Synthesis of four- and five-membered heterocycles derived from an iminophosphorane

Article abstract of DOI:10.1080/10426500212297

Reactions of an iminophosphorane bearing the Martin ligand with a ketone, an isothiocyanate, and an alkyne gave the corresponding cycloadducts, 1,3,2λ⁵-oxazaphosphetidine, 1,3,2λ⁵-diazaphosphetidine-4-thione, and 1,2λ⁵-azaphosphetine, respectively, while that with dimethyl acetylenedicarboxylate (DMAD) and successive hydrolysis afforded the 1,2λ⁵-oxaphosphole-(2H)-one. Thermal reactions of the cycloadducts were also studied.

Full text of DOI:10.1080/10426500212297

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Phosphorus, Sulfur, and Silicon and the Related
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Synthesis of Four- and Five-Membered Heterocycles
Derived from an Iminophosphorane
Naokazu Kano a , Jia-Hua Xing a , Azusa Kikuchi a , Seiji Kawa a & Takayuki Kawashima a
a Department of Chemistry, Graduate School of Science , The University of Tokyo , Tokyo,
Japan
Published online: 27 Oct 2010.
To cite this article: Naokazu Kano , Jia-Hua Xing , Azusa Kikuchi , Seiji Kawa & Takayuki Kawashima (2002) Synthesis of
Four- and Five-Membered Heterocycles Derived from an Iminophosphorane, Phosphorus, Sulfur, and Silicon and the Related
Elements, 177:6-7, 1685-1687, DOI: 10.1080/10426500212297
To link to this article: http://dx.doi.org/10.1080/10426500212297
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Phosphorus, Sulfur and Silicon, 2002, Vol. 177:1685–1687
C
Copyright 2002 Taylor & Francis
1042-6507/02 $12.00 + .00
DOI: 10.1080/10426500290092875
SYNTHESIS OF FOUR- AND FIVE-MEMBERED
HETEROCYCLES DERIVED FROM AN
IMINOPHOSPHORANE
Naokazu Kano, Jia-Hua Xing, Azusa Kikuchi, Seiji Kawa,
and Takayuki Kawashima
Department of Chemistry, Graduate School of Science,
The University of Tokyo, Tokyo, Japan
(Received August 3, 2001; accepted December 25, 2001)
Reactions of an iminophosphorane bearing the Martin ligand with a
ketone, an isothiocyanate, and an alkyne gave the corresponding cy-
cloadducts, 1,3,2 5-oxazaphosphetidine, 1,3,2 5-diazaphosphetidine-
4-thione, and 1,2 5-azaphosphetine, respectively, while that with
dimethyl acetylenedicarboxylate (DMAD) and successive hydrolysis af-
forded the 1,2 5-oxaphosphole-(2H)-one. Thermal reactions of the cy-
cloadducts were also studied.
Keywords: Cycloaddition; heterocycles; iminophosphorane; phospho-
rane; thermolysis; x-ray analysis
There has been much interest in the chemistry of four-membered het-
erocycles containing both a pentacoordinate phosphorus atom and other
heteroatom(s) in view of their unique structures and reactivities.1 In the
course of our study on such heteracyclobutanes, we have achieved the
syntheses of 1,2 5-oxaphosphetanes2 and 1,2 5-azaphosphetidines,3
that is, the intermediates of Wittig reactions, by taking advantage
of the Martin ligand. On the other hand, an iminophosphorane, which
is a nitrogen analog of the phosphorus ylide, is expected to construct
a variety of four-membered ring compounds by the cycloaddition with
multiple bond compounds. We report here the syntheses and thermo-
lyses of novel heterocycles bearing a pentacoordinate phosphorus atom
derived from an iminophosphorane bearing the Martin ligand and a
2,4,6-triisopropylphenyl (denoted as Tip hereafter) group.
Address correspondence to Takayuki Kawashima, Department of Chemistry, Gradu-
ate 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
1685

1686
N. Kano et al.
SCHEME 1
RESULTS AND DISCUSSION
Reactions of iminophosphorane 1 with hexafluoroacetone 2, phenyl
isothiocyanate 3, and phenylethynyl trifluoromethyl sulfone 4 gave the
5
corresponding cycloadducts, 1,3,2 5-oxazaphosphetidine 5,4 1,3,2
-
diazaphosphetidine-4-thione 6, and 1,2 5-azaphosphetine 7, re-
spectively. Interestingly, successive treatment of 1 with dimethyl
acetylenedicarboxylate (DMAD) and water afforded not the corre-
sponding 1,2-azaphosphetine, but the 1,2 5-oxaphosphol-5(2H)-one 85
(Scheme 1). The structures of these products were established by x-ray
crystallographic analyses. It is worth mentioning that the oxygen ana-
log of 1,2-azaphosphetine, 1,2-oxaphosphete, is only an intermediate in
the reactions of phosphine oxides and DMAD.6
The thermolysis of the four-membered ring compound 5 revealed the
formation of the Wittig-type products, the corresponding imine 9 and
cyclic phosphinate 10. The existence of the equilibrium with the start-
ing materials on the thermal conditions was found by the thermolyses
SCHEME 2

Heterocycles Derived from Iminophosphorane
1687
SCHEME 3
of 5 in the presence of water, methanol, and 4, which gave 10,
methoxyphosphorane 11, and 7, respectively (Scheme 2).
The thermolysis of 1,3,2 5-diazaphosphetidine-4-thione 6, afforded
not only the starting materials, 1 and 3, but also cyclic thiophos-
phinate 12 and diphenylcarbodiimide 13. The formation of 12 and
5
13 strongly suggests the generation of the corresponding 1,3,2
thiazaphosphetidine 14 as an intermediate (Scheme 3).
-
1,2 5-Azaphosphetine 7 is thermally quite stable, in contrast to 5
and 6. It did not decompose even upon heating at 180 C. It is inactive
toward the Wittig reactions with benzaldehyde and phenyl isocyanate.
In summary, we have revealed that 1,3,2 5-oxazaphosphetidine 5
and 1,3,2 5-diazaphosphetidine-4-thione 6, which were obtained from
an iminophosphorane 1, have two reactivities including the regenera-
tion of 1. Meanwhile, 1,2 5-azaphosphetine 7 is quite thermally stable.
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