A new class of iodonium ylides engineered as soluble primary oxo and nitrene sources [8]

Full text of DOI:10.1021/ja991094j

7164
J. Am. Chem. Soc. 1999, 121, 7164-7165
Scheme 1
A New Class of Iodonium Ylides Engineered as
Soluble Primary Oxo and Nitrene Sources
Dainius Macikenas,† Ewa Skrzypczak-Jankun,‡ and
John D. Protasiewicz*,†
Department of Chemistry, Case Western ReserVe UniVersity
CleVeland, Ohio 44106-7078
Department of Chemistry, UniVersity of Toledo
Toledo, Ohio 43606-3390
ReceiVed April 7, 1999
Transition metal catalyzed atom and group transfer reactions
are important tools in both Nature’s and the synthetic chemist’s
arsenal for the assembly of functionalized molecules. Iodosyl-
benzene (PhIO) has served as a critical primary oxygen atom
source in many synthetic and biomimetic studies.1 The emergence
of (tosyliminoiodo)benzene2 (PhINTs, Ts ) p-toluenesulfonyl),
a nitrene analogue of iodosylbenzene, has allowed parallel
development of new classes of powerful catalytic imination and
aziridination reactions.3 These two iodonium ylides are popular
due to their effectiveness, relative ease of preparation, and rather
innocuous byproduct PhI.4 Catalytic reactions that employ these
reagents are heterogeneous due to their insoluble nature,5 and
efforts to improve catalytic performance or to gain mechanistic
insights are hindered. Systematic studies of the structures of PhIO
and ArINSO2Ar′ reveal extensive networks of I‚‚‚O and I‚‚‚N
secondary bonds and highly aggregated polymeric networks.6,7
We initially reasoned that disruption of these intermolecular
electrostatic forces could be achieved by the addition of external
materials having large dipoles, such as trimethylamine-N-oxide.
Although PhINTs can be readily solubilized by Me3NO in CDCl3,
a drop in the activity of PhINTs occurs.8 New iodonium ylides
ArIX (X ) O or NTs) having strong internal dipoles have thus
been engineered for introducing intramolecular I‚‚‚O secondary
bonds to replace intermolecular I‚‚‚N and I‚‚‚O secondary bonds.
These highly reactive primary oxo and tosylimino sources display
impressive solubility in organic media. In addition, single-crystal
X-ray analysis of the primary tosylimino source reveals several
fascinating structural features.
The synthesis of the organoiodine(III) species is outlined in
Scheme 1. Oxidation of 19 with peracetic acid leads to the
(diacetoxyiodo)arene 2. For maximal and most expedient yields
of the target ylides, 2 is used without purification or workup.
The corresponding pale yellow (tosyliminoiodo)arene (3) and
bright yellow iodosylarene (4) are thus obtained in 78 and 95%
yields (based on 1), respectively.10 The solution properties of 3
and 4 are quite remarkable. Compound 3, for example, will readily
dissolve in chloroform (ca. 0.14 M at room temperature, at least
a 50-fold increase over PhINTs), dichloromethane, and acetoni-
trile. The impressive solubility properties of 3 are exhibited, albeit
to a lesser extent, in the corresponding iodosylarene 4. Solutions
of up to 0.08 M in 4 can be obtained in CHCl3. Solutions of 3 in
CDCl3 show little signs of decomposition during a 20 h period
(<8%), thereby demonstrating the remarkable ability of the
internal I‚‚‚O secondary bond to stabilize the low-coordinate
hypervalent iodine atom. Such results are significant in that many
reactions utilizing PhINTs are plagued by hydrolytic side reac-
tions.11 13C{1H} NMR spectra of 3 and 4 in CDCl3 display
resonances shifted downfield for the ipso aromatic carbon atoms
at 115.5 and 117.9 ppm relative to 1 (δ 94.6) that clearly signal
oxidation to I(III).12
Single crystals of 3 suitable for X-ray structural analysis have
been grown from acetonitrile and the resulting details are
presented in Figure 1.13 Several features are noteworthy. First, 3
is loosely associated into centrosymmetric dimers by long-range
intermolecular I‚‚‚N and I‚‚‚O bonds (>3.0 Å), quite unlike the
infinite polymeric chains adopted in the solid state for PhIO and
PhINTs. Second, as anticipated, one of the sulfonyl oxygen atoms
† Case Western Reserve University.
