π-Insertion Reactions of Benzynes into P=N and P=S Double Bonds

Article abstract of DOI:10.1002/ejoc.201301481

The π-insertion reactions of in situ generated benzynes into the P=N bonds of N-benzyl and N-aryl iminophosphoranes and the P=S bonds of phosphane sulfides have been examined by using the Kobayashi benzyne precursors, (2-trimethylsilyl)phenyl triflates. The reactions with iminophosphoranes afforded (2-aminophenyl)phosphonium triflates under mild conditions, most probably by a [2+2]/retro [2+2] cycloaddition sequence and further N-protonation by the solvent (CH₃CN) or N-phenylation by a second molecule of benzyne. The final products of the analogous reactions with P-OCH₃-substituted iminophosphoranes were the respective (2-aminophenyl)phosphane oxides, as result of a final O-demethylation event of the putative phosphonium triflate. The reactions with phosphane sulfides involve a final S-phenylation step to yield (2-phenylthio)phenylphosphonium salts. P-Phenylphosphonium triflates functionalized at the ortho position by amino or thio units were obtained by π-insertion of benzyne into the P=N bond of an iminophosphorane or the P=S bond of a phosphane sulfide.

Full text of DOI:10.1002/ejoc.201301481

FULL PAPER
DOI: 10.1002/ejoc.201301481
π-Insertion Reactions of Benzynes into P=N and P=S Double Bonds
Carmen Lopez-Leonardo,*[a] Rosalia Raja,[a] Fernando López-Ortiz,*[b]
Miguel Ángel del Águila-Sánchez,[b] and Mateo Alajarin*[a]
Keywords: Arynes / Cycloaddition / Insertion / Phosphanes / Iminophosphoranes
The π-insertion reactions of in situ generated benzynes into
the P=N bonds of N-benzyl and N-aryl iminophosphoranes
and the P=S bonds of phosphane sulfides have been exam-
ined by using the Kobayashi benzyne precursors, (2-trimeth-
ylsilyl)phenyl triflates. The reactions with iminophos-
phoranes afforded (2-aminophenyl)phosphonium triflates
under mild conditions, most probably by a [2+2]/retro [2+2]
cycloaddition sequence and further N-protonation by the sol-
vent (CH3CN) or N-phenylation by a second molecule of
benzyne. The final products of the analogous reactions with
P-OCH3-substituted iminophosphoranes were the respective
(2-aminophenyl)phosphane oxides, as result of a final O-de-
methylation event of the putative phosphonium triflate. The
reactions with phosphane sulfides involve a final S-phen-
ylation step to yield (2-phenylthio)phenylphosphonium salts.
gents. This global sequence of reactions most often results
in a tandem strategy for the facile construction of a wide
range of benzofused heterocycles.
Introduction
The reactions of the highly reactive arynes have been ex-
tensively developed as powerful tools in organic synthesis.[1]
The innovation of fluoride-induced in situ generation of
arynes from (2-trialkylsilyl)aryl triflates under mild condi-
tions[2] has naturally resulted in rapid progress in aryne
chemistry during recent years. The [2+2] cycloadditions of
arynes, also considered as π-insertions of arynes into
double bonds, initially provide highly strained benzannul-
ated four-membered rings. The reactions between arynes
and alkenes afford stable benzocyclobutenes.[3] Cycload-
ditions between arynes and compounds containing carbon–
heteroatom double bonds have been far less widely studied
and are still challenging. In this context, several publica-
tions reported the insertion of arynes into the C=O double
bonds of aldehydes,[4] ketones,[5] and amides,[6] as well as
into the C=S bonds of thiones and thioureas,[7] the C=Se
bonds of selones,[8] the C=N bonds of imines,[9] and the
C=P bonds of alkylidenephosphoranes.[10] As a conse-
quence of their considerable ring strain, the adducts of
these reactions tend to undergo a further ring-opening
event to afford ortho-heteroxylylene reactive intermediates
(Scheme 1), which can then be trapped by subsequent rea-
Scheme 1. General π-insertion reaction of benzyne into C=X
double bonds.
In the context of our interest in the chemistry of imino-
phosphoranes[11] and their P-vinyl derivatives,[12] we have
recently reported that the reaction of benzynes with P-alk-
enyl-N-aryl iminophosphoranes yielded the respective 1,4-
benzazaphosphorinium triflates.[13] We rationalized these
conversions by a mechanistic sequence in which the first
step is a π-insertion of benzyne into the P=N bond of the
iminophosphorane, followed by a retro [2+2] cycloaddition/
6π-electrocyclization/protonation cascade (Scheme 2).
[a] Departamento de Química Orgánica, Facultad de Química,
Universidad de Murcia, Regional Campus of International
Excellence “Campus Mare Nostrum”, Espinardo,
30100 Murcia, Spain
E-mail: melill@um.es
http://www.um.es/web/quimica
[b] Área de Química Orgánica, Universidad de Almería,
Carretera de Sacramento s/n, 04120 Almería, Spain
E-mail: flortiz@ual.es
Scheme 2. Mechanistic explanation of the reaction between
benzynes and P,P-alkenyl-substituted iminophosphoranes to yield
1,4-benzazaphosphorinium triflates.
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201301481.
1084
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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π-Insertion Reactions of Benzynes into P=N and P=S Double Bonds
To the best of our knowledge, this was the first report of
a π-insertion reaction of benzyne into a heteroatom–hetero-
atom double bond. In view of those results, we considered
it worthwhile to examine the feasibility of the reaction be-
tween benzynes and the P=N bonds of more simple imino-
phosphoranes and to extend the study of this reactivity to
the P=S moieties of phosphane sulfides. The process proved
to be of broad scope and leads to the formation of a range
of organophosphorus compounds decorated with ortho-
amino and ortho-phenylthio groups in high yields under
very mild reaction conditions.
Scheme 3. Reaction of benzynes with iminophosphoranes to give
(2-aminoaryl)phosphonium triflates.
The reactions with the P,P,P-triphenyl iminophos-
phoranes provided exclusively the (2-aminophenyl)phos-
phonium triflates 3a–3c in good yields (Table 1, Entries 1–
3). However, the standard reaction conditions were not ade-
quate for P-methyl-P,P-diphenyl iminophosphoranes 1d
and 1e and resulted in complex mixtures in which 4 and the
Results and Discussion
To test the feasibility of our proposal, we first prepared starting material were present. As 4 are derivatives of 3, we
a series of iminophosphoranes 1 by the stoichiometric reac- tried to direct the process towards the formation of 4. Thus,
tion of azides and phosphanes under the standard condi- when 2.6 equiv. of benzyne precursor were used, the respec-
tions of the Staudinger imination reaction.[14] In this way, tive (2-phenylamino)phenyl phosphonium triflates 4a and
the starting materials 1 were obtained in good yields (90– 4b were isolated in high yields (Table 1, Entries 4 and 5). In
1
96%) and high purity (Ͼ95% by H and 31P NMR analy- general, the reactions of P,P-dimethyl-P-phenyl iminophos-
sis) and were used successfully in the following reactions phoranes 1f–1j with benzyne precursor 2a (Table 1, En-
without further purification. The treatment of the imino- tries 6–12) gave similar results. Thus, with 1.3 equiv. of 2a,
phosphoranes 1 with either the commercially available mixtures of 3 and 4 were obtained, except in the case of the
benzyne precursor 2-(trimethylsilyl)phenyl triflate (2a) or sterically shielded N-(2,6-dimethylphenyl) derivative
the easily prepared 3-methoxy analog 2b[2b,2c] in the pres- (Table 1, Entry 8), which exclusively yielded 3f. In contrast,
ence of CsF with acetonitrile as solvent gave rise to the the utilization of 2.6 equiv. of 2a gave rise to the respective
phosphonium triflates 3 and/or 4 (Scheme 3, Table 1). Com- N-phenylated compounds 4. The utilization of the unsym-
pounds 4 result from the incorporation of a second equiva- metrical 3-methoxybenzyne [generated in situ from 3-meth-
lent of benzyne at the nitrogen atom of the phosphonium oxy-2-(trimethylsilyl)phenyl triflate] resulted in regioselec-
triflates 3. After extensive optimization experiments with tive reactions, which led to the exclusive formation of the
iminophosphoranes 1b and 1c, the best reaction conditions 3g and 3h regioisomers (Table 1, Entries 13 and 14). Similar
to obtain 3 were established as those in which the 1/benzyne regioselectivities are well known in the use of this and other
precursor/CsF ratio is 1:1.3:3 with a reaction time of 10 h alkoxy-substituted benzynes and are rationalized in terms
in acetonitrile at 10 °C. Attempts to improve the product of electronic and steric factors in the initial step of compar-
yields by using 1,4 dioxane or a toluene/acetonitrile (4:1) able stepwise reactions, which determine the more favorable
mixture as solvent or the KF/18-crown-6 system as a fluo- attack at the meta position of the alkoxy substituent.[15]
ride source failed. The utilization of 2.6 equiv. of benzyne
A careful scrutiny of the analytical and spectroscopic
precursor 2 afforded phosphonium triflates 4 as the main data allowed the unambiguous structural assignment of the
reaction products (Table 1).
phosphonium triflates 3 (see Exp. Sect.). The dissociation
Table 1. Phosphonium triflates 3 and 4.
Entry
1
R1
R2
R3
R4
2
R5
Equiv. 2
Yield of 3 [%][a] Yield of 4 [%][a]
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
1g
1h
1f
1g
1i
1j
1g
1h
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
C6H5
C6H5
C6H5
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
C6H5CH2
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
2b
2b
H
H
H
H
H
H
H
H
H
H
H
H
OCH3
OCH3
1.3
1.3
1.3
2.6
2.6
1.3
1.3
1.3
2.6
2.6
2.6
2.6
1.3
1.3
3a, 70
3b, 56
3c, 65
–
–
–
–
4-CH3C6H4
4-CH3OC6H4
4-CH3OC6H4
4-BrC6H4
4-CH3C6H4
4-CH3OC6H4
2,6-(CH3)2C6H3
4-CH3C6H4
4-CH3OC6H4
4-BrC6H4
4a, 74
4b, 87
–
–
–
4c, 65
4d, 72
4e, 76
4f, 69
–
–
3d, 54[b]
3e, 56[b]
3f, 75
–
9
10
11
12
13
14
–
–
–
4-NO2C6H4
4-CH3OC6H4
2,6-(CH3)2C6H3
3g, 72
3h, 48
–
[a] Yields of isolated products. [b] Compounds 4 were also detected (Ͻ10%).
Eur. J. Org. Chem. 2014, 1084–1095
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C. Lopez-Leonardo, F. López-Ortiz, M. Alajarin et al.
FULL PAPER
Table 2. Selected 13C{1H} NMR spectroscopic data of phosphonium triflates 3 in CDCl3 (298 K). The spectra were measured at 100 or
75 MHz. Chemical shifts (δ) are given in ppm, and coupling constants (J) are in Hz.
δC-1 (1JP,C
)
δC-2 (2JP,C
)
δC-3 (3JP,C
)
δC-4 (4JP,C
)
δC-5 (3JP,C
)
δC-6 (2JP,C
)
3a
3b
3c
3d
3e
3f
97.51 (91.4)
104.97 (91.7)
102.76 (91.7)
115.27 (91.0)
113.26 (90.7)
102.78 (88.6)
97.79 (93.0)
92.19 (92.5)
151.09 (5.1)
149.54 (4.4)
150.47 (4.5)
149.03 (4.4)
149.82 (4.4)
149.05 (4.5)
152.13
113.92 (7.9)
120.80 (7.7)
119.23 (7.5)
126.58 (7.5)
125.00 (7.6)
115.91 (7.6)
105.08 (4.6)
103.38 (6.1)
137.79
137.45
137.44
136.47 (2.1)
136.46 (1.6)
136.98 (2.2)
137.00
118.93 (13.2)
123.04 (12.9)
122.01 (13.0)
125.57 (12.8)
124.67 (12.9)
121.25 (12.6)
115.87 (6.7)
110.59 (7.8)
136.02 (10.5)
136.05 (10.5)
135.94 (10.4)
133.80 (10.3)
133.71 (10.1)
133.64 (9.5)
163.15
3g
3h
152.30 (2.4)
137.39
163.63
of the P=N bond of 1 and the incorporation of its two
termini into the adjacent carbon atoms of the benzyne unit
to give the salts 3 is evidenced by the following key NMR
spectroscopic data. First, the ortho-disubstituted pattern of
1
the new benzene ring is present in their H NMR spectra.
