Preparation, structure, and chemistry of phosphorane-derived phenyliodonium sulfonates

Article abstract of DOI:10.1016/S0040-4039(02)00275-7

New triphenylphosphorane-derived phenyliodonium triflates and tosylates were prepared by the reaction of the appropriate iodosobenzene sulfonate with stabilized phosphonium ylides. Structure of the triflate derivative was determined by a single-crystal X-

Full text of DOI:10.1016/S0040-4039(02)00275-7

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 43 (2002) 2359–2361
Preparation, structure, and chemistry of phosphorane-derived
phenyliodonium sulfonates
Viktor V. Zhdankin,a,* Olena Maydanovych,a Jon Herschbach,a Jessica Bruno,a Elena D. Matveevab
and Nikolai S. Zefirovb
aDepartment of Chemistry, University of Minnesota Duluth, Duluth, MN 55812, USA
bDepartment of Chemistry, Moscow State University, Moscow 119899, Russia
Received 22 January 2002; revised 7 February 2002; accepted 8 February 2002
Abstract—New triphenylphosphorane-derived phenyliodonium triflates and tosylates were prepared by the reaction of the
appropriate iodosobenzene sulfonate with stabilized phosphonium ylides. Structure of the triflate derivative was determined by a
single-crystal X-ray analysis. These compounds represent a potentially useful class of reagents that combine in one molecule
synthetic advantages of a phosphonium ylide and an iodonium salt. © 2002 Elsevier Science Ltd. All rights reserved.
During the last few years the chemistry of hypervalent
iodine compounds (l3-iodanes) has experienced an
unprecedented growth.1 A broad variety of polyvalent
iodine reagents have been prepared and new, highly
useful synthetic procedures have been developed. Iodo-
nium salts and ylides represent an especially important
class of iodanes with rich and synthetically useful chem-
istry.1,2 Mixed phosphonium–iodonium ylides, which
are best described by the resonance contributors 1a and
1b, represent a potentially interesting, but underinvesti-
gated, class of l3-iodanes combining in one molecule
synthetic advantages of phosphonium ylides and iodo-
nium salts. Several examples of the tetrafluoroborate
derivatives 1 (X=BF4) were previously prepared by the
reaction of phosphonium ylides with (diace-
toxyiodo)benzene in the presence of HBF4,3 but their
chemistry was not elaborated.
phonium ylides 2 with the pyridinium complex of
iodobenzene ditriflate (3)4 under mild conditions.5 It
should be emphasized that the use of the pyridinium
complex 3 is essential in this procedure; the application
of PhIO/Tf2O leads to the formation of a black tar due
to the strongly acidic character of this reagent. The
tosylate derivatives 6 can be conveniently prepared
under similar conditions by treatment of phosphonium
ylides 2 with Koser reagent6 in dichloromethane
(Scheme 1). Products 6 were isolated in the form of
stable, white, microcrystalline solids; the yields and
melting points of compounds 4 and 6 are listed in Table
1.
Sulfonates 4 and 6 were identified by NMR, IR, and
elemental analysis.5 In particular, proton NMR spectra
of these compounds showed signals of four phenyls as
well as the respective signals of the R-group and the
tosylate anion for products 6. 13C NMR displays the
signal of the ylidic carbon at 118–119 ppm as well as
the signals corresponding to the aromatic rings and the
R-groups.
In this communication we report the preparation and
structure of new sulfonate derivatives of phosphonium–
iodonium ylides. We have found that the triflate iodo-
nium derivatives 4 can be prepared as microcrystalline,
off-white solids in good yields by the reaction of phos-
The structure of iodonium triflate 4a was unambigu-
ously established by a single-crystal X-ray analysis.†
The cationic portion of molecule 4a is shown in Fig. 1.
† Crystallographic data (excluding structure factors) for structure 4a
have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication number CCDC 177487.
Copies of the data can be obtained, free of charge, on application
to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44
1223 336033 or e-mail: deposit@ccdc.cam.ac.uk).
Keywords: iodonium; phosphonium; hypervalent iodine; X-ray crys-
tallography.
* Corresponding author. Tel.: (218) 726-6902; fax: (218) 726-7394;
e-mail: vzhdanki@d.umn.edu
0040-4039/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)00275-7

