Synthesis, crystal structure, and thermolysis of a pentacoordinate 1,2λ6-oxathietane: An intermediate of the Corey-Chaykovsky reaction of oxosulfonium ylides?

Full text of DOI:10.1021/ja953533u

J. Am. Chem. Soc. 1996, 118, 697-698
697
Scheme 1
Synthesis, Crystal Structure, and Thermolysis of a
Pentacoordinate 1,2λ6-Oxathietane: An
Intermediate of the Corey-Chaykovsky Reaction of
Oxosulfonium Ylides?
Fumihiko Ohno, Takayuki Kawashima,* and Renji Okazaki*
Department of Chemistry, Graduate School of Science
The UniVersity of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan
oxathietanes 3a and 3b, respectively (Scheme 1).6 Although
the 3,4,4-triphenyl derivative 3a was observed spectroscopically,
its isolation was unsuccessful because of its instability, while
the 3-phenyl-4,4-bis(trifluoromethyl) derivative 3b could be
purified by flash column chromatography (18%) with a recovery
of 1b (17%).7 Recrystallization of 3b from ether gave colorless
plates which melted at 139.5-141.1 °C with decomposition.
In the 1H NMR spectrum of 3b, the proton ortho to sulfur of
the Martin ligand5a,8 resonated at a low field (δ 8.70), which is
one of the features of compounds with a trigonal bipyramidal
(TBP) structure.2a,c,d,3,9 A downfield shift from 1b (δ 6.39) to
3b (δ 6.87) was observed for the methine proton on the four-
membered ring. In the 13C NMR spectra downfield shifts from
1b (δCH 87.66, δipso-C 136.63) to 3b (δCH 100.76, δipso-C 140.23)
were observed for the methine carbon and the ipso-carbon
adjacent to the central sulfur. These downfield shifts seem
attributable to the increased electropositivity of the central sulfur
of 3b compared with 1b.
The X-ray crystallographic analysis of 1b (Figure 1) and 3b
(Figure 2)10 indicated that they have distorted TBP structures
which are very similar to each other. The two oxygen atoms
of the oxathietane ring and the Martin ligand occupy the apical
positions, while two carbon atoms and a lone pair (for 1b) or
an exocyclic oxygen atom (for 3b) occupy the equatorial
positions. The phenyl group at the 3-position is cis to the lone
pair of sulfur (for 1b) or to the ecxocyclic oxygen (for 3b),
indicating that the oxidation of sulfurane 1b proceeds with
retention of configuration. The apical S-O bonds are bent away
from the lone pair (1b) or the equatorial oxygen (3b), leading
to the deviation of the O-S-O angles by 10.75(9)° and
18.6(3)° from linearity for 1b and 3b, respectively. The large
deviation in the range 10-20° is a common structural feature
of the hypervalent species containing a four-membered ring.2,3
The equatorial S-O bond length of 3b (1.445(6) Å) is similar
to that of sulfurane oxide 4 (1.439(4) Å), considerably shorter
than that of sulfoxides.5b The oxathietane ring of 1b is slightly
ReceiVed October 23, 1995
Oxetanes bearing highly coordinate main group elements at
the position adjacent to the oxygen atom have been well-known
as intermediates or transition states of very important reactions
in organic synthesis such as the Wittig and Peterson reactions.1
In our research on such oxetanes, we have synthesized penta-
coordinate 1,2-oxaphosphetanes,2a,b 1,2-oxasiletanide,2c 1,2-
oxagermetanide,2d and 1,2-oxastannetanide,2e i.e., intermediates
of the Wittig and Peterson-type reactions. We recently found
that tetracoordinate 1,2λ4-oxathietane 1a3a 1,2λ4-oxaselenetane
2,3b which have structures similar to those of the above group
14 and 15 element analogues, yielded no olefins on heating.