Second, the phosphorus atom is coupled to all of the car-
bon atoms of that ring in their 13C{1H} NMR spectra (see
Table 2), and there is no 31P–13C coupling for the ortho-
and NCipso carbon atoms of the N-aryl ring, which was
present in 1. Moreover, the NH proton is clearly appreciable
1
in the H NMR spectra of 3, whereas the singlet at δ ≈
18 ppm in their 31P{1H} NMR spectra is typical of phos-
phonium salts and is remarkably deshielded with respect
to those of the starting iminophosphoranes 1 (Δδ = 7.00–
20.94 ppm). Finally, the triflate anion is clearly revealed in
their 13C{1H} and 19F{1H} NMR spectra. For instance, the
signals of the respective carbon and fluorine atoms of the
anionic moiety of 3h appear at δC = 120.73 ppm (q, 1JF,C
320.3 Hz) and δF = –78.22 ppm.
=
Compounds 4 were characterized by examination of their
HRMS and NMR spectroscopic data, which are in some
aspects comparable with those of the analogous triflates 3.
The formation of products 3 and 4 is reasonably ex-
plained by a mechanism analogous to that reported for the
Scheme 4. Proposed mechanism for the formation of phosphonium
triflates 3 and 4.
reaction of iminophosphoranes with acetylenic esters[16] class represents a significant improvement as the insertion
and propargylic phosphonium salts (Scheme 4).[17] First, reaction occurs under mild reaction conditions with readily
the iminophosphorane 1 reacts with the in situ generated accessible reagents that are compatible with a variety of
benzyne to yield the formal [2+2] cycloadduct, which then functional groups.
undergoes a retro [2+2] cycloaddition. The resulting ortho-
To gain insight into the structure of species 5 (Scheme 4)
phosphazaxylylene 5 (or its amidophosphonium betaine ca- formed in the insertion of benzyne into the P=N linkage of
nonical form 5Ј) intermediate could act either as a base to iminophosphoranes 1, we undertook a variable-temperature
abstract a proton from the acetonitrile[7c,18] solvent to give multinuclear magnetic resonance study of the deproton-
3 or as a nucleophile with a second equivalent of benzyne ation of phosphonium triflate 3f with 1.1 equiv. of nBuLi
to give 4.
in [D8]THF as solvent. The analysis of the 1H, 7Li, 13C, and
The (2-aminophenyl)phosphonium salts 3 and 4 can be 31P NMR spectra of a 0.1 m sample in the temperature
envisaged as precursors of the corresponding (2-amino- range –30 to –120 °C showed the existence of the neutral
phenyl)phosphanes by reduction with sodium naphthalen- compound 5f [δP(–30 °C) = 11.09 ppm, Scheme 5] in solu-
ide.[19] (ortho-Amino)phosphanes are important hemilabile tion. Although the Li NMR spectrum of the freshly pre-
7
P,N-ligands in transition-metal catalysis and are commonly pared sample measured at –110 °C consisted of four signals
prepared through multistep syntheses.[20] The one-pot pro- at δLi = 0.41, 1.23, 1.35, 1.40 ppm plus that of the LiBr
cedure reported here for the preparation of this compound present in the organolithium base solution used (δLi
=
1086
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π-Insertion Reactions of Benzynes into P=N and P=S Double Bonds
–0.25 ppm), these signals disappear upon standing of the methyl phosphite (for 1m) and aryl azides.[24] Their reac-
sample at low temperature owing to crystallization (Figure tions with 2 were conducted in acetonitrile at room tem-
S46). This crystallization has no effect on the other spectra, perature for 24 h in an optimized 1/2/CsF ratio of 1:1.3:3 to
except for the large intensity decrease of the quartet arising afford the respective 2-(arylamino)phenylphosphane oxides
from the triflate anion in the 13C NMR spectrum (Figure 6a–6c (Scheme 6; Table 3, Entries 1–3) or the phosphonate
S48; δC = 120.56 ppm, 1JF,C = 319.4 Hz). The dearomatized 6d (Scheme 6; Table 3, Entry 4).
phosphorus ylide structure of 5f was identified from the
1
standard combination of 1D [1H, H(31P), 13C, DEPT135,
31P] and 2D [COSY45, heteronuclear multiple quantum co-
herence (HMQC), HMBC, ROESY] NMR spectroscopy at
–30 °C (see Supporting Information).
Scheme 6. Reaction of benzynes with P-methoxy derivatives to give
phosphane oxides.
Table 3. (2-Arylamino)phenylphosphane oxides 6a–6c and phos-
phonate 6d.
Entry
1
R1 = R2 R4
2
R5
Yield of 6 [%]
1
2
3
4
1k
1l
1l
C6H5
C6H5
C6H5
4-CH3C6H4 2a
H
H
6a, 90
6b, 86
6c, 42
6d, 45
4-BrC6H4
4-BrC6H4
2a
Scheme 5. Formation of 5f by deprotonation of 3f and numbering
scheme used. The arrows indicate the NOEs observed in the 2D
ROESY spectrum (mixing time 200 ms, 30 °C).
2b OCH3
1m OCH3
4-CH3C6H4 2a
H
1
The H and 31P NMR spectra of 5f are temperature-de-
The analytical and spectroscopic data of 6 were consis-
pendent. The 31P NMR signal broadens in the temperature tent with their structures. Their 1H and 13C{1H} NMR
range 30 to –80 °C, coalesces at –90 °C, and splits into two spectra showed the absence of one methoxy group from the
signals at lower temperature (Figure S44). At –120 °C, two respective P-methoxy iminophosphorane precursor. Their
relatively narrow signals (W1/2 Ͻ 25 Hz) are observed at δP 31P{1H} NMR spectra show a singlet in the δ = 36.23–
1
= 11.51 and 17.88 ppm in a ratio of 65:35. The H NMR 38.75 ppm interval for 6a–6c and at δ = 24.45 ppm for 6d.
spectra showed similar features. At –120 °C, the signals in
The formation of phosphane oxides 6 most probably oc-
the aromatic region and those of the C–Me groups appear curs via the corresponding (2-arylamino)phenylphosphon-
almost duplicated (ratio of 65:35 from integration of the 5- ium triflate of structure similar to that of 3. A subsequent
H peak) owing to the presence of two species (Figure S43). cleavage of the O–CH3 bond in an Arbuzov-like manner
Most importantly, at this temperature, the P–Me protons finally leads to the respective phosphane oxides 6a–6c (R1
generate two equally intense doublets at δH = 2.58 (2JP,H
=
= R2 = C6H5) or dimethyl phosphonate 6d (R1 = R2
=
13.4 Hz) and 2.64 ppm (2JP,H = 14.6 Hz). These doublets OCH3). This latter transformation is quite usual in the
1
collapse into two singlets in the H{31P} spectrum (Figure chemistry of P-alkoxyphosphonium salts.[25] (ortho-
S43 top). This chemical inequivalence of the methyl groups Amino)phosphane oxides 6 are good candidates as ligands
linked to the prochiral phosphorus atom is attributed to for metal complexes.[26] Transition-metal complexes con-
restricted rotation about the N–Ar bond.[21] This atrop- taining this structural motif have found application, for ex-
isomerism leads to a chiral axis that renders the P–Me ample, as initiators for catalytic ring-opening oligomeriza-
groups diastereotopic.
tion and olefin polymerization and as catalysts for cross-
As far as the reaction products are concerned, only a coupling reactions.[27]
very small number of (2-amino)phenyl phosphonium salts
The isolation of products 6 in these reactions seems to
have been described previously, all of which were prepared indicate that the strong P=O bond is probably not easily
by following the aryl halide–phosphane coupling method of involved in reactions with benzynes (similar to those experi-
Horner and co-workers.[22] Thus, the NiII-catalyzed reaction enced by its P=N analogs 3). Nevertheless, we reasoned that
between 2-chloro(bromo)anilines and tertiary phosphanes compounds bearing weaker and more nucleophilic P=S
(basically triphenylphosphane) at temperatures ranging bonds could be suitable candidates for similar benzyne in-
from 200 to 220 °C resulted in the respective (2-amino)- sertion reactions. Therefore, we next tested similar reactions
phenyl phosphonium salts.[23]
Next, we extended these reactions to the utilization of P- reaction conditions. The first experiment with 7a showed
methoxy-substituted iminophosphoranes (1k–1m, R3
the formation of P-[(2-phenylthio)phenyl]triphenylphos-
with the three phosphane sulfides 7a–7c under comparable
=
OCH3), prepared by Staudinger imination reactions be- phonium triflate (8a) as the major product, although in low
tween methyl diphenylphosphinite (for 1k and 1l) or tri- yield (35%), accompanied by unreacted phosphane sulfide.
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1087

C. Lopez-Leonardo, F. López-Ortiz, M. Alajarin et al.
FULL PAPER
Therefore, we increased the amount of benzyne precursor phosphorus reagents, followed by a retro [2+2] cycload-
2a to 2.6 equiv. and obtained the respective S-phenylated dition and further protonation or reaction with a second
compounds 8 in good yields (Scheme 7, Table 4). The spec- equivalent of benzyne. Variable-temperature NMR spectro-
troscopic and analytical data support the formulation of 8. scopic studies showed that prior to protonation, the reac-
Their NMR spectra show an ortho-substituted phenylphos- tion product exists as a dearomatized phosphorus ylide sta-
phonium moiety and they are similar to those of 3 and 4.
bilized by extended conjugation through a 1,3-cyclohexa-
diene moiety and a carbon–nitrogen double bond. The par-
ticipation of phosphane sulfides in this pathway with a for-
mal carbon–carbon triple bond is described for the first
time. The methodology described here allows an easy entry
to a variety of ortho-functionalized organophosphorus
compounds such as (o-aminophenyl)- and (o-phenylthio)-
phenylphosphonium salts, and (o-aminophenyl)phosphane
oxides, which can be used as precursors or directly as hemil-
abile chelating ligands in coordination chemistry.
Scheme 7. Reaction of benzyne with phosphane sulfides.
Experimental Section
General: All reactions were performed under nitrogen in HPLC
grade solvents (Scharlab), which were nitrogen-saturated, dried,
and deoxygenated by using an Innovative Technology Inc. Pure-
Solv 400 solvent purification system. Column chromatography was
performed with the indicated solvent and silica gel (70–200 μm) as
the stationary phase. Thin layer chromatography (TLC) was per-
formed with silica gel plates. All melting points were determined
with a Kofler hot-plate melting point apparatus. IR spectra were
determined as Nujol emulsions or films with a Nicolet 380 FTIR
spectrophotometer. NMR spectra were recorded at 25 °C with a
Bruker AC200 (200 MHz), Avance 300 (300 MHz), or Avance 400
(400 MHz) spectrometer. Variable-temperature multinuclear mag-
netic resonance spectra were measured with a Bruker Avance 500
spectrometer (500 MHz) equipped with a 5 mm direct 1H/31P/BB
triple resonance broadband (TBO) probe. 1H and 13C chemical
shifts are reported in ppm, referenced to residual H and C in the
deuterated solvent (chloroform, THF) as the internal standard. 7Li,
19F, and 31P chemical shifts were externally referenced to 1 m LiBr
in D2O, trifluorotoluene, and 85% H3PO4, respectively. J values
are given in Hz. A set of two complementary 31P/7Li-selective
band-pass/stop frequency filters was used for the measurement of
Table 4. 2-(Phenylthio)phenylphosphonium triflates 8.