‡ University of Toledo.
(1) Some examples and reviews: (a) Collman, J. P.; Zhang, X.; Lee, V.
J.; Uffelman, E. S.; Brauman, J. I. Science 1993, 261, 1404-1411. (b) Ojima,
I. Catalytic Asymmetric Synthesis; VCH Publishers: New York, 1993. (c)
Holm, R. H. Chem. ReV. 1987, 87, 1401-1449. (d) Holm, R. H.; Donahue,
J. P. Polyhedron 1993, 12, 571-589. (e) Noyori, R. Asymmetric Catalysis in
Organic Synthesis; Wiley: New York, 1994. (f) Pecoraro, V. L. Manganese
Redox Enzymes; VCH Publishers: New York, 1992. (g) Barton, D. H. R.;
Martell, A. E.; Sawyer, D. T. The ActiVation of Dioxygen and Homogeneous
Catalytic Oxidation; Plenum Press: New York, 1993.
(9) Compound 1 was prepared in two steps from PhStBu in 96% overall
yield. See: (a) Ipatieff, V. N.; Pines, H.; Friedman, B. S. J. Am. Chem. Soc.
1938, 60, 2731-2734. (b) Iwao, M.; Iihama, T.; Mahalanabis, K. K.; Perrier,
H.; Snieckus, V. J. Org. Chem. 1989, 54, 24-26. (c) Clayden, J.; Cooney, J.
J. A.; Julia, M. J. Chem. Soc., Perkin Trans. 1 1995, 7-14.
1
(10) Compound 3: Mp 148-149 °C dec. H NMR (CDCl3, 200 MHz) δ
(2) Yamada, Y.; Yamamoto, T.; Okawara, M. Chem. Lett. 1975, 361-
362.
(3) (a) Osborn, H. M. I.; Sweeney, J. Tetrahedron Asym. 1997, 8, 1693-
1715. (b) Johannsen, M.; Jørgensen, K. A. Chem. ReV. 1998, 98, 1689-1708.
(c) Lautens, M.; Klute, W.; Tam, W. Chem. ReV. 1996, 96, 49-92. (d) Tanner,
D. Angew. Chem., Int. Ed. Engl. 1994, 33, 599-619.
8.35 (d, J ) 8.2 Hz, 1H), 7.78-7.93 (m, 4H), 7.66-7.75 (m, 1H), 7.23 (d, J
) 8.2 Hz, 2H), 2.39 (s, 3H), 1.45 (s, 9H). 13C{1H} NMR (CDCl3, 75.5 MHz)
δ 142.1, 140.7, 136.2, 133.5, 132.1, 130.7, 129.4, 128.7, 126.8, 115.5, 63.6,
23.5, 21.4. Anal. Calcd for C17H20INO4S2: C, 41.38; H, 4.09; N, 2.84.
Found: C, 41.10; H, 4.00; N, 2.69. Compound 4: Mp 126 °C dec. 1H NMR
(CDCl3, 300 MHz) δ 8.09 (m, 1H), 7.88 (m, 2H), 7.66 (m, 1H), 1.39 (s, 9H).
13C{1H} NMR (CDCl3, 75.5 MHz) δ 135.4, 132.7, 132.0, 129.7, 127.2, 117.9,
63.3, 23.5. Anal. Calcd for C10H13IO3S: C, 35.31; H, 3.85. Found: C, 34.93;
H, 4.10.
(4) (a) Varvoglis, A. HyperValent Iodine in Organic Synthesis; Academic
Press: New York, 1997. (b) Stang, P. J.; Zhdankin, V. V. Chem. ReV. 1996,
96, 1123-1178. (c) Varvoglis, A. The Organic Chemistry of Polycoordinated
Iodine; VCH: New York, 1992. (d) Koser, G. F. The Chemistry of the
Functional Groups, Supplement D; Patai, S., Rappoport, Z., Eds.; John Wiley
& Sons: New York, 1983; pp 721-811.
