phosphide anions to yield new
radical anion E.
The most striking feature of the reaction ob-
served is its chemo- and regioselectivity, namely the
formation of tri(1-naphthyl)phosphane only without
retaining the phosphanes 9 and 10 in the reaction
mixture. This is more surprising that the every
next coupling (second and third) of the naph-
thyl radical meets the all-growing steric hindrance.
This phenomenon may result from high stationary
concentration of the naphthyl radicals and easy
dissociation of 1-naphthylphosphane 9 and bi(1-
naphthyl)phosphane 10 to the corresponding an-
ions due to the electron-withdrawing effect of the
napththyl radicals.
The electron transfer from radical anion E to
bromide 1 renders the 1-naphthylphosphane (9) and
the radical anion C, which continues the chain
propagation cycle (Scheme 5). It is known [19]
that 1-bromonaphthalene possesses a higher elec-
tron affinity than the substitution product (in this
case, phosphane 9) that facilitates the removal
of extra electron from its radical anion. Further-
more, compound 9 in the presence of a strong
base gives phosphide anion F. The latter reacts
with radical D followed by the electron transfer to
bromide 1 to furnish the disubstitution product,
bi(1-naphthyl)phosphane 10, which finally affords
(via the same reaction sequence) the trisubstitution
product, tri(1-naphthyl)phosphane 2.
In conclusion, the straightforward reaction
of red phosphorus with 1-bromonaphthalene in
the superbase system KOH–DMSO (including the
microwave-assisted version) has been accomplished
for the first time.
A simple one-pot synthe-
This mechanism is in agreement with the
data obtained for the reaction of halonaphthalenes
with C- [12,20], N- [21], O- [21,22], P- [12,13,18],
S- [14b,15,21,23], and As-centered nucleophiles
[20d,24].
sis of tri(1-naphthyl)phosphane, an excellent lig-
and of growing popularity for metal complex
catalysts inducing many types of transforma-
tions, has been developed on the basis of this
reaction.
SCHEME 4 Ways of byproducts formation.
Heteroatom Chemistry DOI 10.1002/hc

Reaction of Red Phosphorus with 1-Bromonaphthalene in the KOH–DMSO System 201
SCHEME 5 Synthesis of phosphane 2 by radical nucleophilic substitution reaction.
EXPERIMENTAL
was stirred additionally for 30 min. The suspension
was diluted with water (50 mL) and extracted with
toluene (3 × 70 mL). The combined organic extracts
were washed with brine (3 × 20 mL) and evaporated
under reduced pressure. A liquid residue was heated
under 2 Torr (90◦C oil bath), and 1.1 g (yield 27%) of
naphthalene (3) was sublimated. The latter was iden-
All manipulations were carried out in argon atmo-
sphere. IR spectra were measured with a Bruker
IFS 25 instrument in KBr (cm−1). The H, 13C, and
1
31P NMR spectra were measured on a Bruker DPX
400 spectrometer (400.13, 100.61, and 161.98 MHz,
respectively) in CDCl3 or DMSO-d6 solutions and
referenced to internal HMDS (1H), CHCl3 (13C),
and external 85% H3PO4 (31P) standards. The EI
mass spectra were obtained on a Shimadzu GCMS-
QP5050 mass spectrometer. Melting points were ob-
tained with a Stanford Research Systems’ Optimelt
automatic melting-point device without correction.
ESR spectra were recorded on an ELEXSYS spec-
trometer
1
tified by H, 13C NMR, and mass-spectrometry (m/z
128). After removal of 3, the prepared crude product
was allowed to stand for 24 h at 0–5◦C, and precip-
itated crystals were filtered off, washed with ether,
and dried under vacuum to give 0.25 g of phosphane
2. The filtrate was fractionated in vacuum (2 Torr,
125◦C oil bath) to recover 4.9 g (55% conversion)
of unreacted 1 (m/z 206 (M+)). Undistillable waxy
product (0.3 g) was dissolved in 10 mL benzene and
reprecipitated into hexane (30 mL). The precipitate
was filtered off, washed with hexane, and dried un-
der vacuum to give 0.15 g of phosphane 2. Thus, to-
tal yield of phosphane 2 was 0.4 g (10%) (calculated
with conversion 1).
The aqueous layer was acidified with a 35% aq.
HCl up to pH 4–5 (to neutralize 1-NpP(O)(OK)2)
and extracted with chloroform (3 × 20 mL). The
combined chloroform extracts were washed with
brine (3 × 15 mL) and dried over CaCl2. The sol-
vent was removed, and the residue was washed with
hexane (5 × 5 mL). Hexane was removed, and the
residue was dried in vacuum to give 0.2 g (3%) 1-
naphthylphosphonic acid 4.