7
R1
R2
R3
Yield of 8 [%]
7a
7b
7c
C6H5
C6H5
C6H5
C6H5
C6H5
CH3
C6H5
CH3
CH3
8a, 70
8b, 87
8c, 73
Similar to those of iminophosphoranes, the reactions of
phosphane sulfides 7 with benzyne most probably proceed
by a [2+2] cycloaddition followed by ring opening to give
the betaines 9, which undergo addition to a second mole-
cule of benzyne to afford the phenylthiophosphonium salts
8. To the best of our knowledge, the reaction of the P=S
linkage with formal acetylenes has no precedent in the lit-
erature.
An exhaustive examination of the chemical literature re-
vealed that a small number of alkyl [(2-methylthio)phen-
yl]diphenylphosphonium salts have been prepared by P-
quaternization of the respective triarylphosphanes with re-
active alkyl halides.[28] In addition, we found that the syn-
thesis of 8a by palladium-mediated aryl–PPh3 coupling has
been previously reported.[29] This is the only example that
we are aware of for the preparation of a (2-arylthio)phenyl
triaryl phosphonium salt, although it yielded only a few
crystals that permitted an X-ray crystal study. In contrast,
the procedure shown in Scheme 7 represents a simple and
efficient method to access this family of compounds in high
yield.
7
NMR spectra involving 31P and Li nuclei. Standard Bruker soft-
ware was used for acquisition and processing routines. Signals in
1
the H and 13C NMR spectra of the synthesized compounds were
1
assigned with the aid of H{31P}, DEPT, and two-dimensional ex-
periments (HMQC). NMR samples of 5f were prepared by using
Schlenk techniques. Mass spectra were recorded with an Agilent
VL (ESI) mass spectrometer.
Materials: Commercially available reagents were used throughout
without purification unless otherwise stated. Compounds 1a,[30]
1b,[31] 1c,[32] 1m,[33] 7a,[34] 7b,[35] and 7c[36] were prepared according
to published procedures.
General Procedure for the Preparation of the Phosphonium Triflates
3: A solution of 2 (0.39 mmol) in anhydrous CH3CN (5 mL) was
added over 2 h to a mixture of 1 (0.3 mmol) and CsF (0.9 mmol)
in anhydrous CH3CN (10 mL) at 0 °C. The resulting mixture was
stirred at 10 °C for 10 h. The reaction mixture was then filtered
through a short pad of Celite to remove insoluble substances. After
concentration of the filtrate under vacuum, the residue was purified
by chromatography on silica and then recrystallized to afford 3.
Conclusions
Herein, we have shown a facile and mild method for the
preparation of P-(2-arylamino)phenyl and P-(2-phenyl-
thio)phenyl phosphonium triflates by reactions of imino-
phosphoranes and phosphane sulfides with (2-trialkylsilyl)-
aryl triflates in the presence of CsF. These reactions most
probably involve the initial π-insertion of the in situ gener-
P-[2-(Benzylamino)phenyl]-P,P,P-triphenylphosphonium
Triflate
ated benzyne into the P=N and P=S bonds of the organo- (3a): The general procedure with 1a (0.11 g, 0.3 mmol) in anhy-
1088 Eur. J. Org. Chem. 2014, 1084–1095
www.eurjoc.org
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

π-Insertion Reactions of Benzynes into P=N and P=S Double Bonds
drous CH3CN (5 mL), 2a (0.12 g, 0.39 mmol) in anhydrous
CH3CN (10 mL), and CsF (0.14 g, 0.9 mmol) afforded 3a as a
white solid, which was purified by flash column chromatography
[gradient eluents: chloroform/methanol 9:1 (v/v) then ethanol; Rf =
0.19, TLC, chloroform/methanol 9:1 (v/v)] and recrystallized from
dichloromethane/diethyl ether; 0.12 g, 70%; white prisms; m.p.
2JP,C = 10.4 Hz, C-6), 137.44 (C-4), 150.47 (d, 2JP,C = 4.5 Hz, C-2),
157.90 (C-4Ј) ppm; CF3SO3 not observable. 19F{1H} NMR
(282 MHz, CDCl3, 25 °C): δ = –78.27 ppm. 31P{1H} NMR
(121 MHz, CDCl , 25 °C): δ = 20.89 ppm. IR (Nujol): ν = 3493
˜
3
(w), 1440 (s), 1262 (vs), 1031 (s), 731 (vs), 636 (s) cm–1. HRMS
(ESI): calcd. for C31H27NOP [M – OTf]+ 460.1825; found 460.1847.
1
196–198 °C. H NMR (400 MHz, CDCl3, 25 °C): δ = 1.85 (s, 1 H,
P,P-Dimethyl-P-[2-(4-methylphenylamino)phenyl]-P-phenylphos-
phonium Triflate (3d): The general procedure with 1f (0.07 g,
0.3 mmol) in anhydrous CH3CN (5 mL), 2a (0.12 g, 0.39 mmol) in
anhydrous CH3CN (10 mL), and CsF (0.14 g, 0.9 mmol) afforded
3d as a white solid, which was purified by successive preparative
TLC [eluent: chloroform/methanol 9:1 (v/v), Rf = 0.24] and recrys-
tallized from dichloromethane/diethyl ether; 0.08 g, 54 %; white
NH), 4.19 (s, 2 H, CH2), 6.75–6.77 (m, 2 H, Ar H), 6.84–6.99 (m,
3 H, Ar H), 7.13–7.19 (m, 3 H, Ar H), 7.62–7.69 (m, 7 H, Ar H),
7.72–7.77 (m, 6 H, Ar H), 7.85–7.89 (m, 3 H, Ar H) ppm. 13C{1H}
1
NMR (75 MHz, CDCl3, 25 °C): δ = 47.96 (CH2), 97.51 (d, JP,C
=
=
3
1
91.4 Hz, C-1), 113.92 (d, JP,C = 7.9 Hz, C-3), 117.07 (d, JP,C
3
88.8 Hz, C-i), 118.93 (d, JP,C = 13.2 Hz, C-5), 127.18 (C-2Ј or C-
3Ј), 127.79 (C-4Ј), 128.76 (C-2Ј or C-3Ј), 130.99 (d, 3JP,C = 12.9 Hz,
1
prisms; m.p. 101–103 °C. H NMR (400 MHz, CDCl3, 25 °C): δ =
2
4
C-m), 134.24 (d, JP,C = 10.4 Hz, C-o), 135.75 (d, JP,C = 2.7 Hz,
C-p), 136.02 (d, JP,C = 10.5 Hz, C-6), 136.76 (C-1Ј), 137.79 (C-4),
151.09 (d, JP,C = 5.1 Hz, C-2) ppm; CF3SO3 not observable.
2.22 (s, 3 H, CH3), 2.52 [d, 2JH,P = 13.6 Hz, 6 H, P(CH3)2], 5.91 (s,
2
3
3
1 H, NH), 6.52 (d, JH,H = 8.2 Hz, 2 H, Ar H), 6.93 (d, JH,H
=
2
8.2 Hz, 2 H, Ar H), 7.31–7.35 (m, 2 H, Ar H), 7.56–7.73 (m, 7 H,
19F{1H} NMR (282 MHz, CDCl3, 25 °C):
δ
=
–78.06 ppm.
Ar H) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25 °C): δ = 9.99 [d,
31P{1H} NMR (121 MHz, CDCl3, 25 °C): δ = 20.54 ppm. IR (Nu-
1
1JP,C = 58.3 Hz, P(CH3)2], 20.64 (CH3), 115.27 (d, JP,C = 91.0 Hz,
jol): ν = 3414 (w), 1440 (m), 1264 (s), 1031 (m), 908 (vs), 733 (vs)
˜
1
C-1), 117.92 (C-2Ј), 120.67 (q, JF,C = 320.1 Hz, CF3SO3), 121.50
cm–1. HRMS (ESI): calcd. for C31H27NP [M – OTf]+ 444.1876;
found 444.1881.
1
3
(d, JP,C = 88.4 Hz, C-i), 125.57 (d, JP,C = 12.8 Hz, C-5), 126.58
3
3
(d, JP,C = 7.5 Hz, C-3), 129.99 (C-3Ј), 130.37 (d, JP,C = 12.7 Hz,
2
P,P,P-Triphenyl-P-[2-(4-methylphenylamino)phenyl]phosphonium
Triflate (3b): The general procedure with 1b (0.11 g, 0.3 mmol) in
anhydrous CH3CN (5 mL), 2a (0.12 g, 0.39 mmol) in anhydrous
CH3CN (10 mL), and CsF (0.14 g, 0.9 mmol) afforded 3b as a yel-
low solid, which was purified by flash column chromatography
[gradient eluents: chloroform/methanol 9:1 (v/v) then ethanol; Rf =
0.23, TLC, chloroform/methanol 9:1 (v/v)] and recrystallized from
dichloromethane/diethyl ether; 0.1 g, 56 %; yellow prisms; m.p.
C-m), 131.21 (d, JP,C = 10.6 Hz, C-o), 131.44 (C-4Ј), 133.80 (d,
2JP,C = 10.3 Hz, C-6), 134.33 (d, JP,C = 2.8 Hz, C-p), 136.47 (d,
4
4JP,C = 2.1 Hz, C-4), 141.37 (C-1Ј), 149.03 (d, JP,C = 4.4 Hz, C-2)
2
ppm. 31P{1H} NMR (121 MHz, CDCl3, 25 °C): δ = 18.01 ppm. IR
(Nujol): ν = 3284 (w), 1513 (m), 1258 (vs), 1031 (s), 910 (s), 733
˜
(vs) cm–1. HRMS (ESI): calcd. for C21H23NP [M – OTf]+ 320.1563;
found 320.1576.
