Synthesis and thermolysis of novel spiroselenuranes bearing two oxaselenetane rings: Double oxirane formation reactions from 1,5-dioxa-4λ4-selenaspiro[3.3]heptanes

Article abstract of DOI:10.1039/b009789f

The first stable spiroselenuranes bearing two oxaselenetane rings have been synthesized, characterized by X-ray crystallographic analysis, and shown to be thermally reactive giving two molar equivalents of the corresponding oxirane with elimination of ele

Full text of DOI:10.1039/b009789f

Synthesis and thermolysis of novel spiroselenuranes bearing two oxaselenetane
rings: double oxirane formation reactions from
1,5-dioxa-4l4-selenaspiro[3.3]heptanes†
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
113-0033, Japan. E-mail: takayuki@chem.s.u-tokyo.ac.jp
Received (in Cambridge, UK) 6th December 2000, Accepted 29th January 2001
First published as an Advance Article on the web 14th February 2001
The first stable spiroselenuranes bearing two oxaselenetane
rings have been synthesized, chracterized by X-ray crystallo-
graphic analysis, and shown to be thermally reactive giving
two molar equivalents of the corresponding oxirane with
elimination of elemental selenium, in sharp contrast to the
behavior of the phosphorus and silicon analogues.
generated hexafluoroacetone (HFA), and then with aqueous
NH4Cl gave mono(b-hydroxyalkyl) selenide 6 (28%) (Scheme
1). A diastereomer mixture of bis(b-hydroxyalkyl) selenides 7
was obtained from 6 by repetition of the same procedure as the
addition of HFA to 5 (2.0 equiv. of LDA and 3.0 equiv. of
HFA). Separation by flash column chromatography (SiO2) gave
dl-7 (7%) and meso-7 (61%). Oxidative cyclization of dl-7 and
meso-7 with Br2 in the presence of Et3N afforded the corre-
In the course of our study on oxetanes containing high-
coordinate main group elements at the position adjacent to the
oxygen atom,1 we have reported the syntheses and isolation of
intermediates of Wittig- and Peterson-type olefin formation
reactions.2,3 For the purpose of elucidating the influence of ring
size of the spiro-ring system on the reactivity of the hetera-
cyclobutanes, we have investigated the synthesis and reactivity
4
sponding tetracoordinate 1,5-dioxa-4l -selenaspiro[3.3]hep-
tanes trans-trans-8 (30%) and trans-cis-8 (49%), respectively.
Recrystallization of trans-trans-8 and trans-cis-8 from hexane–
diethyl ether gave colorless plates which melted at 93.5–108.4
and 105.0–106.2 °C with decomposition, respectively.§
In the 1H, 13C and 19F NMR spectra of trans-trans-8, the two
oxetane rings were observed equivalently, whereas those of
trans-cis-8 were non-equivalent. Downfield shifts from dl-7 (dH
4.98, dC 52.31) to trans-trans-8 (dH 6.35, dC 88.07) were
observed for the proton and carbon of the methine adjacent to
the central selenium, which is a common spectral feature for
tetracoordinate 1,2-oxachalcogenetanes.1,6 In the 77Se NMR
spectra of trans-trans-8 (dSe 835.3) and trans-cis-8 (dSe 882.0)
were observed multiplets due to the long-range coupling with
19F nuclei. The large downfield shifts in dSe from 7 [dSe 521.1
(dl), 521.7 (meso)] to 8 and their similar chemical shifts to
compounds 4 (4a: dSe 781; 4b: dSe 793; 4c: dSe 840.8) strongly
support the selenurane structure for 8. We have also synthesized
trans-trans-9 with two phenyl groups instead of two phenylthio
groups of trans-trans-8.¶
X-Ray crystallographic analysis indicated that the asym-
metric unit of a crystal of trans-trans-9 contains one and a half
molecules, A and B, the latter of which is disordered in two
different orientations on the crystallographic inversion center.∑
Both molecules have a distorted pseudo-trigonal bipyramidal
(TBP) structure with two oxygen atoms at apical positions and
two carbon atoms and a lone pair at equatorial positions. The
of compounds 1 and 2, which have two oxaphosphetane and
oxasiletane rings, respectively, and found that 1 undergoes
double olefin extrusion,4 while 2 undergoes homo-Brook
rearrangement to give the corresponding alcohol.5 On the other
hand, we have recently found that the oxirane formation
6
reactions from pentacoordinate 1,2l -oxathietanes 3a,b or
4
tetracoordinate 1,2l -oxaselenetanes 4a,b proceed with reten-
tion of configuration,6 which is the first example for the oxirane
formation without backside attack of oxide anion on the carbon
attached to the chalcogen atom, in sharp contrast to the Corey–
Chaykovsky reaction.7 These results prompted us to study
4
tetracoordinate 1,5-dioxa-4l -selenaspiro[3.3]heptanes, a novel
type of a spiroselenurane bearing two oxaselenetane rings. We
now report, for the first time, their synthesis and unique thermal
behavior.
Sequential treatment of (PhSCH2)2Se 5 with 1.1 equiv. of
lithium diisopropylamide (LDA), with 2.0 equiv. of freshly
† Electronic supplementary information (ESI) available: full experimental
details and spectroscopic data. See http://www.rsc.org/suppdata/cc/b0/
b009789f
‡ Present address: Department of Chemical and Biological Sciences,
Faculty of Science, Japan Women’s University, 2-8-1 Mejirodai, Bunkyo-
ku, Tokyo 112-8681, Japan.
Scheme 1 Reagents and conditions: i, 1.1 equiv. of LDA, THF, 278 °C, 10
min; ii, 2.0 equiv. of (CF3)2CNO, –78 °C, 30 min; iii, aqueous NH4Cl; iv, 2.0
equiv. of LDA, THF, –78 °C, 10 min; v, 3.0 equiv. of (CF3)2CNO, –78 °C,
30 min; vi, 1.1 eq Br2, 8.3 equiv. of Et3N, CCl4, 0 °C, 30 min.
DOI: 10.1039/b009789f
Chem. Commun., 2001, 463–464
This journal is © The Royal Society of Chemistry 2001
463