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V. V. Zhdankin et al. / Tetrahedron Letters 43 (2002) 2359–2361
ular interaction with the carbonyl oxygen (P1ꢀO1=
,
,
2.849 A). The C1ꢀC2 bond distance of 1.415 A
indicates a significant double bond character, which is
consistent with the enolic structure 7 and typical of the
carbonyl stabilized phosphonium ylides. In agreement
with the enolic structure 7, the atoms I1, P1, C3, O1,
C1 and C2 are located in the same plane, while the
phenyl of the iodonium group and the triflate group are
outside of this plane. Structure 4a is in good agreement
with the X-ray data on the related tetrafluoroborate
derivative published in 1984 by Moriarty and co-
workers.3
Scheme 1. Preparation of phosphonium–iodonium sulfonates.
Table 1. Yields and melting points of phosphonium–iodo-
nium sulfonates
Product
R
Yield (%)
Mp (°C)
4a
4b
4c
4d
6a
6b
6c
C(O)CH3
CO2CH3
CN
83
89
78
56
50
47
51
108–110
131–132
Oil
129
110–111
118
CHO
C(O)CH3
CO2CH3
CN
102–107
A preliminary investigation of chemical properties of
compounds 4 and 6 has demonstrated that they react
with soft nucleophiles, such as the thiophenolate anion,
to afford products 8, which can be further converted to
alkenes 9 by the Wittig reaction with benzaldehyde
(Scheme 2). In a representative example, the mixed
ylide 6a selectively reacts with lithium thiophenolate in
dichloromethane to afford the respective ylide 8a along
with iodobenzene as the by-product. Products 8 were
identified on the basis of NMR spectra and high-resolu-
tion FAB mass-spectrometry.7 The reaction of ylides 8
with benzaldehyde afforded alkenes 9 as a mixture of E
and Z isomers.
In conclusion, we report the preparation and X-ray
structure of new phosphanylidene-derived iodonium
salts. These compounds represent a potentially useful
class of reagents that combine in one molecule synthetic
advantages of a phosphonium ylide and an iodonium
salt.
Figure 1. Perspective view of the cationic part of 4a. Selected
,
distances (A) and angles (°): IꢀC(1) 2.068(7), IꢀC(4) 2.108(6),
,
PꢀC(1) 1.749(7), PꢀC(10) 1.817(6), C(1)ꢀC(2) 1.415(10) A;
IꢀCꢀP 121.8(4), C(1)ꢀIꢀC(4) 101.4(3)°.
The structural data revealed a typical geometry of an
iodonium salt with a C1ꢀIꢀC4 bond angle of 101.4° and
the triflate anion weakly associated with the iodine
,
atom. The IꢀC bond distances of 2.068 and 2.108 A are
within the range of a typical bond length in diaryliodo-
1
,
nium salts (2.0–2.1 A). The distance between the iodine
atom and the nearest oxygen of the triflate anion,
,
I···OTf, is 2.957 A, while the shortest P···OTf distance is
,
4.370 A, indicating the absence of secondary bonding
between the phosphorus atom and the triflate anion.
Scheme 2. Reactions of mixed phosphonium–iodonium ylides
The phosphorus atom has a relatively short intramolec-
with thiophenolate anion.

V. V. Zhdankin et al. / Tetrahedron Letters 43 (2002) 2359–2361
2361
Acknowledgements
from dichloromethane/diethyl ether afforded 0.556 g (83%)
of product 4a in the form of a white, microcrystalline
solid; mp 108–110°C; IR (KBr): 3065, 1534, 1440, 1252,
1
512 cm−1; H NMR (CDCl3): l 7.27–7.66 (m, 20H, 4Ph),
This work was supported by a research grant from the
National Science Foundation (NSF/CHE-0101021) and
by a CRDF award RC2-2216. Special thanks are made
to Dr. Victor G. Young, Jr. and the X-ray Crystallo-
graphic Laboratory of the University of Minnesota for
X-ray structural analysis of compound 4a.
2.62 (s, 3H, CH3). 13C NMR (CDCl3): l 193.4 (CꢁO),
134–122 (4Ph), 121 (q, JCF=318 Hz, OTf), 118 (d, JCP
=
104 Hz, CꢁP), 27 (CH3). Anal. calcd for C28H23F3IO4PS:
C, 50.16; H, 3.46; I, 18.93; S, 4.78. Found: C, 49.72; H,
3.48; I, 19.01; S, 4.65%. FAB HRMS m/z 521.0504 (M−
OTf)+, calcd for C28H23F3IO4PS 521.05.
Preparation of 6a: A mixture of reagent 56 (0.196 mg, 0.5
mmol) and phosphonium ylide 2a (0.151 g, 0.5 mmol) in
dry dichloromethane was stirred overnight at room tem-
perature under nitrogen. The resulting solution was con-
centrated in vacuum yielding a slightly yellow oil. The oil
was recrystallized from dichloromethane and diethyl ester
to afford 0.170 g (50%) of product 6a as white crystals, mp
110–111°C; IR (KBr): 3050, 1550, 1223, 1176, 1114, 1031
References
1. (a) Varvoglis, A. The Organic Chemistry of Polycoordi-
nated Iodine; VCH Publishers: New York, 1992; (b) Var-
voglis, A. Hypervalent Iodine in Organic Synthesis;
Academic Press: London, 1997; (c) Stang, P. J.; Zhdankin,
V. V. Chem. Rev. 1996, 96, 1123–1178.
2. Pirkuliev, N. S.; Brel, V. K.; Zefirov, N. S. Russ. Chem.
1
cm−1; H NMR (CDCl3): l 7.4–8.0 (m, 20H), 7.34 (d, 2H,
Rev. 2000, 69, 105–120.
3. Moriarty, R. M.; Prakash, I.; Prakash, O.; Freeman, W.
A. J. Am. Chem. Soc. 1984, 106, 6082.
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5. Representative experimental data. Preparation of 4a: A
solution of ylide 2a (0.106 g, 0.335 mmol) in 3 ml
dichloromethane was added to a suspension of triflate 34
(0.221 g, 0.335 mmol) under a nitrogen atmosphere at
room temperature. The solution was additionally stirred
for 3 h, washed several times with water, dried, and
concentrated in vacuum. Recrystallization of the residue
J=8 Hz), 7.12 (d, 2H, J=8 Hz) 2.63 (s, 3H), 2.33 (s, 3H);
13C NMR (CDCl3): 190.0, 135–122 (4Ph and Ts), 119.0 (d,
J
CP=90 Hz), 22.9, 16.8. Anal. calcd for C34H30IO4PS: C,
58.97; H, 4.37; I, 18.32. Found C, 59.05; H, 4.34; I,
18.45%.
6. Koser, G. F. Aldrichim. Acta 2001, 34, 89.
7. Product 8a: Oil, 1H NMR (CDCl3): l 7.0–7.8 (m, 20H,
4Ph), 2.35 (s, 3H, CH3). 13C NMR (CDCl3): l 196.8
(CꢁO), 143–124 (4Ph), 55.5 (d, JCP=104.4 Hz, CꢁP), 25.5
(CH3). FAB HRMS m/z 427.13188 (M+H)+, calcd for
C27H24OPS 427.12855.