Synthesis, crystal structure, and thermolysis of the first tetracoordinate 1λ4,2-selenazetidines: Aziridine formation reaction from a four-membered heterocycle bearing highly coordinate selenium

Article abstract of DOI:10.1021/ol007015m

Equation presented The first tetracoordinate 1λ⁴,2-selenazetidines were synthesized by taking advantage of the Martin ligand and characterized by X-ray crystallographic analysis. The selenazetidines gave the corresponding aziridine and the cyclic selenenate on their thermolysis, which indicates the possibiliy that a highly coordinate 1,2-heterachalcogenetane may provide the corresponding heteracyclopropane regardless of the heteroatoms.

Full text of DOI:10.1021/ol007015m

ORGANIC
LETTERS
2001
Vol. 3, No. 5
691-694
Synthesis, Crystal Structure, and
Thermolysis of the First Tetracoordinate
1λ4,2-Selenazetidines: Aziridine
Formation Reaction from a
Four-Membered Heterocycle Bearing
Highly Coordinate Selenium
Naokazu Kano, Yuya Daicho, Nobuhito Nakanishi, and Takayuki Kawashima*
Department of Chemistry, Graduate School of Science, The UniVersity of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
takayuki@chem.s.u-tokyo.ac.jp
Received December 18, 2000
ABSTRACT
The first tetracoordinate 1λ4,2-selenazetidines were synthesized by taking advantage of the Martin ligand and characterized by X-ray
crystallographic analysis. The selenazetidines gave the corresponding aziridine and the cyclic selenenate on their thermolysis, which indicates
the possibility that a highly coordinate 1,2-heterachalcogenetane may provide the corresponding heteracyclopropane regardless of the
heteroatoms.
Oxetanes bearing highly coordinate heavier main-group
elements at the neighboring position of oxygen have been
known as intermediates or transition states of very important
reactions in organic synthesis such as the Wittig reaction
and Peterson-type reactions.1 In the course of our study on
the heteracyclobutanes, we previously reported the olefin
formation reactions of such oxetanes bearing highly coor-
dinate group 13, 14, and 15 elements.2,3 Furthermore, we
also reported the synthesis of 1,2-azaphosphetidines 1,4
nitrogen versions of oxaphosphetanes,3 which undergo the
olefin extrusion on their thermolysis (Figure 1). Contrary to
such heteracyclobutanes, we found that pentacoordinate 1,2-
(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) Gosney, I.; Rowley, A. G. In Organo-
phosphorus Reagents in Organic Synthesis; Cadogan, J. I. G., Ed.; Academic
Press: New York, 1979; pp 17-153. (c) Maryanoff, B. E.; Reitz, A. B.
Chem. ReV. 1989, 89, 863-927. (d) Vedejs, E.; Peterson, M. J. Top.
Stereochem. 1994, 20, 1-157. For the Peterson reactions, see: (e) Colvin,
E. W. Silicon in Organic Synthesis; Butterworth: London, 1981; pp 141-
152. (f) Ager, D. J. Synthesis 1984, 384-398. (g) Ager, D. J. Org. React.
(N.Y.) 1990, 38, 1-223. For the Peterson-type reactions, see: (h) Kauff-
mann, T. Top. Curr. Chem. 1980, 92, 109-147. (i) Kauffmann, T. Angew.
Chem., Int. Ed. Engl. 1982, 21, 410-429. (j) Pereyre, M.; Quitard, J.-P.;
Rahm, A. Tin in Organic Synthesis; Butterworth: London, 1987; pp 176-
177.
Figure 1.
10.1021/ol007015m CCC: $20.00 © 2001 American Chemical Society
Published on Web 02/16/2001