Although oxetanes containing a pentacoordinate group 14 or
15 element give rise to olefins,1a spiro oxachalcogenetanes
yielded oxiranes, regardless of the ring size (five- or four-
membered ring). This indicates that the thermal reactivity
mainly depends on the bond energy of the oxygen and the
central atom. Investigation of the stereochemistry of the oxirane
formation is now in progress.
This work was partially supported by Grants-in-Aid for
Scientific Research on Priority Areas No. 09239101 and
General Scientific Research (B) No. 10440212 (T. K.) from the
Ministry of Education, Science, Sports and Culture, Japan. We
are grateful to Professor N. Tokitoh of Kyoto University for the
determination of the X-ray structure of trans-trans-9. We also
thank Central Glass, Shin-etsu Chemical, and Toso Akzo Co.
Ltd. for the gifts of organofluorine compounds, trialkylsilanes
and alkyllithiums, respectively.
Fig. 1 ORTEP drawing of trans-trans-9 with thermal ellipsoid plot (30%
probability for all non-hydrogen atoms). Selected bond lengths (Å), bond
angles (°) and torsion angles (°): Se1–O1 1.971(4), Se1–O2 1.955(4), Se1–
C1 1.979(6), Se1–C3 1.978(6), C1–C2 1.532(8), C2–O1 1.388(6), C3–C4
1.531(8), O2–C4 1.392(7); O1–Se1–O2 155.26(18), C1–Se1–O1 71.1(2),
Se1–C1–C2 90.0(4), C1–C2–O1 103.7(5), Se1–O1–C2 94.7(3), C1–Se1–
C3 109.2(3), O2–Se1–C3 71.9(2), O2–C4–C3 104.3(5), Se1–C3–C4
89.1(4); Se1–C1–C2–O1 25.9(5), Se1–C3–C4–O2 26.1(5).
Notes and references
§ Selected data: for trans-trans-8: colorless plates (hexane–Et2O); mp
93.5–108.4 °C (decomp.); 1H NMR (C6D6, 500 MHz) d 6.35 (s, 2H, SeCH),
6.86–6.95 (m, 6H), 7.43–7.46 (m, 4H); 19F NMR (C6D6, 254 MHz) d –74.0
(q, 4JFF = 8.3 Hz, 6F), 278.7 (q, 4JFF 8.3 Hz, 6F); 77Se NMR (CDCl3, 51.5
MHz) d 835.3 (m). HRMS (70 eV): m/z calc. for C20H12F12O2S280Se
655.9252, found 655.9263. For trans-trans-9: colorless plates (hexane–
Et2O); mp 178.2–179.8 °C (decomp.); 1H NMR (CDCl3, 500 MHz) d 6.86
(s, 2H, SeCH), 7.40 (d, 3J 7.2 Hz, 4H), 7.45–7.53 (m, 6H); 19F NMR
(CDCl3, 254 MHz) d 273.4 (q, 4JFF 9.0 Hz, 6F), –78.2 (q, 4JFF 9.0 Hz, 6F);
77Se NMR (CDCl3, 51.5 MHz) d 723.1 (s). HRMS (70 eV): m/z calc. for
C20H12F12O280Se 591.9811, found 591.9816. Satisfactory 13C NMR spectra
were obtained for both trans-trans-8 and trans-trans-9.
ORTEP drawing of molecule A (Fig. 1) shows that both the
phenyl groups at the 3- and 3A-positions are cis to the lone pair
of selenium and trans to the Se–C bond of another four-
membered ring. The apical Se–O bonds are bent away from the
lone pair leading to the deviation of the O–Se–O angle by
22.74(18)° from linearity, which is a common structural feature
of the hypervalent species containing a four-membered
ring.1,4,6a The apical Se–O bond lengths [1.971(4) and 1.955(4)
Å)] are between those [1.977(4) and 1.902(4) Å] of selenurane
4c.1b The two oxaselenetane rings of trans-trans-9 are almost
planar [Se–C–C–O; 26.2195(10)° and 26.5439(10)°] similar