1
P,P-Dimethyl-P-[2-(4-methoxyphenylamino)phenyl]-P-phenylphos-
phonium Triflate (3e): The general procedure with 1g (0.08 g,
0.3 mmol) in anhydrous CH3CN (5 mL), 2a (0.12 g, 0.39 mmol) in
anhydrous CH3CN (10 mL), and CsF (0.14 g, 0.9 mmol) afforded
3e as a white solid, which was purified by successive preparative
TLC [eluent: chloroform/methanol 9:1 (v/v), Rf = 0.19] and recrys-
tallized from dichloromethane/diethyl ether; 0.08 g, 56 %; white
163–165 °C. H NMR (400 MHz, CDCl3, 25 °C): δ = 2.24 (s, 3 H,
3
CH3), 5.19 (s, 1 H, NH), 6.48 (d, JH,H = 8.0 Hz, 2 H, Ar H), 6.97
(d, 3JH,H = 8.0 Hz, 2 H, Ar H), 7.10–7.15 (m, 2 H, Ar H), 7.36 (m,
1 H, Ar H), 7.61–7.72 (m, 1 H, Ar H), 7.73–7.80 (m, 12 H, Ar H),
7.85–7.88 (m, 3 H, Ar H) ppm. 13C{1H} NMR (75 MHz, CDCl3,
1
25 °C): δ = 20.82 (CH3), 104.97 (d, JP,C = 91.7 Hz, C-1), 117.45
1
3
(d, JP,C = 89.6 Hz, C-i), 120.56 (C-2Ј), 120.80 (d, JP,C = 7.7 Hz,
1
1
3
prisms; m.p. 155–157 °C. H NMR (400 MHz, CDCl3, 25 °C): δ =
C-3), 120.97 (q, JF,C = 321.1 Hz, CF3SO3), 123.04 (d, JP, C
12.9 Hz, C-5), 130.24 (C-3Ј), 131.04 (d, JP, C = 12.9 Hz, C-m),
=
2
3
2.53 [d, JP,H = 13.8 Hz, 6 H, P(CH3)2], 3.71 (s, 3 H, OCH3), 5.85
3
3
2
4
(s, 1 H, NH), 6.59 (d, JH,H = 8.9 Hz, 2 H, Ar H), 6.69 (d, JH,H
= 8.9 Hz, 2 H, Ar H), 7.18–7.30 (m, 2 H, Ar H), 7.53–7.75 (m, 7
H, Ar H) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25 °C): δ = 9.92
134.14 (d, JP,C = 10.4 Hz, C-o), 134.59 (C-1Ј), 135.67 (d, JP,C
=
3.0 Hz, C-p), 136.05 (d, 2JP,C = 10.5 Hz, C-6), 137.45 (C-4), 149.54
2
(d, JP,C = 4.4 Hz, C-2) ppm; C-4Ј not observable. 31P{1H} NMR
1
1
[d, JP,C = 58.2 Hz, P(CH3)2], 55.63 (OCH3), 113.26 (d, JP,C
=
=
(121 MHz, CDCl , 25 °C): δ = 20.65 ppm. IR (Nujol): ν = 3397
˜
3
1
(s), 1439 (s), 1275 (vs), 1030 (s), 752 (m), 723 (m) cm–1. HRMS
90.7 Hz, C-1), 114.84 (C-3Ј), 120.44 (C-2Ј), 120.69 (q, JF,C
320.4 Hz, CF3SO3), 121.40 (d, 1JP,C = 88.3 Hz, C-i), 124.67 (d, 3JP,C
(ESI): calcd. for C31H27NP [M – OTf]+ 444.1876; found 444.1897.
3
3
= 12.9 Hz, C-5), 125.00 (d, JP,C = 7.6 Hz, C-3), 130.38 (d, JP,C
12.7 Hz, C-m), 131.26 (d, JP,C = 10.6 Hz, C-o), 133.71 (d, JP,C
10.1 Hz, C-6), 134.38 (d, JP,C = 2.7 Hz, C-p), 136.46 (d, JP,C
=
=
=
P,P,P-Triphenyl-P-[2-(4-methoxyphenylamino)phenyl]phosphonium
Triflate (3c): The general procedure with 1c (0.11 g, 0.3 mmol) in
anhydrous CH3CN (5 mL), 2a (0.12 g, 0.39 mmol) in anhydrous
CH3CN (10 mL), and CsF (0.14 g, 0.9 mmol) afforded 3c as a yel-
low solid, which was purified by flash column chromatography
[gradient eluents: chloroform/methanol 9:1 (v/v) then ethanol; Rf =
0.21, TLC, chloroform/methanol 9:1 (v/v)] and recrystallized from
2
2
4
4
2
1.6 Hz, C-4), 136.62 (C-1Ј), 149.82 (d, JP,C = 4.4 Hz, C-2), 155.40
(C-4Ј) ppm. 31P{1H} NMR (121 MHz, CDCl3, 25 °C): δ =
18.28 ppm. IR (Nujol): ν = 3290 (m), 1511 (vs), 1257 (vs), 1031 (s),
˜
755 (vs), 638 (s) cm–1. HRMS (ESI): calcd. for C21H23NOP [M –
OTf]+ 336.1512; found 336.1516.
dichloromethane/diethyl ether; 0.12 g, 65%; yellow prisms; m.p.
1
178–180 °C. H NMR (400 MHz, CDCl3, 25 °C): δ = 3.74 (s, 3 H, P,P-Dimethyl-P-[2-(2,6-dimethylphenylamino)phenyl]-P-phenylphos-
3
OCH3), 5.15 (s, 1 H, NH), 6.58 (d, JH,H = 8.9 Hz, 2 H, Ar H),
phonium Triflate (3f): The general procedure with 1h (0.08 g,
0.3 mmol) in anhydrous CH3CN (5 mL), 2a (0.12 g, 0.39 mmol) in
anhydrous CH3CN (10 mL), and CsF (0.14 g, 0.9 mmol) afforded
3
6.75 (d, JH,H = 8.9 Hz, 2 H, Ar H), 7.03–7.08 (m, 2 H, Ar H),
7.15–7.19 (m, 1 H, Ar H), 7.60–7.65 (m, 1 H, Ar H), 7.70–7.80 (m,
12 H, Ar H), 7.86–7.90 (m, 3 H, Ar H) ppm. 13C{1H} NMR 3f as a white solid, which was purified by flash column chromatog-
1
(75 MHz, CDCl3, 25 °C): δ = 55.64 (OCH3), 102.76 (d, JP,C
=
raphy [gradient eluents: chloroform/methanol 9:1 (v/v) then eth-
91.7 Hz, C-1), 115.06 (C-3Ј), 117.42 (d, 1JP,C = 89.3 Hz, C-i), 119.23 anol; Rf = 0.14, TLC, chloroform/methanol 9:1 (v/v)] and recrys-
3
3
(d, JP,C = 7.5 Hz, C-3), 122.01 (d, JP,C = 13.0 Hz, C-5), 123.82
tallized from dichloromethane/diethyl ether; 0.11 g, 75%; white
3
1
(C-2Ј), 131.07 (d, JP,C = 12.9 Hz, C-m), 132.42 (C-1Ј), 134.21 (d,
prisms; m.p. 195–197 °C. H NMR (400 MHz, CDCl3, 25 °C): δ =
2JP,C = 10.4 Hz, C-o), 135.60 (d, JP,C = 2.8 Hz, C-p), 135.94 (d,
1.78 (s, 6 H, CH3), 2.67 [d, JP,H = 14.0 Hz, 6 H, P(CH3)2], 4.81 (s,
4
2
Eur. J. Org. Chem. 2014, 1084–1095
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1089

C. Lopez-Leonardo, F. López-Ortiz, M. Alajarin et al.
FULL PAPER
3
4
1 H, NH), 6.38 (dd, JH,H = 8.3 Hz, JP,H = 6.1 Hz, 1 H, Ar H), 2.8 Hz, C-p), 134.28 (C-2Ј), 137.25 (C-1Ј), 137.39 (C-4), 152.30 (d,
7.02–7.08 (m, 3 H, Ar H), 7.15 (t, 3JH,H = 7.6 Hz, 1 H, Ar H), 7.48 2JP,C = 2.8 Hz, C-2), 163.63 (C-6) ppm. 19F{1H} NMR (282 MHz,
3
(t, JH,H = 7.6 Hz, 1 H, Ar H), 7.69–7.75 (m, 3 H, Ar H), 7.77–
CDCl3, 25 °C): δ = –78.22 ppm. 31P{1H} NMR (121 MHz, CDCl3,
7.81 (m, 1 H, Ar H), 7.90–7.95 (dd, 3JP,H = 8.5 Hz, 3JH,H = 7.1 Hz,
25 °C): δ = 17.56 ppm. IR (Nujol): ν = 3330 (m), 1467 (vs), 1438
˜
2 H, Ar H) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25 °C): δ = (s), 1262 (vs), 733 (m), 638 (vs) cm–1. HRMS (ESI): calcd. for
1
1
8.43 [d, JP,C = 57.6 Hz, P(CH3)2], 18.00 (CH3), 102.78 (d, JP,C
=
=
C23H27NOP [M – OTf]+ 364.1825; found 364.1831.
3
1
88.6 Hz, C-1), 115.91 (d, JP,C = 7.6 Hz, C-3), 120.66 (d, JP,C
General Procedure for the Preparation of the Phosphonium Triflates
4: A solution of 2 (0.78 mmol) in anhydrous CH3CN (5 mL) was
added over 2 h to a mixture of 1 (0.3 mmol) and CsF (0.9 mmol)
in anhydrous CH3CN (10 mL) at 0 °C. The resulting mixture was
stirred at 10 °C for 10 h. The reaction mixture was then filtered
through a short pad of Celite to remove insoluble substances. After
concentration of the filtrate under vacuum, the residue was purified
by flash column chromatography on silica and then recrystallized
to afford 4.
84.1 Hz, C-i), 120.74 (q, 1JF,C = 320.3 Hz, CF3SO3), 121.25 (d, 3JP,C
3
= 12.6 Hz, C-5), 126.78 (C-4Ј), 129.14 (C-3Ј), 131.15 (d, JP,C
12.6 Hz, C-m), 131.64 (d, JP,C = 11.0 Hz, C-o), 133.64 (d, JP,C
=
=
2
2
4
9.5 Hz, C-6), 134.10 (C-2Ј), 135.25 (d, JP,C = 2.8 Hz, C-p), 136.12
4
2
(C-1Ј), 136.98 (d, JP,C = 2.2 Hz, C-4), 149.05 (d, JP,C = 4.5 Hz,
C-2) ppm. 31P{1H} NMR (162 MHz, CDCl3, 25 °C): δ =
18.40 ppm. IR (Nujol): ν = 3391 (w), 1449 (m), 1266 (vs), 1030 (s),
˜
738 (vs), 638 (s) cm–1. HRMS (ESI): calcd. for C22H25NP [M –
OTf]+ 334.1719; found 334.1719.