E-580 (Bruker) instrument was used in a sta-
tionary mode. Microwave irradiation was performed
in multimode modified microwave oven, Samsung
M181DNR, (maximum power level 850 W) equipped
with a reflux condenser. We used open vessel mi-
crowave technology (atmospheric pressure). The re-
action of red phosphorus with styrene was per-
formed in a round-bottom flask (Pyrex). A 500-mL
one-necked flask was placed into the multimode re-
actor (impulse magnetron OM75P(31), power 1.25
MW/2.45 GHz), and was equipped with a reflux con-
denser, which was brought out via a special hole. The
brand red phosphorus of the USSR was employed.
Preparation of Tri(1-naphthyl)phosphane (2)
Method b. Under microwave irradiation, a mix-
ture of red phosphorus (3.1 g, 0.1 mol), 1- bromon-
aphthalene 1 (10.87 g, 0.05 mol), KOH (10 g, 0.18
mol), H2O (4 mL), and DMSO (35 mL) was irradi-
ated (600 W) for 6 min. The reaction mixture was
treated by the above-mentioned protocol (method a)
Method a. A mixture of red phosphorus (3.1
g, 0.1 mol), 1-bromonaphthalene 1 (10.87 g, 0.05
mol), KOH (10 g, 0.18 mol), H2O (4 mL), and DMSO
(40 mL) was stirred at 47–50◦C for 2.5 h. Then tem-
perature was raised up to 70◦C, and the mixture
Heteroatom Chemistry DOI 10.1002/hc

202 Kuimov et al.
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(1.72 g, yield 26%). Conversion of initial bromide 1
was 47%.
Tri(1-naphthyl)phosphane (2). Crystalline pow-
der. mp 280–282◦C (benzene). (lit. [11]) IR (KBr)
(cm−1): 760, 795 δ = CH,C C, 1320, 1380, 1500,
1550, 1585, 1610 vC C, 3040, 3070 v = CH. 1H NMR
(DMSO-d6, 400.13 MHz) δ: 6.81 (dd, 3H, 3-H, 3 J 5.7,
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4 J 5.7), 7.33 (dd, 3H, 2-H, J 7.5, J 7.5), 7.49 and
7.53 (m, 6H, 6,7-H), 7.95 and 7.98 (d, 6H, 4,5-H,
3 J 8.2), 8.36 (ddd, 3H, 8-H, 3 J 8.0, 4 J 4.5, 4 J 0.5);
13C NMR (DMSO-d6, 100.62 MHz) δ: 125.97, 126.26,
3
126.77, 127.76, 128.97, 129.97, 131.96 (d, J 10.7),
3
3
132.89, 133. 31 (d, J 5.0), 135.00 (d, J 23.63); 31P
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1-Naphthylphosphonic acid [1-NpPO(OH)2](4).
Light-yellowish powder. mp 204–206◦C (benzene)
(lit. [26]). IR (KBr) (cm−1): 470 δasCPO, 550 δPO2 670
δ = CC, 750, 780 γ = CH, δ = CH,C C, 830 δasCH, 920,
940 γ OH, 985 vsPO2,PO3, 1110, 1150, 1170, 1200 br
vP O, vasPO2, PO3, 1320, 1350, 1420 δCH,CH2, 1450,
1500, 1550, 1585, 1610 vC C, 1700, 2260, 2520 vOH,
1
2850, 2900, 3040 v = CH. H NMR (CDCl3) δ: 6.35
(m, 2H, OH), 7.30 (m, 1H, 6-H), 7.41–7.35 (m, 1H, 3-
H), 7.50 (m, 1H, 7-H), 7.78 (d, 1H, 5-H), 7.89 (d, 1H,
4-H), 8.16 (dd, 1H, 2-H, J15, 5.8 Hz), 8.50 (d, 1H,
8-H, J 7.8 Hz). 13C NMR (CDCl3) δ: 124.51 (d,
J14.7 Hz), 126.03 (s), 126.62 (d, J3.7 Hz), 127.20
(d, J31.7 Hz), 128.59 (d, J8.8 Hz), 132.66 (d, J10.3
Hz), 132.68 (d, J130.5 Hz), 133.10 (s), 133.13 (d,
J22.8 Hz), 133.50 (d, J9.0 Hz). 31P NMR (CDCl3) δ:
35.5. Anal. Calcd for C10H9O3P: C, 57.70; H, 4.36; P,
14.88. Found: C, 59.07; H, 4.95; P, 14.61.
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