to 4c [Se–C–C–O 4.7(4)°].1b
¶ Synthesis of trans-trans-9 is described in the supporting information
(ESI†).
∑ Crystal data for trans-trans-9: C20H12F12O2Se, M = 591.25, monoclinic,
space group P21/n, a = 9.621(2), b = 22.144(3), c = 16.221(2) Å, b =
106.209(4)°, U = 3318.3(9) Å3, T = 298 K, Z = 6, m(Mo-Ka) = 18.14
cm21, 8261 refelections measured, 7812 (Rint = 0.075) which were used in
all calculations. The final wR(F2) was 0.221 (all data). CCDC 154648. See
http://www.rsc.org/suppdata/cc/b0/b009789f/ for crystallographic data in
.cif or other electronic format.
Thermolyses of trans-trans-8 (C6D6, 120 °C, 11 h) and trans-
cis-8 (C6D6, 60 °C, 19 h) in a degassed sealed tube gave oxirane
10 in 72 and 83% yields,** respectively, with black precipitates
and minor unidentified products, indicating that both com-
pounds underwent double oxirane extrusion reaction. The
formation of elemental selenium (black precipitates) was
confirmed by observation of the signal due to tris(dimethylami-
no)phosphine selenide (dP 84.9) after treatment of the reaction
mixture with tris(dimethylamino)phosphine (dP 121.5). On the
other hand, the thermolysis of trans-trans-9 (CD3C6D5, 200 °C,
12 d) gave a somewhat complicated mixture containing oxirane
11 (31%) and deuterated alcohol 12 (19%). (Scheme 2)** The
formation of 12 indicates that radical species were generated by
homolytic bond cleavage, probably because drastic conditions
were necessary for the thermolysis.
** The yields were calculated assuming that 1 mol of 8 or 9 gives 2 mol of
products.
1 (a) T. Kawashima and R. Okazaki, Synlett, 1996, 600; T. Kawashima and
R. Okazaki, in Advances in Strained and Interesting Organic Molecules,
ed. B. Halton, JAI Press Inc., Stamford, 1999, vol. 7, pp. 1–41; (b) T.
Kawashima, F. Ohno and R. Okazaki, J. Am. Chem. Soc., 1993, 115,
10 434.
2 For the Wittig reactions, see: D. J. H. Smith, in Comprehensive Organic
Chemistry, ed. D. H. R. Barton and W. D. Ollis, Pergamon, Oxford, 1979,
vol. 2, pp. 1316–1329; B. E. Maryanoff and A. B. Reitz, Chem. Rev.,
1989, 89, 863; E. Vedejs and M. J. Peterson, Top. Stereochem., 1994, 21,
1.
3 For the Peterson reactions, see: W. P. Weber, Silicon Reagents for
Organic Synthesis, Springer-Verlag, New York, 1983, pp. 58–73; D. J.
Ager, Org. React. (New York), 1990, 38, 1.
4 T. Kawashima, R. Okazaki and R. Okazaki, Angew. Chem., Int. Ed. Engl.,
1997, 36, 2500.
5 T. Kawashima, K. Naganuma and R. Okazaki, Organometallics, 1998,
17, 367.
6 (a) T. Kawashima, F. Ohno, R. Okazaki, H. Ikeda and S. Inagaki, J. Am.
Chem. Soc., 1996, 118, 12455; (b) F. Ohno, T. Kawashima and R.
Okazaki, Chem. Commun., 1997, 1671.
7 For the Corey–Chaykovsky reactions, see: J. Aubé, in Comprehensive
Organic Synthesis: Selectivity, Strategy, and Efficiency in Modern
Synthetic Chemistry, ed. B. M. Trost and I. Fleming, Pergamon, Oxford,
1991, vol. 1, pp. 822–825.
Scheme 2
464
Chem. Commun., 2001, 463–464