P-Methyl-P-{2-[(N-4-methoxyphenyl-N-phenyl)amino]phenyl}-P,P-
diphenylphosphonium Triflate (4a): The general procedure with 1d
(0.1 g, 0.3 mmol) in anhydrous CH3CN (5 mL), 2a (0.23 g,
0.78 mmol) in anhydrous CH3CN (10 mL), and CsF (0.14 g,
0.9 mmol) afforded 4a as a yellow solid, which was purified by flash
column chromatography [gradient eluents: chloroform/methanol
9:1 (v/v) then ethanol; Rf = 0.2, TLC, chloroform/methanol 9:1 (v/
v)] and recrystallized from dichloromethane/diethyl ether; 0.11 g,
74%; yellow prisms; m.p. 158–160 °C. 1H NMR (400 MHz, CDCl3,
P,P-Dimethyl-P-[6-methoxy-2-(4-methoxyphenylamino)phenyl]-P-
phenylphosphonium Triflate (3 g): The general procedure with 1g
(0.08 g, 0.3 mmol) in anhydrous CH3CN (5 mL), 2b (0.13 g,
0.39 mmol) in anhydrous CH3CN (10 mL), and CsF (0.14 g,
0.9 mmol) afforded 3g as a white solid, which was purified by flash
column chromatography [gradient eluents: chloroform/methanol
9:1 (v/v) then ethanol; Rf = 0.24, TLC, chloroform/methanol 9:1
(v/v)] and recrystallized from dichloromethane/diethyl ether; 0.11 g,
72%; white prisms; m.p. 150–152 °C. 1H NMR (400 MHz, CDCl3,
2
2
25 °C): δ = 2.91 (d, JP,H = 13.7 Hz, 3 H, PCH3), 3.70 (s, 3 H,
25 °C): δ = 2.50 [d, JP,H = 14.0 Hz, 6 H, P(CH3)2], 3.48 (s, 3 H,
3
3
3
4
OCH3), 6.58 (d, JH,H = 9.0 Hz, 2 H, Ar H), 6.67 (d, JH,H
=
OCH3), 3.75 (s, 3 H, OCH3), 6.49 (dd, JH,H = 8.0 Hz, JP,H
=
3
3
9.0 Hz, 2 H, Ar H), 6.72 (d, JH,H = 7.9 Hz, 2 H, Ar H), 6.87 (t,
4.8 Hz, 1 H, Ar H), 6.79 (d, JH,H = 8.8 Hz, 2 H, Ar H), 6.92 (dd,
3JH,H = 8.0 Hz, 4JP,H = 5.2 Hz, 1 H, Ar H), 6.98 (d, 3JH,H = 8.8 Hz,
2 H, Ar H), 7.03 (s, 1 H, NH), 7.42 (t, 3JH,H = 8.0 Hz, 1 H, Ar H),
7.51–7.60 (m, 5 H, Ar H) ppm. 13C{1H} NMR (100 MHz, CDCl3,
25 °C): δ = 12.61 [d, 1JP,C = 57.8 Hz, P(CH3)2], 55.70 (OCH3), 55.96
3JH,H = JH,H = 7.9 Hz, 1 H, Ar H), 7.08 (t, JH,H = 7.9 Hz, 2 H,
4
3
3
3
4
Ar H), 7.26 (ddd, JP,H = 15.0 Hz, JH,H = 8.0 Hz, JH,H = 1.1 Hz,
1 H, Ar H), 7.34–7.42 (m, 6 H, Ar H), 7.49–7.54 (m, 4 H, Ar H),
3
7.63–7.67 (m, 2 H, Ar H), 7.74 (t, JH,H = 7.7 Hz, 1 H, Ar H)
1
ppm. 13C{1H} NMR (100 MHz, CDCl3, 25 °C): δ = 8.89 (d, JP,C
1
3
(OCH3), 97.79 (d, JP,C = 93.0 Hz, C-1), 105.08 (d, JP,C = 4.6 Hz,
1
C-3), 115.04 (C-3Ј), 115.87 (d, 3JP,C = 6.7 Hz, C-5), 120.81 (q, 1JF,C
= 58.8 Hz, PCH3), 55.47 (OCH3), 114.97 (C-3Ј), 116.88 (d, JP,C
=
=
1
1
1
87.8 Hz, C-i), 119.14 (d, JP,C = 88.2 Hz, C-1), 120.91 (q, JF,C
= 317.7 Hz, CF3SO3), 120.87 (C-2Ј), 126.53 (d, JP,C = 91.0 Hz, C-
2
3
320.9 Hz, CF3SO3), 122.15 (C-2ЈЈ), 123.42 (C-4ЈЈ), 125.52 (C-2Ј),
i), 129.64 (d, JP,C = 10.4 Hz, C-o), 129.83 (d, JP,C = 12.9 Hz, C-
m), 133.20 (C-p), 136.14 (C-1Ј), 137.00 (C-4), 152.13 (C-2), 155.44
(C-4Ј), 163.15 (C-6) ppm. 19F{1H} NMR (282 MHz, CDCl3,
25 °C): δ = –78.29 ppm. 31P{1H} NMR (121 MHz, CDCl3, 25 °C):
3
3
126.86 (d, JP,C = 12.9 Hz, C-5), 129.56 (C-3ЈЈ), 130.22 (d, JP,C
=
13.0 Hz, C-m), 132.63 (d, 2JP,C = 10.4 Hz, C-o and C-3), 134.47 (C-
p), 136.83 (d, JP,C = 1.9 Hz, C-4), 137.62 (d, JP,C = 10.1 Hz, C-
4
2
2
6), 139.18 (C-1Ј), 147.49 (C-1ЈЈ), 153.01 (d, JP,C = 4.4 Hz, C-2),
δ = 17.92 ppm. IR (Nujol): ν = 3315 (w), 1511 (s), 1467 (s), 1439
˜
156.39 (C-4Ј) ppm. 31P{1H} NMR (162 MHz, CDCl3, 25 °C): δ =
(s), 1265 (vs), 1246 (vs), 1031 (s), 738 (vs), 639 (s) cm–1. HRMS
(ESI): calcd. for C22H25NO2P [M – OTf]+ 366.1617; found
366.1625.
20.30 ppm. IR (Nujol): ν = 1507 (vs), 1439 (s), 1262 (vs), 1031 (vs),
˜
910 (vs), 734 (vs) cm–1. HRMS (ESI): calcd. for C32H29NOP [M –
OTf]+ 474.1981; found 474.1988.
P,P-Dimethyl-P-[2-(2,6-dimethylphenylamino)-6-methoxy]phenyl-P-
phenylphosphonium Triflate (3h): The general procedure with 1h
P-{2-[(N-4-Bromophenyl-N-phenyl)amino]phenyl}-P-methyl-P,P-di-
(0.08 g, 0.3 mmol) in anhydrous CH3CN (5 mL), 2b (0.13 g, phenylphosphonium Triflate (4b): The general procedure with 1e
0.39 mmol) in anhydrous CH3CN (10 mL), and CsF (0.14 g,
0.9 mmol) afforded 3h as a white solid, which was purified by flash
column chromatography [gradient eluents: chloroform/methanol
9:1 (v/v) then ethanol; Rf = 0.30, TLC, chloroform/methanol 9:1
(v/v)] and recrystallized from dichloromethane/diethyl ether; 0.07 g,
48%; white prisms; m.p. 183–185 °C. 1H NMR (400 MHz, CDCl3,
25 °C): δ = 2.02 (s, 6 H, CH3), 2.66 [d, 2JP,H = 14.0 Hz, 6 H, P(CH3)
2], 3.64 (s, 3 H, OCH3), 5.80 (s, 1 H, NH), 6.07 (dd, 3JH,H = 8.3 Hz,
(0.11 g, 0.3 mmol) in anhydrous CH3CN (5 mL), 2a (0.23 g,
0.78 mmol) in anhydrous CH3CN (10 mL), and CsF (0.14 g,
0.9 mmol) afforded 4b as a yellow solid, which was purified by flash
column chromatography [gradient eluents: chloroform/methanol
9:1 (v/v) then ethanol; Rf = 0.2, TLC, chloroform/methanol 9:1 (v/
v)] and recrystallized from dichloromethane/diethyl ether; 0.16 g,
87%; yellow prisms; m.p. 158–160 °C. 1H NMR (300 MHz, CDCl3,
2
3
25 °C): δ = 2.95 (d, JP,H = 13.5 Hz, 3 H, PCH3), 6.64 (d, JH,H
=
3
4JP,H = 5.3 Hz, 1 H, Ar H), 6.47 (dd, 3JH,H = 8.3 Hz, 4JP,H = 4.9 Hz, 9.0 Hz, 2 H, Ar H), 6.78 (d, JH,H = 7.5 Hz, 2 H, Ar H), 6.88 (t,
3
1 H, Ar H), 7.05 (br s, 3 H, Ar H), 7.33 (t, JH,H = 8.3 Hz, 1 H, 3JH,H = 7.5 Hz, 1 H, Ar H), 7.08–7.13 (m, 4 H, Ar H), 7.29–7.48
Ar H), 7.59–7.66 (m, 2 H, Ar H), 7.67–7.74 (m, 3 H, Ar H) ppm.
(m, 7 H, Ar H), 7.49–7.54 (m, 4 H, Ar H), 7.56–7.68 (m, 2 H, Ar
1
3
13C{1H} NMR (100 MHz, CDCl3, 25 °C): δ = 12.76 [d, JP,C
=
=
=
H), 7.78 (t, JH,H = 7.8 Hz, 1 H, Ar H) ppm. 13C{1H} NMR
1
1
57.2 Hz, P(CH3)2], 18.41 (CH3), 56.03 (OCH3), 92.19 (d, JP,C
(75 MHz, CDCl3, 25 °C): δ = 8.84 (d, JP,C = 58.6 Hz, PCH3),
3
3
1
1
92.5 Hz, C-1), 103.38 (d, JP,C = 6.1 Hz, C-3), 110.59 (d, JP,C
116.91 (C-4Ј), 117.75 (d, JP,C = 87.6 Hz, C-i), 118.48 (d, JP,C =
7.8 Hz, C-5), 120.73 (q, 1JF,C = 320.3 Hz, CF3SO3), 125.68 (d, 1JP,C
95.3 Hz, C-1), 120.90 (q, JF,C = 320.9 Hz, CF3SO3), 123.17 (C-
1
2
= 88.6 Hz, C-i), 126.27 (C-4Ј), 129.05 (C-3Ј), 129.97 (d, JP,C
=
=
2ЈЈ), 124.45 (C-4ЈЈ), 124.62 (C-2Ј), 127.66 (d, 3JP,C = 12.8 Hz, C-5),
3
4
3
10.5 Hz, C-o), 130.47 (d, JP,C = 12.6 Hz, C-m), 133.91 (d, JP,C
129.84 (C-3Ј), 130.34 (d, JP, C = 13.0 Hz, C-m), 132.61 (C-3ЈЈ),
1090
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2014, 1084–1095

π-Insertion Reactions of Benzynes into P=N and P=S Double Bonds
2
2
132.72 (d, JP,C = 10.6 Hz, C-o), 133.07 (d, JP,C = 8.2 Hz, C-3),
(vs), 911 (s), 732 (vs) cm–1. HRMS (ESI): calcd. for C27H27NOP
[M – OTf]+ 412.1825; found 412.1830.
2
134.56 (C-p), 137.08 (C-4), 137.72 (d, JP,C = 10.0 Hz, C-6), 145.55
(C-1Ј or C-1ЈЈ), 146.17 (C-1Ј or C-1ЈЈ), 151.90 (d, 2JP,C = 4.4 Hz, C-
2) ppm. 19F{1H} NMR (282 MHz, CDCl3, 25 °C): δ = –78.20 ppm.
31P{1H} NMR (121 MHz, CDCl3, 25 °C): δ = 20.81 ppm. IR (Nu-
P-{2-[(N-4-bromophenyl-N-Phenyl)amino]phenyl}-P,P-dimethyl-P-
phenylphosphonium Triflate (4e): The general procedure with 1i
(0.09 g, 0.3 mmol) in anhydrous CH3CN (5 mL), 2a (0.23 g,
0.78 mmol) in anhydrous CH3CN (10 mL), and CsF (0.14 g,
0.9 mmol) afforded 4e as a yellow solid, which was purified by flash
column chromatography [gradient eluents: chloroform/methanol
9:1 (v/v) then ethanol; Rf = 0.2, TLC, chloroform/methanol 9:1
(v/v)] and recrystallized from dichloromethane/diethyl ether; 0.14 g,
jol): ν = 1487 (m), 1261 (s), 1031 (m), 908 (vs), 733 (vs) cm–1.
˜
HRMS (ESI): calcd. for C31H26BrNP [M – OTf]+ 522.0981; found
522.0984.