oxathietanes 2 and tetracoordinate 1,2-oxaselenetanes 3 do
not give the corresponding olefins.5,6 Moreover, oxachalco-
genetanes 2 and 3b, which bear phenyl groups at the
3-positions, extruded the corresponding oxiranes.5b,6b These
reactions giving the corresponding three-membered ring
compounds on their thermolysis are expected to proceed for
other heteracyclobutanes, e.g., a 1,2-selenazetidine with
highly coordinate chalcogen atoms. However, there has been
no report on the compounds with such a ring system. We
herein describe the synthesis of tetracoordinate 1,2-selen-
azetidines by taking advantage of the Martin ligand,7 together
with the crystal structure and thermolysis.
of two diastereomers of tetracoordinate 1,2-selenazetidines
7a and 7b. The chromatography of the mixture afforded 7a
(40%) and 7b (8%) separately as stable colorless crystals.
In the 19F NMR spectra of 7a and 7b (xylene-d10), four
sets of quartets for the trifluoromethyl groups derived from
the HFIA unit and the Martin ligand unit were observed due
to their nonequivalence consistent with the ring formation.
Downfield shifts of the 77Se resonance (CDCl3) in going from
6 (δ 435.1) to 7a (δ 713.0) and 7b (δ 759.5), respectively,
are consistent with tetracoordinate selenurane structures.8,9
1
In the H NMR spectra (CDCl3) of 7a and 7b, the ortho
proton of the “Martin ligand” resonated at low field (δ 7.96
and 8.08, respectively), which is a typical feature of
compounds with a trigonal-bipyramidal (TBP) or a pseudo-
TBP structure bearing a polar apical bond.10 These spectro-
scopic features support their structures as tetracoordinate 1,2-
selenazetidines.
Sequential treatment of benzyl selenide 46b with lithium
diisopropylamide (LDA), (hexafluoroisopropylidene)aniline
(HFIA), and an aqueous solution of NH4Cl gave â-amino-
alkyl selenide 5 (Scheme 1). The oxidation of â-aminoalkyl
The X-ray crystallographic analysis of 7a revealed its
distorted pseudo-TBP structure at a selenium atom (Figure
2).11,12 Oxygen and nitrogen atoms occupied two apical
positions, whereas two carbon atoms as well as the lone pair
occupied three equatorial positions. This is the first example
of the synthesis and structural analysis of a 1,2-selenazetidine.
Scheme 1a
a LDA, THF, -78 °C, 2 h; (b) PhNdC(CF3)2, THF, -78 °C, 10
h; (c) aqueous NH4Cl; (d) n-Bu4NF, THF, 0 °C, 30 min; (e)
mCPBA, CHCl3, 0 °C, 30 min; (f) chromatography (SiO2, hexane/
benzene 3/1).
selenide 6, which was quantitatively obtained by the de-
silylation of 5 with n-Bu4NF, with mCPBA gave a mixture
(2) (a) Kawashima, T.; Okazaki, R. Synlett 1996, 600-608. (b) Ka-
washima, T.; Okazaki, R. In AdVances in Strained and Interesting Organic
Molecules; Halton, B., Ed.; JAI Press Inc.: Stamford, 1999; Vol. 7, pp
1-41. (c) Kawashima, T. J. Organomet. Chem. 2000, 611, 256-263.
(3) (a) Kawashima, T.; Kato, K.; Okazaki, R. J. Am. Chem. Soc. 1992,
114, 4008-4010. (b) Kawashima, T.; Kato, K.; Okazaki, R. J. Am. Chem.
Soc. 1998, 120, 6848-6848. (c) Kawashima, T.; Kato, K.; Okazaki, R.
Angew. Chem., Int. Ed. Engl. 1993, 32, 869-870. (d) Kawashima, T.;
Watanabe, K.; Okazaki, R. Tetrahedron Lett. 1997, 38, 551-554. (e)
Kawashima, T.; Okazaki, R.; Okazaki, R. Angew. Chem., Int. Ed. Engl.
1997, 36, 2500-2502.
(4) Kawashima, T.; Soda, T.; Okazaki, R.; Angew. Chem., Int. Ed. Engl.
1996, 35, 1096-1098.
(5) (a) Ohno, F.; Kawashima, T.; Okazaki, R. J. Am. Chem. Soc. 1996,
118, 697-698. (b) Kawashima, T.; Ohno, F.; Okazaki, R.; Ikeda, H.;
Inagaki, S. J. Am. Chem. Soc. 1996, 118, 12455-12456.
Figure 2. ORTEP drawing of 7a with thermal ellipsoid plot (30%
probability). Selected bond lengths [Å], angles [deg], and torsion
angles [deg] for 7a: Se1-N1, 1.974(2); Se1-C1, 1.991(2); Se1-
O1, 2.008(1); Se1-C3, 1.924(2); C1-C2, 1.566(3); C2-N1,
1.450(3); O1-Se1-N1, 158.70(7); C1-Se1-C3, 107.64(9); C1-
Se1-N1, 69.72(8); Se1-C1-C2, 91.0(1); C1-C2-N1, 97.4(2);
C2-N1-Se1, 95.2(1); Se1-N1-C2-C1, 21.9(1); Se1-C1-C2-
N1, 21.6(1).
(6) (a) Kawashima, T.; Ohno, F.; Okazaki, R. J. Am. Chem. Soc. 1993,
115, 10434-10435. (b) Ohno, F.; Kawashima, T.; Okazaki, R. Chem.
Commun. 1997, 1671-1672.
(7) A bidentate ligand, -C6H4C(CF3)2O-, developed by Martin for
stabilizing hypervalent species, see: (a) Martin, J. C.; Perozzi, E. F. Science
1976, 191, 154-159. (b) 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. (c) Martin, J. C. Science 1983, 221, 509-514.
692
Org. Lett., Vol. 3, No. 5, 2001