Specifically, in the case of 1a, bearing a tetracoordinate sulfur,
a small amount of an oxirane was observed in the reaction
mixture. This unique result prompted us to examine the
reactivity of such oxetanes bearing a pentacoordinate sulfur
which can be regarded as an intermediate of the Corey-
Chaykovsky reaction4 of oxosulfonium ylides with carbonyl
compounds. We now report on the synthesis, crystal structure,
and thermolysis of the first example of stable pentacoordinate
1,2λ6-oxathietane 3b, a novel type of sulfurane oxide.5
Oxidation of tetracoordinate 1,2λ4-oxathietanes 1a and 1b3a
with mCPBA in the presence of Na2HPO4 (CH2Cl2, 0 °C f 25
°C, 12 h) gave the corresponding pentacoordinate 1,2λ6-
(1) For the Wittig reactions, see: (a) Smith, D. J. H. In ComprehensiVe
Organic Chemistry; Barton, D. H. R., Ollis, W. D., Eds.; Pergamon: Oxford,
1979; Vol. 2, pp 1316-1329. (b) Maryanoff, B. E.; Reitz, A. B. Chem.
ReV. 1989, 89, 863-927. For the Peterson reactions, see: (c) Weber, W.
P. Silicon Reagents for Organic Synthesis; Springer-Verlag: New York,
1983; pp 58-73. (d) Ager, D. J. Org. React. (N.Y.) 1990, 38, 1-223. For
the Peterson-type reactions, see: (e) Kauffmann, T. Angew. Chem., Int.
Ed. Engl. 1982, 21, 410-429. (f) Pereyre, M.; Quintard, J.-P.; Rahm, A.
Tin in Organic Synthesis; Butterworths: London, 1987; pp 176-177.
(2) (a) Kawashima, T.; Kato, K.; Okazaki, R. J. Am. Chem. Soc. 1992,
114, 4008-4110. Kawashima, T.; Kato, K.; Okazaki, R. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 869-870. (b) Kawashima, T.; Takami, H.; Okazaki,
R. J. Am. Chem. Soc. 1994, 116, 4509-4510. (c) Kawashima, T.; Iwama,
N.; Okazaki, R. Ibid. 1992, 114, 7598-7599. (d) Kawashima, T.;
Nishiwaki, Y.; Okazaki, R. J. Organomet. Chem. 1995, 499, 143-146. (e)
Kawashima, T.; Iwama, N.; Okazaki, R. J. Am. Chem. Soc. 1993, 115,
2507-2508.
(6) Use of some other oxidizing reagents such as RuO4, ozone, and
dimethyldioxirane was unsuccessful.
(7) A complex reaction mixture including some unidentified products
was obtained. 3b: colorless plates, mp 139.5-141.1 °C dec; 1H NMR
(CDCl3, 500 MHz) δ 6.87 (s, 1H), 7.43-7.55 (m, 3H), 7.73 (d, J ) 7.5
Hz, 2H), 7.83 (d, J ) 7.8 Hz, 1H), 7.89 (t, J ) 7.8 Hz, 1H), 7.93 (t, J )
7.8 Hz, 1H), 8.70 (d, J ) 7.8 Hz, 1H); 13C{1H} NMR (CDCl3, 126 MHz)
δ 74.91 (sept, 2JCF ) 32 Hz), 80.74 (sept, 2JCF ) 32 Hz), 100.76 (s), 120.98
(q, 1JCF ) 287 Hz), 121.16 (q, 1JCF ) 287 Hz), 121.61 (q, 1JCF ) 287 Hz),
1
122.26 (q, JCF ) 288 Hz), 125.97 (s), 127.26 (s), 128.89 (s), 129.29 (s),
130.19 (m), 130.59 (s), 131.12 (s), 133.14 (s), 136.58 (s), 140.23 (s). Anal.
Calcd for C19H10F12O3S: C, 41.77; H, 1.84; S, 5.87. Found: C, 41.70; H,
2.08; S, 6.35.