P,P-Dimethyl-P-phenyl-P-[2-(N-phenyl-N-4-methylphenyl)amino]-
phenylphosphonium Triflate (4c): The general procedure with 1f
(0.07 g, 0.3 mmol) in anhydrous CH3CN (5 mL), 2a (0.23 g, 76%; white prisms; m.p. 163–165 °C. 1H NMR (400 MHz, CDCl3,
2
3
0.78 mmol) in anhydrous CH3CN (10 mL), and CsF (0.14 g,
0.9 mmol) afforded 4c as a white solid, which was purified by flash
column chromatography [gradient eluents: chloroform/methanol
9:1 (v/v) then ethanol; Rf = 0.33, TLC, chloroform/methanol 9:1
(v/v)] and recrystallized from dichloromethane/diethyl ether; 0.11 g,
65%; white prisms; m.p. 183–185 °C. 1H NMR (400 MHz, CDCl3,
25 °C): δ = 2.21 (s, 3 H, CH3), 2.32 [d, 2JP,H = 13.6 Hz, 6 H, P(CH3)
25 °C): δ = 2.39 [d, JP,H = 13.6 Hz, 6 H, P(CH3)2], 6.52 (d, JH,H
3
= 8.8 Hz, 2 H, Ar H), 6.69 (d, JH,H = 7.8 Hz, 2 H, Ar H), 6.96 (t,
3JH,H = 7.8 Hz, 1 H, Ar H), 7.11 (d, JH,H = 8.8 Hz, 2 H, Ar H),
3
7.13 (t, 3JH,H = 7.8 Hz, 2 H, Ar H), 7.22 (dd, 3JH,H = 7.7 Hz, JP,H
4
= 5.6 Hz, 1 H, Ar H), 7.36–7.39 (m, 4 H, Ar H), 7.50–7.57 (m, 1
3
3
H, Ar H), 7.62 (t, JH,H = 7.7 Hz, 1 H, Ar H), 7.75 (t, JH,H
=
3
3
7.7 Hz, 1 H, Ar H), 8.08 (dd, JP,H = 14.7 Hz, JH,H = 7.7 Hz, 1
3
3
2], 6.53 (d, JH,H = 8.2 Hz, 2 H, Ar H), 6.66 (d, JH,H = 8.4 Hz, 2
H, Ar H) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25 °C): δ = 9.22
3
3
1
1
H, Ar H), 6.88 (d, JH,H = 8.2 Hz, 2 H, Ar H), 6.93 (t, JH,H
=
(d, JP, C = 55.8 Hz, PCH3), 10.53 (d, JP,C = 57.6 Hz, PCH3),
116.63 (C-4Ј), 118.53 (d, JP,C = 86.7 Hz, C-1 or C-i), 120.28 (d,
3
1
8.4 Hz, 1 H, Ar H), 7.11 (t, JH,H = 8.4 Hz, 2 H, Ar H), 7.23 (t,
3JH,H = 6.7 Hz, 1 H, Ar H), 7.38–7.45 (m, 4 H, Ar H), 7.51–7.59 1JP,C = 87.9 Hz, C-1 or C-i), 120.74 (q, 1JF,C = 320.5 Hz, CF3SO3),
3
3
(m, 2 H, Ar H), 7.72 (t, JH,H = 7.7 Hz, 1 H, Ar H), 7.98 (dd,
122.83 (C-2ЈЈ), 124.06 (C-2Ј), 124.36 (C-4ЈЈ), 128.20 (d, JP, C
=
3JP,H = 14.9 Hz, JH,H = 7.9 Hz, 1 H, Ar H) ppm. 13C{1H} NMR
12.9 Hz, C-5), 129.83 (C-3ЈЈ), 129.92 (d, JP, C = 13.1 Hz, C-m),
3
3
1
2
3
(100 MHz, CDCl3, 25 °C): δ = 9.96 [d, JP,C = 57.8 Hz, P(CH3)2],
130.83 (d, JP,C = 10.7 Hz, C-o), 132.48 (C-3Ј) 132.52 (d, JP,C
=
=
1
4
2
20.70 (CH3), 118.11 (d, JP,C = 86.8 Hz, C-1 or C-i), 120.62 (d, 8.2 Hz, C-3), 133.73 (d, JP,C = 3.0 Hz, C-p), 136.09 (d, JP,C
1JP,C = 88.5 Hz, C-1 or C-i), 120.78 (q, 1JF,C = 320.4 Hz, CF3SO3),
9.6 Hz, C-6), 136.82 (d, JP,C = 2.4 Hz, C-4), 145.80 (C-1Ј or C-
1ЈЈ), 146.46 (C-1Ј or C-1ЈЈ), 150.79 (d, JP,C = 3.9 Hz, C-2) ppm.
4
3
2
122.50 (C-2ЈЈ), 123.10 (C-2Ј), 123.72 (C-4ЈЈ), 127.57 (d, JP, C
=
12.5 Hz, C-5), 129.58 (C-3ЈЈ), 129.82 (d, JP, C = 13.1 Hz, C-m), 31P{1H} NMR (162 MHz, CDCl3, 25 °C): δ = 18.15 ppm. IR (Nu-
3
2
3
130.24 (C-3Ј), 130.96 (d, JP,C = 10.7 Hz, C-o), 132.36 (d, JP,C
8.0 Hz, C-3), 133.67 (d, JP,C = 3.0 Hz, C-p), 133.93 (C-4Ј), 135.92
(d, JP,C = 9.8 Hz, C-6), 136.63 (d, JP,C = 2.4 Hz, C-4), 144.32 (C- 460.0825.
=
jol): ν = 1487 (vs), 1260 (vs), 1031 (vs), 911 (s), 731 (vs) cm–1.
˜
4
HRMS (ESI): calcd. for C26H24BrNP [M –OTf]+ 460.0824; found
2
4
2
1Ј or C-1ЈЈ), 147.37 (C-1Ј or C-1ЈЈ), 151.83 (d, JP,C = 4.0 Hz, C-2)
ppm. 31P{1H} NMR (162 MHz, CDCl3, 25 °C): δ = 18.08 ppm. IR
P-{2-[(N-4-nitrophenyl-N-phenyl)amino]phenyl}-P,P-dimethyl-P-
(Nujol): ν = 1508 (s), 1259 (vs), 1030 (s), 933 (m), 734 (m) cm–1.
phenylphosphonium Triflate (4f): The general procedure with 1j
(0.08 g, 0.3 mmol) in anhydrous CH3CN (5 mL), 2a (0.23 g,
0.78 mmol) in anhydrous CH3CN (10 mL), and CsF (0.14 g,
0.9 mmol) afforded 4f as a yellow solid, which was purified by flash
column chromatography [gradient eluents: chloroform/methanol
9:1 (v/v) then ethanol; Rf = 0.2, TLC, chloroform/methanol 9:1 (v/
˜
HRMS (ESI): calcd. for C27H27NP [M – OTf]+ 396.1876; found
396.1876.
P,P-Dimethyl-P-phenyl-P-[2-(N-phenyl-N-4-methoxyphenyl)amino]-
phenylphosphonium Triflate (4d): The general procedure with 1g
(0.08 g, 0.3 mmol) in anhydrous CH3CN (5 mL), 2a (0.23 g, v)] and recrystallized from dichloromethane/diethyl ether; 0.12 g,
0.39 mmol) in anhydrous CH3CN (10 mL), and CsF (0.14 g,
0.9 mmol) afforded 4d as a white solid, which was purified by flash
column chromatography [gradient eluents: chloroform/methanol
9:1 (v/v) then ethanol; Rf = 0.3, TLC, chloroform/methanol 9:1 (v/
69%; white prisms; m.p. 124–126 °C. 1H NMR (400 MHz, CDCl3,
2
2
25 °C): δ = 2.34 (d, JP,H = 14.0 Hz, 3 H, PCH3), 2.47 (d, JP,H
=
13.6 Hz, 3 H, PCH3), 6.76 (d, 3JH,H = 9.2 Hz, 2 H, Ar H), 6.77 (d,
3
3JH,H = 8.1 Hz, 2 H, Ar H), 7.04 (t, JH,H = 7.4 Hz, 1 H, Ar H),
3
3
v)] and recrystallized from dichloromethane/diethyl ether; 0.12 g, 7.18 (dd, JH,H = 8.1 Hz, JH,H = 7.4 Hz, 2 H, Ar H), 7.28–7.40
72%; white prisms; m.p. 171–173 °C. 1H NMR (400 MHz, CDCl3,
(m, 5 H, Ar H), 7.44–7.50 (m, 1 H, Ar H), 7.72 (t, JH,H = 7.9 Hz,
3
2
3
3
25 °C): δ = 2.33 [d, JP,H = 13.6 Hz, 6 H, P(CH3)2], 3.72 (s, 3 H,
1 H, Ar H), 7.83 (t, JH,H = 7.9 Hz, 1 H, Ar H), 7.86 (d, JH,H =
3
3
3
OCH3), 6.56–6.64 (m, 6 H, Ar H), 6.92 (t, JH,H = 7.4 Hz, 1 H, Ar 9.2 Hz, 2 H, Ar H), 8.14 (ddd, JP,H = 14.8 Hz, JH,H = 7.9 Hz,
3
3
H), 7.10 (t, JH,H = 7.4 Hz, 2 H, Ar H), 7.22 (t, JH,H = 8.0 Hz, 1
4JH,H = 1.2 Hz, 1 H, Ar H) ppm. 13C{1H} NMR (100 MHz,
1
1
H, Ar H), 7.41–7.46 (m, 4 H, Ar H), 7.52–7.58 (m, 2 H, Ar H), CDCl3, 25 °C): δ = 9.33 (d, JP,C = 57.6 Hz, PCH3), 10.10 (d, JP,C
7.72 (t, 3JH,H = 8.0 Hz, 1 H, Ar H), 7.97 (dd, 3JP,H = 14.9 Hz, 3JH,H = 58.1 Hz, PCH3), 119.16 (d, JP,C = 86.4 Hz, C-1 or C-i), 120.06
1
= 8.0 Hz, 1 H, Ar H) ppm. 13C{1H} NMR (100 MHz, CDCl3, (d, JP,C = 87.5 Hz, C-1 or C-i), 120.31 (C-2Ј), 120.71 (q, JF,C
=
1
1
25 °C): δ = 9.96 [d, 1JP,C = 58.5 Hz, P(CH3)2], 55.51 (OCH3), 114.91 320.5 Hz, CF3SO3), 123.89 (C-2ЈЈ), 125.35 (C-3Ј), 125.80 (C-4ЈЈ),
1
1
3
3
(C-3Ј), 117.76 (d, JP,C = 86.9 Hz, C-1 or C-i), 120.73 (d, JP,C
=
129.30 (d, JP,C = 12.3 Hz, C-5), 129.86 (d, JP,C = 13.2 Hz, C-m),
1
2
3
88.4 Hz, C-1 or C-i), 120.78 (q, JF,C = 320.4 Hz, CF3SO3), 122.07 130.15 (C-3ЈЈ), 130.89 (d, JP,C = 10.7 Hz, C-o), 132.96 (d, JP,C
(C-2ЈЈ), 123.48 (C-4ЈЈ), 124.93 (C-2Ј), 127.36 (d, JP,C = 12.7 Hz, 7.9 Hz, C-3), 133.97 (d, JP,C = 2.4 Hz, C-p), 136.48 (d, JP,C
=
=
3
4
2
3
C-5), 129.58 (C-3ЈЈ), 129.84 (d, JP,C = 12.9 Hz, C-m), 130.93 (d, 9.4 Hz, C-6), 137.14 (C-4), 142.21 (C-4Ј), 144.35 (C-1ЈЈ), 149.22 (d,
2JP,C = 10.6 Hz, C-o), 132.09 (d, JP,C = 8.0 Hz, C-3), 133.80 (d,
2JP,C = 3.6 Hz, C-2), 152.19 (C-1Ј) ppm. 19F{1H} NMR (282 MHz,
3
4JP,C = 2.8 Hz, C-p), 135.90 (d, 2JP,C = 9.9 Hz, C-6), 136.62 (d, 4JP,C
CDCl3, 25 °C): δ = –78.30 ppm. 31P{1H} NMR (162 MHz, CDCl3,
2
= 2.1 Hz, C-4), 139.87 (C-1Ј), 147.79 (C-1ЈЈ), 152.02 (d, JP,C
=
25 °C): δ = 18.76 ppm. IR (Nujol): ν = 1492 (m), 1270 (s), 1031
˜
3.9 Hz, C-2), 156.41 (C-4Ј) ppm. 31P{1H} NMR (162 MHz, CDCl3, (m), 908 (vs), 732 (vs) cm–1. HRMS (ESI): calcd. for C26H24N2O2P
25 °C): δ = 18.08 ppm. IR (Nujol): ν = 1507 (s), 1260 (vs), 1031 [M – OTf]+ 427.1570; found 427.1581.