Interestingly, the nitrogen atom of 7a is not trigonal planar
in marked contrast to that of 1, which is isoelectronic to 7a,
though other structural features of 7a are almost the same
as those of 1 and 3a.4,6a Pyramidal configuration for the
nitrogen atom of 7a would emerge from the steric repulsion
between the Martin ligand and the phenyl group on the
nitrogen atom.
phosphorus analogue 1. This is the first finding for aziridine
formation pathways from heteracyclobutanes with highly
coordinate main-group elements. Compounds 10 and 11 are
most likely formed by the ring-opening reaction of aziridine
8, giving azomethine ylide 12, followed by the hydrolysis
of 12 with water in the reaction mixture, indicating that 10
and 11 are the secondary products of 8 (Scheme 3).
Consequently, the four-membered ring significantly devi-
ates from planarity as indicated by the torsion angle [Se1-
N1-C2-C1] of 7a [21.9(1)°]. The Se1-C1 bond length
[1.991(2) Å] is slightly longer than that of previously reported
oxaselenetanes 3a [1.923(7) Å].6a Taking into account the
standard deviations, other common bond lengths of the four-
membered ring are almost same as those of 1 and 3a.4,6a
The Se1-O1 and Se1-C3 bond lengths are also almost same
as those of 3a. The bond angle between two apical bonds
deviates by 21.30(7)° from 180°, probably due to its ring
strain. Such deviation was also observed for 1 and 3a.4,6a
Since the spectral features of both 7a and 7b are very similar,
7b should be another diastereomer of 1,2-selenazetidine in
regard to the configuration at the selenium, that is, the phenyl
group at 4-position in 7b is trans to that of the lone pair but
cis in 7a.
Scheme 3
The above experimental result shows that a 1,2-selen-
azetidine has a reactivity similar to that of 1,2-oxaselenetanes
3b at the point of giving the corresponding three-membered
ring compound on the thermolysis. Such ligand coupling
reactions on selenium would be favorable compared with
the olefin formation, because the energy gain obtained by
the formation of the double-bond between selenium and
oxygen or nitrogen is too small to be the driving force of
the latter reaction. We previously reported the possibility that
the 1,2-oxachalcogenetanes are intermediates of the Corey-
Chaykovsky reaction of chalcogenonium ylides with carbonyl
compounds.5,6b In addition, such an aziridine formation of a
sulfonium ylide with a cyclic imine was previously reported
as a nitrogen version of the Corey-Chaykovsky reaction.14
The result of thermolysis of 7a giving 8 indicates that a 1,2-
selenazetidine might be the intermediate of the selenium
version of this reaction.
Thermolysis of 7a at 210 °C in xylene-d10 was monitored
1
by H and 19F NMR spectroscopy (Scheme 2). The signals
Scheme 2
Similarly, thermolysis of 7b (xylene-d10, at 210 °C) also
gave 8 (79%), 9 (100%), 10 (15%), and 11 (16%) as final
products, but 7a was also observed during the reaction. The
thermal reaction of 7b at 150 °C gave predominantly 7a
(78%) with a small amount of 8 (13%) and 9 (13%) in 91%
conversion of the reaction (10 h), resulting in the formation
of 8, 9, 10, and 11 as the final products (225 h). These results
indicate that 7b isomerized to 7a before its thermolysis.
In summary, we have revealed an interesting difference
in reactivity between azetidines with group 15 elements and
those with group 16 elements. Hence, the above experimental
due to the corresponding aziridine 8 and cyclic selenenate 9