(8) This bidentate ligand is very effective in stabilizing the higher
coordination states of nonmetallic elements; see: Perozzi, E. F.; Michalak,
R. S.; Figuly, G. D.; Stevenson, W. H., III; Dess, D. B.; Ross, M. R.; Martin,
J. C. J. Org. Chem. 1981, 46, 1049-1053.
(3) (a) Kawashima, T.; Ohno, F.; Okazaki, R. Angew. Chem., Int. Ed.
Engl. 1994, 33, 2094-2095. (b) Kawashima, T.; Ohno, F.; Okazaki, R. J.
Am. Chem. Soc. 1993, 115, 10434-10435.
(4) For the Corey-Chaykovsky reactions, see: (a) Aube´, J. In Compre-
hensiVe Organic Synthesis: SelectiVity, Strategy, and Efficiency in Modern
Synthetic Chemistry; Trost, B. M., Fleming, I., Eds.; Pergamon: Oxford,
1991; Vol. 1, pp 822-825. For the related reactions of aminosulfoxonium
ylides, see: (b) Johnson, C. R. Acc. Chem. Res. 1973, 6, 341-347.
(5) For previous examples of sulfurane oxides, see: (a) Martin, J. C.;
Perrozi, E. F. J. Am. Chem. Soc. 1974, 96, 3155-3168. (b) Perrozi, E. F.;
Martin, J. C.; Paul, I. C. Ibid. 1974, 96, 6735-6744. (c) Lau, P. H. W.;
Martin, J. C. Ibid. 1977, 99, 5490-5491. (d) Rongione, J. C.; Martin, J.
C. Ibid. 1990, 112, 1637-1638.
(9) Granoth, I.; Martin, J. C. J. Am. Chem. Soc. 1981, 103, 2711-2715.
(10) 1b: C19H10F12O2S, FW ) 530.33, crystal dimensions (mm) 0.50
× 0.50 × 0.30, orthorhombic, space group Pbca, a ) 18.096(2) Å, b )
19.682(2) Å, c ) 11.329(3) Å, V ) 4034(1) Å3, Z ) 8, Dcalcd ) 1.746
g/cm3, R ) 0.044, (Rw ) 0.026). 3b: C19H10F12O3S, FW ) 546.33, crystal
dimensions (mm) 0.50 × 0.20 × 0.30, monoclinic, space group P21/c, a )
10.522(7) Å, b ) 17.045(5) Å, c ) 12.491(5) Å, â ) 106.91(3)°, V )
2143(1) Å3, Z ) 4, Dcalcd ) 1.693 g/cm3, R ) 0.075, (Rw ) 0.049). Full
details of the crystallographic structure analyses are described in the
supporting information.
0002-7863/96/1518-0697$12.00/0 © 1996 American Chemical Society

698 J. Am. Chem. Soc., Vol. 118, No. 3, 1996
Communications to the Editor
Scheme 2a
a (a) CDCl3, 100 °C, 100 min. (b) CDCl3, 155 °C, 29 h.
Scheme 3
Figure 1. ORTEP drawing of 1b with thermal ellipsoid plot (30%
probability for all non-hydrogen atoms). Selected bond lengths (Å),
bond angles (deg), and dihedral angles (deg): S1-O1, 1.901(2); S1-
O2, 1.781(2); S1-C1, 1.859(3); S1-C11, 1.789(3); C1-C2,
1.548(4); C2-O1, 1.394(3); O1-S1-O2, 169.25(9); C1-S1-O1,
73.1(1); S1-C1-C2, 90.1(2); C1-C2-O1, 99.0(2); S1-O1-C2,
93.3(2); O2-S1-C11, 88.3(1); C1-S1-C11, 105.1(1); S1-C1-C2-
O1, 17.9(2); O1-S1-C1-C2, -13.5(2).
leaving group than the corresponding cyclic sulfenate, it can
be reasonably explained that oxirane formation readily occurs
in the case of 3b (Scheme 3), while a 1,3-proton shift11 followed
by a Pummerer rearrangement is favored in the case of 1b.