(11) This decreased sensitivity to water is analogous to the added stability
imparted by intramolecular secondary Bi‚‚‚N bonding in a bismuth tosylimide.
See: Ikegami, T.; Suzuki, H. Organometallics 1998, 17, 1013-1017.
(12) (a) Katritzky, A. R.; Gallos, J. K.; Durst, H. D. Magn. Reson. Chem.
1989, 27, 815-822. (b) Mishra, A. K.; Olmstead, M. M.; Ellison, J. J.; Power,
P. P. Inorg. Chem. 1995, 34, 3210-3214.
(13) Crystal data for 3, C17H20INO4S2: Monoclinic, P21/n, a ) 11.252(2)
Å, b ) 10.092(2) Å, c ) 17.430(4) Å, b ) 99.40(3)°, Z ) 4, Fcalc ) 1.678
g/cm3. 13338 reflections (5080 unique) collected at 293(1) K for a crystal of
0.16 × 0.08 × 0.06 mm3 using a Bruker SMART Platform with CCD 1K
detector and Mo radiation with graphite monochromator, 2Θ < 60°. Final
refinement for 287 parameters converged to R1 ) 0.0403 (3575 reflections
with I > 2σ(I)), and wR2 ) 0.0746 (all data).
(5) PhIO and PhINTs solvolyze in methanol. See: (a) Schardt, B. C.; Hill,
C. L. Inorg. Chem. 1983, 22, 1563-1565. (b) White, R. E. Inorg. Chem.
1987, 26, 3916-3919.
(6) Carmalt, C. J.; Crossley, J. G.; Knight, J. G.; Lightfoot, P.; Martin, A.;
Muldowney, M. P.; Norman, N. C.; Orpen, A. G. J. Chem. Soc., Chem.
Commun. 1994, 2367-2368.
(7) Boucher, M.; Macikenas, D.; Ren, T.; Protasiewicz, J. D. J. Am. Chem.
Soc. 1997, 119, 9366-9376.
(8) Macikenas, D.; Meprathu, B. V.; Protasiewicz, J. D. Tetrahedron Lett.
1998, 39, 191-194.
10.1021/ja991094j CCC: $18.00 © 1999 American Chemical Society
Published on Web 07/16/1999

Communications to the Editor
J. Am. Chem. Soc., Vol. 121, No. 30, 1999 7165
Scheme 2
Figure 1. Structural diagram for compound 3. Selected bond distances
(Å) and angles (deg): I-N, 1.982(3); I-C8, 2.145(3); I‚‚‚O4, 2.677(3);
I‚‚‚N′, 3.105(3); I‚‚‚O2′, 3.550(3); S1-N, 1.629(3); S1-O1, 1.446(3);
S1-O2, 1.440(3); S2-O3, 1.437(2); S2-O4, 1.455(2); N-I‚‚‚O4,
170.92(9); C8-I‚‚‚O4, 73.3(1); C8-I-N, 97.9(1).
catalyst (eq 1).
2ArIO f ArI + ArIO2
(1)
Indeed, increasing the ratio of styrene to 4 to 20:1 from 5:1
increases the amount of epoxide formed (51%) and reduces the
quantity of 5 formed. The manganese-catalyzed disproportionation
of 4 is rapid (and quantitative) in the absence of olefin. In the
absence of catalyst the disproportionation of 4 is slow (t1/2 ∼ 6 h
in CDCl3). Disproportionation of iodosylbenzene has been previ-
ously noted and it has been predicted that an iodosylarene
solubilized by introducing substituents would be increasingly
susceptible to disproportionation unless steric effects could inhibit
disproportionation.18,19
The new soluble iodonium ylides presented here are expected
to lend added flexibility to catalytic atom and group transfers by
offering homogeneous conditions, to provide opportunities to
conduct studies at reduced temperatures, and to facilitate the
search of new catalysts for atom and group transfer reactions by
combinatorial methods.20 We are currently also exploring means
for the incorporation of chiral dipole groups into these ylides.21
forms a short intramolecular I‚‚‚O secondary bond to the
hypervalent iodine atom with a I‚‚‚O bond length of 2.667(3) Å.