˜
Eur. J. Org. Chem. 2014, 1084–1095
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1091

C. Lopez-Leonardo, F. López-Ortiz, M. Alajarin et al.
FULL PAPER
o-Azaphosphaxylydene (5f): To a solution of 3f (49.0 mg, 0.1 mmol)
in dry [D8]THF (1 mL, distilled from sodium/benzophenone imme-
diately prior to use) at –78 °C was added nBuLi (1.6 m solution in
hexanes; 70 μL, 0.11 mmol). The reaction mixture was stirred for
5 min, and then a portion (0.6 mL) of the yellow solution formed
was quickly transferred by syringe to a dried 5 mm NMR tube
cooled to –78 °C under an inert atmosphere. The sample was trans-
ferred into the bore of the magnet precooled to –50 °C. The extra
signals in the spectra correspond to the solvent of the organo-
lithium base, which was not eliminated. 1H NMR (500.13 MHz,
which was purified by column chromatography [eluent: hexanes/
ethyl acetate 1:1 (v/v), Rf = 0.42] and recrystallized from chloro-
form/n-pentane; 0.12 g, 86%; white prisms; m.p. 169–171 °C. 1H
NMR (400 MHz, CDCl3, 25 °C): δ = 6.75–6.79 (m, 1 H, Ar H),
6.88 (ddd, JP,H = 15.8 Hz, JH,H = 7.6 Hz, JH,H = 1.3 Hz, 1 H,
Ar H), 6.95 (d, 3JH,H = 8.8 Hz, 2 H, Ar H), 7.29 (d, 3JH,H = 8.8 Hz,
2 H, Ar H), 7.32–7.37 (m, 2 H, Ar H), 7.44–7.48 (m, 4 H, Ar H),
7.53–7.57 (m, 2 H, Ar H), 7.62–7.67 (m, 4 H, Ar H) ppm; NH not
observable. 13C{1H} NMR (100 MHz, CDCl3, 25 °C): δ = 114.14
3
3
4
1
3
(C-4Ј), 116.01 (d, JP,C = 103.0 Hz, C-1), 116.04 (d, JP,C = 7.6 Hz,
2
3
[D8]THF, –30 °C): δ = 1.83 (s, 6 H, CH3), 2.37 [d, JP,H = 14.3 Hz,
C-3), 118.94 (d, JP,C = 12.7 Hz, C-5), 121.58 (C-2Ј), 128.65 (d,
6 H, P(CH3)2], 5.58 (dd, 3JH,H = 7.7 Hz, 4JP,H = 6.5 Hz, 1 H, 3-H),
3JP,C = 12.2 Hz, C-m), 131.87 (d, JP,C = 104.4 Hz, C-i), 132.08 (d,
1
3
4
3
4
5.7 (dt, JH,H = 7.7 Hz, JP,H = 4.1 Hz, 1 H, 5-H), 6.52 (t, JH,H
=
2JP,C = 10.0 Hz, C-o), 132.09 (C-p and C-3Ј), 133.34 (d, JP,C
=
7.3 Hz, 1 H, 4Ј-H), 6.69 (t, 3JH,H = 7.7 Hz, 1 H, 4-H), 6.77 (t, 3JH,H 1.6 Hz, C-4), 133.91 (d, 2JP,C = 10.9 Hz, C-6), 140.84 (C-1Ј), 149.22
= 7.7 Hz, JP,H = 14.3 Hz, 1 H, 6-H), 6.81 (d, JH,H = 7.3 Hz, 2 H,
3
3
2
(d, JP,C = 2.8 Hz, C-2) ppm. 31P{1H} NMR (162 MHz, CDCl3,
3
4
3Ј-H), 7.56 (dt, JH,H = 7.4, JP,H = 2.3 Hz, 2 H, m-H), 7.63 (t, 25 °C): δ = 36.23 ppm. IR (Nujol): ν = 1591 (vs), 1570 (vs), 1450
˜
3JH,H = 7.4 Hz, 1 H, p-H), 7.89 (dd, JH,H = 7.4 Hz, JP, H
=
(vs), 1119 (m), 728 (vs), 694 (s) cm–1. HRMS (ESI): calcd. for
C24H20BrNOP [M + H]+ 448.0460; found 448.0443.
3
3
12.8 Hz, 2 H, o-H) ppm. 13C{1H} NMR (125.758 MHz, [D8]THF,
1
–30 °C): δ = 7.88 [d, JP,C = 60.6 Hz, P(CH3)2], 18.56 (CH3), 90.61
(d, JP,C = 103.0 Hz, C-1), 104.29 (d, JP,C = 14.8 Hz, C-5), 111.91
P-[2-(4-Bromophenylamino)methoxyphenyl]-P,P-diphenylphosphane
Oxide (6c): The general procedure with 1l (0.12 g, 0.3 mmol) in
anhydrous CH3CN (5 mL), 2b (0.13 g, 0.39 mmol) in anhydrous
CH3CN (10 mL), and CsF (0.14 g, 0.9 mmol) afforded 6c as a
white solid, which was purified by column chromatography [eluent:
hexanes/ethyl acetate 1:1 (v/v), Rf = 0.70] and recrystallized from
chloroform/n-pentane; 0.09 g, 66%; white prisms; m.p. 187–189 °C.
1H NMR (400 MHz, CDCl3, 25 °C): δ = 3.30 (s, 3 H, OCH3), 6.22
1
3
3
(d, JP,C = 8.0 Hz, C-3), 118.34 (C-4Ј), 127.07 (C-3Ј), 127.11 (d,
1JP,C = 89.7 Hz, C-i), 128.7 (d, JP,C = 12.5 Hz, C-m), 130.26 (C-
3
2
4
2Ј), 131.3 (d, JP,C = 10.1 Hz, C-o), 131.83 (d, JP,C = 1.7 Hz, C-p),
2
132.86 (d, JP,C = 11.9 Hz, C-6), 133.9 (C-4), 153.15 (C-1Ј), 158.25
(d, JP,C = 6.8 Hz, C-2) ppm. 31P{1H} NMR (202.456 MHz, [D8]-
2
THF, –30 °C): δ = 11.09 ppm.
3
4
3
(dd, JH,H = 8.1 Hz, JP,H = 4.7 Hz, 1 H, Ar H), 6.93 (dd, JH,H
=
General Procedure for the Preparation of the 2-(Arylamino)phenyl-
phosphane Oxides 6a–6c and the Phosphonate 6d: A solution of 2
(0.39 mmol) in anhydrous CH3CN (5 mL) was added over 2 h to a
mixture of 1k–1m (0.3 mmol) and CsF (0.9 mmol) in anhydrous
CH3CN (10 mL) at 0 °C. The resulting mixture was stirred at 25 °C
for 24 h. The reaction mixture was then filtered through a short
pad of Celite to remove insoluble substances. After concentration
of the filtrate under vacuum, the residue was purified by
chromatography on silica and then recrystallized to afford 6.
4
3
8.5 Hz, JP,H = 4.2 Hz, 1 H, Ar H), 7.13 (d, JH,H = 8.8 Hz, 2 H,
Ar H), 7.25–7.29 (m, 1 H, Ar H), 7.37 (d, JH,H = 8.8 Hz, 2 H, Ar
3
H), 7.42–7.48 (m, 4 H, Ar H), 7.50–7.54 (m, 2 H, Ar H), 7.71–7.77
(m, 4 H, Ar H) ppm; NH not observed. 13C{1H} NMR (100 MHz,
1
CDCl3, 25 °C): δ = 54.77 (OCH3), 100.01 (d, JP,C = 103.2 Hz, C-
3
3
1), 101.15 (d, JP,C = 5.6 Hz, C-3), 108.30 (d, JP,C = 7.9 Hz, C-5),
3
114.89 (C-4Ј), 123.37 (C-2Ј), 128.13 (d, JP,C = 12.8 Hz, C-m),
131.56 (d, JP,C = 3.8 Hz, C-p), 131.59 (d, JP,C = 10.5 Hz, C-o),
132.09 (C-3Ј), 134.06 (d, JP,C = 107.6 Hz, C-i), 134.60 (C-4),
4
2
2
2
P-[2-(4-Methylphenylamino)phenyl]-P,P-diphenylphosphane Oxide
(6a): The general procedure with 1k (0.1 g, 0.3 mmol) in anhydrous
CH3CN (5 mL), 2a (0.12 g, 0.39 mmol) in anhydrous CH3CN
(10 mL), and CsF (0.14 g, 0.9 mmol) afforded 6a as a white solid,
which was purified by column chromatography [eluent: hexanes/
ethyl acetate 1:1 (v/v), Rf = 0.61] and recrystallized from chloro-
form/n-pentane; 0.1 g, 90 %; white prisms; m.p. 147–149 °C. 1H
NMR (400 MHz, CDCl3, 25 °C): δ = 2.28 (s, 3 H, CH3), 6.64–6.69
140.91 (C-1Ј), 152.37 (C-6), 161.75 (d, JP,C = 2.7 Hz, C-2) ppm.
31P{1H} NMR (162 MHz, CDCl3, 25 °C): δ = 38.75 ppm. IR (Nu-
jol): ν = 1583 (s), 1465 (vs), 1118 (m), 774 (s), 749 (s) cm–1. HRMS
˜
(ESI): calcd. for C25H22BrNO2P [M + H]+ 478.0566; found
478.0571.
Dimethyl 2-(4-Methylphenylamino)phenylphosphonate (6d): The ge-
neral procedure with 1l (0.07 g, 0.3 mmol) in anhydrous CH3CN
(5 mL), 2b (0.12 g, 0.39 mmol) in anhydrous CH3CN (10 mL), and
CsF (0.14 g, 0.9 mmol) afforded 7c as a white solid, which was
purified by column chromatography [eluent: hexanes/ethyl acetate
1:1 (v/v), Rf = 0.70] and recrystallized from chloroform/n-pentane;
3
3
4
(m, 1 H, Ar H), 6.85 (ddd, JP,H = 14.4 Hz, JH,H = 7.7 Hz, JH,H
3
= 1.4 Hz, 1 H, Ar H), 7.00 (d, JH,H = 8.4 Hz, 2 H, Ar H), 7.05
(d, JH,H = 8.4 Hz, 2 H, Ar H), 7.24–7.31 (m, 2 H, Ar H), 7.45–
3
7.49 (m, 4 H, Ar H), 7.52–7.58 (m, 2 H, Ar H), 7.64–7.71 (m, 4 H,
1
0.06 g, 66%; white prisms; m.p. 187–189 °C. H NMR (300 MHz,
Ar H), 8.71 (s, 1 H, NH) ppm. 13C{1H} NMR (100 MHz, CDCl3,
3
CDCl3, 25 °C): δ = 2.33 (s, 3 H, CH3), 3.78 (d, JP,H = 11.1 Hz, 6
1
25 °C): δ = 20.71 (CH3), 114.06 (d, JP,C = 104.5 Hz, C-1), 114.69
H, OCH3), 6.75–6.81 (m, 1 H, Ar H), 7.08–7.15 (m, 4 H, Ar H),
7.17–7.22 (m, 1 H, Ar H), 7.28–7.33 (m, 1 H, Ar H), 7.50 (ddd,
3
3
(d, JP,C = 7.7 Hz, C-3), 117.49 (d, JP,C = 12.9 Hz, C-5), 121.30
3
(C-2Ј), 128.44 (d, JP,C = 12.3 Hz, C-m), 129.62 (C-3Ј), 131.95 (d,
3
4
3JP,H = 14.7 Hz, JH,H = 7.8 Hz, JH,H = 1.2 Hz, 1 H, Ar H), 8.33
4JP,C = 2.9 Hz, C-p), 131.97 (d, JP,C = 9.9 Hz, C-o), 132.06 (C-4Ј),
2
(s, 1 H, NH) ppm. 13C{1H} NMR (75 MHz, CDCl3, 25 °C): δ =
20.85 (CH3), 52.79 (d, JP,C = 5.0 Hz, OCH3), 108.71 (d, JP,C
183.2 Hz, C-1), 114.36 (d, JP,C = 11.9 Hz, C-3), 117.83 (d, JP,C
1
4
132.11 (d, JP,C = 104.8 Hz, C-i), 133.13 (d, JP,C = 1.7 Hz, C-4),
2
1
=
=
3
2
133.66 (d, JP,C = 11.2 Hz, C-6), 138.64 (C-1Ј), 150.45 (d, JP,C
=
3
3
4.0 Hz, C-2) ppm. 31P{1H} NMR (162 MHz, CDCl3, 25 °C): δ =
14.0 Hz, C-5), 121.98 (C-2Ј), 129.92 (C-3Ј), 132.79 (C-4Ј), 133.54
(d, 2JP,C = 6.8 Hz, C-6), 133.99 (d, 4JP,C = 1.6 Hz, C-4), 138.57 (C-
1Ј), 149.52 (d, 2JP,C = 8.3 Hz, C-2) ppm. 31P{1H} NMR (162 MHz,
36.25 ppm. IR (Nujol): ν = 1591 (vs), 1571 (vs), 1450 (vs), 1118 (s),
˜
726 (vs), 694 (s) cm–1. HRMS (ESI): calcd. for C25H23NOP [M +
H]+ 384.1512; found 384.1518.