increased with the decrease in those of 7a. Finally, 8 (78%),
9 (100%), 10 (16%), and 11 (16%) were obtained after
complete consumption of 7a.13 No formation of the corre-
sponding olefin was observed, in sharp contrast to the
(11) A crystal data of 7a. C25H15F12NOSe, FW ) 652.34, colorless
crystals, monoclinic, space group P21/n, a ) 9.7010(2), b ) 15.3350(5),
and c ) 16.8410(5) Å, â ) 101.446(2)°, V ) 2455.5(1) Å3, Z ) 4, Fcalcd
) 1.764 g cm-3, T ) 150 K. Of the 4474 reflections which were collected,
4340 were unique. The structure was solved by direct methods and expanded
by using Fourier techniques. The final cycle of full-matrix least-squares
refinement on F2 was based on all 4340 observed reflections and 361
variable parameters and converged with unweighted and weighted agreement
factors of R1 ) 0.039 and wR2 ) 0.118.
(8) For reviews on the 77Se NMR, see: (a) Luthra, N. P.; Odom, J. D.
In The Chemistry of Organic Selenium and Tellurium Compounds; Patai,
S., Rappoport, Z., Eds.; John Wiley & Sons: New York, 1986; Vol. 1;
Chapter 6, pp 189-241. (b) Paulmier, C. Selenium Reagents and Intermedi-
ates in Organic Synthesis; Pergamon: Oxford, 1986; pp 17-21.
(9) For selenuranes with Se-N bond(s), see: (a) Roesky, H. W.;
Ambrosius, K. Z. Naturforsch. 1978, 33B, 759-762. (b) Fujihara, H.; Mima,
H.; Erata, T.; Furukawa, N. J. Chem. Soc., Chem. Commun. 1991, 98-99.
(c) Fujihara, H.; Mima, H.; Ikemori, M.; Furukawa, N. J. Am. Chem. Soc.
1991, 113, 6337-6338. (d) Fujihara, H.; Ueno, Y.; Chiu, J.-J.; Furukawa,
N. J. Chem. Soc., Perkin Trans. 1 1992, 2247-2248. (e) Fujihara, H.; Mima,
H.; Erata, T.; Furukawa, N. J. Am. Chem. Soc. 1993, 115, 9826-9827. (f)
Fujihara, H.; Mima, H.; Furukawa, N. Tetrahedron 1996, 52, 13951-13960.
(g) Mima, H.; Fujihara, H.; Furukawa, N. Tetrahedron 1998, 54, 743-
752.
(12) Crystallographic data for the structure reported in this paper have
been deposited with the Cambridge Crystallographic Data Centre as
supplementary publication no. CCDC-149505. Copies of the data can be
obtained free of charge on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK (fax (+44)1223-336-033; e-mail deposit@ccdc.cam.ac.uk).
(13) The yields of these products were determined on the basis of the
1
integral of H and 19F NMR spectra of the reaction solution.
(10) Granoth, I.; Martin, J. C. J. Am. Chem. Soc. 1979, 101, 4618-
4621.
(14) Hortmann, A. G.; Robertson, D. A. J. Am. Chem. Soc. 1967, 89,
5974-5975.
Org. Lett., Vol. 3, No. 5, 2001
693

results suggest that thermolysis of a highly coordinate 1,2-
heterachalcogenetane provides the corresponding hetera-
cyclopropane regardless of the heteroatom in contrast to the
group 15 analogues. The investigation on the stereochemistry
of the aziridine formation and its kinetic study are in
progress.
T.K.). We thank Central Glass, Shin-etsu Chemicals, and
Tosoh Akzo Co., Ltd. for the gifts of organofluorine
compounds, organosilicon compounds, and alkyllithiums,
respectively.
Supporting Information Available: Experimental pro-
cedure for the preparation of 5-7, spectral data for 5, 6, 7a,
7b, and 8, and crystal details of 7a. This material is available
free of charge via the Internet at http://pubs.acs.org.
Acknowledgment. This work was partially supported by
Grants-in-Aid for Scientific Research from the Ministry of
Education, Science, Sports and Culture of Japan (N.K. and
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