Third, the nitrogen atom of the NTs group is located essentially
in the plane of the iodoarene ring trans to the sulfonyl oxygen
atom of the sulfone moiety (O2). The NSO2Ar′ group in all
previous structurally characterized ArINSO2Ar′ is located above
the plane of the iodoarene ring, presumably a result of steric
interactions between the NSO2Ar′ group and the ortho proton of
the iodoarene ring.7 The strength of the intramolecular I‚‚‚O bond
seems sufficient to overcome this interaction and thus 3 resembles
a number of cyclic λ3-iodinanes.4
Initial assessment of the ability of 3 and 4 as primary sources
of oxygen atoms and tosylimino groups is summarized in Scheme
2. Compound 3 and 4 react rapidly with tertiary phosphines and
thioethers and afford the corresponding products of oxo and
tosylimino transfer.14 Copper-catalyzed aziridination of styrene
and trans-stilbene by 3 proceeds efficiently for both substrates.15
Iodosylarene 4 is also effective for the manganese-catalyzed
epoxidations of styrene and stilbene.16 For example, the epoxi-
dation of styrene by 4 catalyzed by [Mn(salen)OAc] produced
the expected epoxide in 31% yield. This reaction, however, is
also accompanied by a considerable amount of a precipitate that
we have identified as the iodoxyarene 5.17 The iodoxyarene results
from a competitive disproportionation of the iodosylarene by the
Acknowledgment. We thank the CWRU Department of Chemistry
and the donors of the Petroleum Research Fund, administered by the
American Chemical Society, for support of this work, and we also thank
the Ohio Board of Reagents for financial support of the Ohio Crystal-
lography Consortium.
Supporting Information Available: Experimental details and char-
acterization of 1-4 and tables of crystal data, structure solution and
refinement, atomic coordinates, bond lengths, and angles for 3 (PDF).
This material is available free of charge via the Internet at http://pubs.acs.org.
JA991094J
(14) For details and related references see Supporting Information.
(15) (a) L ) 2, 2′-isopropylidenebis[(4S)-4-tert-butyl-2-oxazoline]. (b)
Evans, D. A.; Faul, M. M.; Bilodeau, M. T. J. Am. Chem. Soc. 1994, 116,
2742-2753.
(18) Nappa, M. J.; Tolman, C. A. Inorg. Chem. 1985, 24, 4711-4719.
(19) Bressan, M.; Morvillo, A. Inorg. Chem. 1989, 28, 950-953.
(20) Francis, M. B.; Jacobsen, E. N. Angew. Chem., Int. Ed. Engl. 1999,
38, 937-941.
(21) Recent exciting work has established that introduction of chiral dialkyl
ether groups (for secondary bonding to I(III) center) into analogues of Koser’s
reagent ([PhI(OH)(OTs)]) can promote asymmetric oxytosylation reactions.
See: (a) Hirt, U. H.; Spingler, B.; Wirth, T. J. Org. Chem. 1998, 63, 7674-
7679. (b) Wirth, T.; Hirt, U. H. Tetrahedron Asym. 1997, 8, 23-26.
(16) Zhang, W.; Loebach, J. L.; Wilson, S. R.; Jacobsen, E. N. J. Am.
Chem. Soc. 1990, 112, 2801-2803.
1
(17) Compound 5: Mp 160-165 dec. H NMR (DMSO-d6, 300 MHz) δ
8.46 (m, 1H), 8.13 (m, 1H), 7.96 (m, 1H), 7.87 (m, 1H), 1.32 (s, 9H). 13C{1H}
NMR (DMSO-d6, 75.5 MHz) δ 23.2, 61.2, 124.0, 131.2, 132.0 (this signal
splits into two signals in a DMSO-d6/benzene-d6 mixture), 135.0, 148.0.