CDCl , 25 °C): δ = 24.45 ppm. IR (Nujol): ν = 1595 (vs), 1516 (vs),
˜
3
1455 (vs), 1139 (s), 1027 (vs), 823 (s), 790 (s) cm–1. HRMS (ESI):
calcd. for C15H19NO3P [M + H]+ 292.1097; found 292.1103.
P-[2-(4-Bromophenylamino)phenyl]-P,P-diphenylphosphane Oxide
(6b): The general procedure with 1l (0.12 g, 0.3 mmol) in anhydrous
CH3CN (5 mL), 2a (0.12 g, 0.39 mmol) in anhydrous CH3CN
(10 mL), and CsF (0.14 g, 0.9 mmol) afforded 6b as a white solid,
General Procedure for the Preparation of the Phosphonium Triflates
8: A solution of 2a (0.78 mmol) in anhydrous CH3CN (5 mL) was
1092
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2014, 1084–1095

π-Insertion Reactions of Benzynes into P=N and P=S Double Bonds
2
added over 2 h to a mixture of 7 (0.3 mmol) and CsF (0.9 mmol)
in anhydrous CH3CN (10 mL) at 0 °C. The resulting mixture was
stirred at 25 °C for 24 h. The reaction mixture was then filtered
through a short pad of Celite to remove insoluble substances. After
concentration of the filtrate under vacuum, the residue was purified
by flash column chromatography on silica and then recrystallized
to afford 6.
155 °C. 1H NMR (400 MHz, CDCl3, 25 °C): δ = 2.67 [d, JP,H
=
13.6 Hz, 6 H, P(CH3)2], 6.95–6.98 (m, 2 H, Ar H), 7.22–7.24 (m, 3
H, Ar H), 7.42–7.45 (m, 1 H, Ar H), 7.52–7.55 (m, 2 H, Ar H),
7.60–7.70 (m, 5 H, Ar H), 7.98–8.06 (m, 1 H, Ar H) ppm. 13C{1H}
1
NMR (75 MHz, CDCl3, 25 °C): δ = 10.33 (d, JP,C = 57.3 Hz,
1
1
CH3), 120.76 (q, JF,C = 320.4 Hz, CF3SO3), 121.86 (d, JP,C
=
88.6 Hz, C-i), 121.89 (d, 1JP,C = 91.5 Hz, C-1), 128.24 (C-4Ј), 129.47
3
3
(d, JP,C = 12.1 Hz, C-5), 129.78 (C-2Ј or C-3Ј), 130.12 (d, JP,C
=
P,P,P-Triphenyl-P-[2-(phenylthio)phenyl]phosphonium Triflate (8a):
The general procedure with 7a (0.09 g, 0.3 mmol) in anhydrous
CH3CN (5 mL), 2a (0.23 g, 0.78 mmol) in anhydrous CH3CN
(10 mL), and CsF (0.14 g, 0.9 mmol) afforded 8a as a white solid,
which was purified by flash column chromatography [gradient el-
uents: chloroform/methanol 9:1 (v/v) then ethanol; Rf = 0.19, TLC,
chloroform/methanol 9:1 (v/v)] and recrystallized from dichloro-
methane/diethyl ether; 0.13 g, 70%; white prisms; m.p. 140–142 °C.
2
12.1 Hz, C-m), 130.20 (C-2Ј or C-3Ј), 131.22 (d, JP,C = 11.0 Hz,
C-o), 133.50 (C-1Ј), 134.15 (d, 4JP,C = 3.0 Hz, C-p), 135.21 (d, 2JP,C
4
3
= 11.2 Hz, C-6), 135.76 (d, JP,C = 2.4 Hz, C-4), 135.92 (d, JP,C
=
8.6 Hz, C-3), 140.61 (d, JP,C = 7.1 Hz, C-2) ppm. 31P{1H} NMR
2
(162 MHz, CDCl3, 25 °C): δ = 21.01 ppm. 19F NMR (282 MHz,
CDCl , 25 °C): δ = –78.27 ppm. IR (Nujol): ν = 1440 (m), 1257
˜
3
(vs), 1155 (s), 1029 (s), 744 (s) cm–1. HRMS (ESI): calcd. for
C20H20PS [M –OTf]+ 323.1018; found 323.1024.
3
1H NMR (400 MHz, CDCl3, 25 °C): δ = 6.90 (d, JH,H = 7.6 Hz,
Supporting Information (see footnote on the first page of this arti-
cle): Detailed procedures for the synthesis of 1, characterization
2 H, Ar H), 7.19–7.28 (m, 3 H, Ar H), 7.29–7.33 (m, 1 H, Ar H),
7.50 (dd, 3JH,H = 8.0 Hz, 4JP,H = 5.2 Hz, 1 H, Ar H), 7.58 (td, 3JH,H
1
data and copies of the H, 13C{1H}, and 31P{1H} NMR spectra of
4
= 7.6 Hz, JP,H = 2.8 Hz, 1 H, Ar H), 7.65–7.78 (m, 13 H, Ar H),
7.81–7.84 (m, 3 H, Ar H) ppm. 13C{1H} NMR (100 MHz, CDCl3,
the new compounds.
1
1
25 °C): δ = 118.12 (d, JP,C = 90.8 Hz, C-i), 118.47 (d, JP,C
=
94.2 Hz, C-1), 120.71 (q, 1JF,C = 320.9 Hz, CF3SO3), 128.89 (C-4Ј),
129.16 (d, JP,C = 12.6 Hz, C-5), 129.79 (C-3Ј), 130.65 (d, JP,C
13.1 Hz, C-m), 131.00 (C-2Ј), 132.10 (C-1Ј), 134.17 (d, JP,C
10.3 Hz, C-o), 135.08 (d, JP,C = 8.7 Hz, C-3), 135.31 (d, JP,C
3
3
Acknowledgments
=
=
=
=
2
3
4
The authors wish to dedicate this article to Professor José Elguero
with respect and admiration. The authors thank the Ministerio de
Ciencia e Innovación (MICINN) and Fondos Europeos para el De-
sarrollo Regional (FEDER) (projects CTQ2008-05827/BQU and
CTQ2011-27705) and Fundación Séneca-CARM (project 08661/
PI/08) for the financial support of this research. R. R. also thanks
the University of Murcia for a fellowship.
4
2
3.0 Hz, C-p), 136.34 (d, JP,C = 2.6 Hz, C-4), 137.49 (d, JP,C
11.9 Hz, C-6), 143.46 (d, 2JP,C = 7.1 Hz, C-2) ppm. 31P{1H} NMR
(121 MHz, CDCl , 25 °C): δ = 22.01 ppm. IR (Nujol): ν = 1440
˜
3
(m), 1266 (vs), 1108 (m), 1030 (s), 731 (s), 691 (m) cm–1. HRMS
(ESI): calcd. for C30H24PS [M –OTf]+ 447.1331; found 447.1337.
P-Methyl-P,P-diphenyl-P-[2-(phenylthio)phenyl]phosphonium Tri-
flate (8b): The general procedure with 7b (0.07 g, 0.3 mmol) in an-
hydrous CH3CN (5 mL), 2a (0.23 g, 0.78 mmol) in anhydrous
CH3CN (10 mL), and CsF (0.14 g, 0.9 mmol) afforded 8b as a
white solid, which was purified by flash column chromatography
[gradient eluents: chloroform/methanol 9:1 (v/v) then ethanol; Rf =
0.17, TLC, chloroform/methanol 9:1 (v/v)] and recrystallized from
dichloromethane/diethyl ether; 0.14 g, 87%; white prisms; m.p.
147–149 °C. 1H NMR (400 MHz, CDCl3, 25 °C): δ = 3.09 (d, 2JP,H
= 13.2 Hz, 3 H, PCH3), 7.03–7.05 (m, 2 H, Ar H), 7.23–7.29 (m, 3
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3
4
H, Ar H), 7.32 (ddd, JP,H = 14.8 Hz, JH,H = 8.0 Hz, JH,H
=
1.2 Hz, 1 H, Ar H), 7.45–7.52 (m, 2 H, Ar H), 7.65–7.72 (m, 9 H,
Ar H), 7.74–7.78 (m, 2 H, Ar H) ppm. 13C{1H} NMR (100 MHz,
CDCl3, 25 °C): δ = 10.07 (d, 1JP,C = 58.8 Hz, CH3), 119.37 (d, 1JP,C
1
1
= 89.8 Hz, C-i), 120.74 (d, JP,C = 93.0 Hz, C-1), 120.84 (q, JF,C
3
= 320.8 Hz, CF3SO3), 128.52 (C-4Ј), 129.10 (d, JP,C = 12.6 Hz, C-
5), 129.86 (C-3Ј), 130.54 (d, JP,C = 12.9 Hz, C-m), 130.74 (C-2Ј),
132.85 (d, JP,C = 10.5 Hz, C-o), 133.05 (C-1Ј), 134.95 (d, JP,C
2.8 Hz, C-p), 135.74 (d, JP,C = 8.7 Hz, C-3), 135.95 (d, JP,C
3
2
4
=
=
=
3
4
2
2
2.3 Hz, C-4), 136.56 (d, JP,C = 12.0 Hz, C-6), 141.87 (d, JP,C
7.3 Hz, C-2) ppm. 31P{1H} NMR (162 MHz, CDCl3, 25 °C): δ =
21.69 ppm. IR (Nujol): ν = 1440 (m), 1263 (s), 1114 (m), 1030 (s),
˜
909 (s), 732 (vs) cm–1. HRMS (ESI): calcd. for C25H22PS [M –
OTf]+ 385.1174; found 385.1179.
P,P-Dimethyl-P-phenyl-P-[2-(phenylthio)phenyl]phosphonium Tri-
flate (8c): The general procedure with 7c (0.05 g, 0.3 mmol) in an-
hydrous CH3CN (5 mL), 2a (0.23 g, 0.78 mmol) in anhydrous
CH3CN (10 mL), and CsF (0.14 g, 0.9 mmol) afforded 8c as a
white solid, which was purified by flash column chromatography
[gradient eluents: chloroform/methanol 9:1 (v/v) then ethanol; Rf =
0.17, TLC, chloroform/methanol 9:1 (v/v)] and recrystallized from
dichloromethane/diethyl ether; 0.1 g, 73%; white prisms; m.p. 153–
Eur. J. Org. Chem. 2014, 1084–1095
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1093

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Received: September 30, 2013
Published Online: January 1, 2014
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