Although the oxetanes containing a pentacoordinate group
14 or 15 element gave an olefin,2 the oxathietane 3b having a
pentacoordinate sulfur yielded an oxirane. This indicates that
the thermal reactivity mainly depends on the bond energy of
the oxygen and the central atom. The oxathietane 3b can be
regarded as an equivalent to a syn-betaine which is formed by
the syn addition of the polarized C-sS+ bond of an oxosulfo-
nium ylide to the CdO bond of a carbonyl compound. The
relative facility of the syn addition compared with the anti
addition can be expected in terms of electrophilic assistance at
the oxygen center in the course of the Corey-Chaykovsky
reaction.12 Therefore, oxirane formation from 3b strongly
suggests a possibility that pentacoordinate 1,2λ6-oxathietanes
are intermediates in the addition step of the Corey-Chaykovsky
reaction.
Figure 2. ORTEP drawing of 3b with thermal ellipsoid plot (30%
probability for all non-hydrogen atoms). Selected bond lengths (Å),
bond angles (deg), and dihedral angles (deg): S1-O1, 1.445(6); S1-
O2, 1.822(7); S1-O3, 1.744(7); S1-C1, 1.852(8); S1-C11, 1.77(1);
C1-C2, 1.57(1); C2-O2, 1.40(1); O2-S1-O3, 161.4(3); C1-S1-
O2, 74.8(4); S1-C1-C2, 90.2(6); C1-C2-O2, 97.4(8); S1-O2-C2,
96.9(6); O3-S1-C11, 88.2(5); C1-S1-C11, 121.4(4); O1-S1-C1,
121.2(4); O1-S1-C11, 117.0(4); O1-S1-O2, 97.6(4); O1-S1-O3,
98.8(4); S1-C1-C2-O2, 6.8(7); O2-S1-C1-C2, -5.4(6).
Acknowledgment. This work was partially supported by a Kurata
Research Grant (T.K.) and a Grant-in-Aid for General Scientific
Research (B) No. 05453062 (T.K.) from the Ministry of Education,
Science and Culture, Japan. We are grateful to Associate Prof. N.
Tokitoh of the University of Tokyo for the determination of the X-ray
structures of 1b and 3b. We also thank Central Glass, Shin-etsu
Chemical, and Toso Akzo Co. Ltd. for the gifts of organofluorine
compounds, trialkylsilanes, and alkyllithiums, respectively.
puckered (S-C-C-O 17.9(2)°), while that of 3b is almost
planar (S-C-C-O 6.8(7)°).
Supporting Information Available: Physical and spectral data for
1b, 3a,b, 5, 6, and 7, an experimental procedure for the synthesis of
3b, and X-ray crystallographic data with tables of thermal and positional
parameters, bond lengths, and bond angles for 1b and 3b (27 pages).
This material is contained in many libraries on microfiche, immediately
follows this article in the microfilm version of the journal, can be
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Thermolysis (CDCl3, 100 °C, 100 min in a degassed sealed
tube) of 3b gave oxirane 5 (85%) and cyclic sulfinate 6 (97%).
The mild conditions and simplicity in the thermolysis products
are in marked contrast to those of tetracoordinate 1,2λ4-
oxachalcogenetanes.3 The thermolysis (CDCl3, 155 °C, 29 h)
of 1b afforded a somewhat complicated mixture of cyclic
thioacetal 7 (84%), 8 (11%), and hexafluoroacetone (9) (8%)
(Scheme 2).
JA953533U
These results have revealed an interesting difference in
reactivity between oxetanes with a tetracoordinate sulfur and
those with a pentacoordinate sulfur. In both cases, the first step
of the reaction can be considered to be the S-O bond cleavage
of the four-membered rings. Since cyclic sulfinate 6 is a better
(11) A similar 1,3-proton shift was observed in the thermolysis of 2.3b
(12) A theoretical study has reported that there is no activation energy
for the syn addition, while there is a 10.6 kcal/mol barrier for the anti
addition in the case of sulfonium ylide H2SdCH2 with formaldehyde; see:
Volatron, F.; Eisenstein, O. J. Am. Chem. Soc. 1987, 109, 1-14.