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Isolation of pentacoordinate species during reactions of five-membered cyclic phosphates an —evidence for pentacoordinate intermediates—
TetrahedronLetters No. 12, pp 1075 - 1078, 1974.
PergamonPress. Printed in Great Britain.
ISOLATIONOF PENTACOORDINATESPECIES DURING REACTIONSOF FIVE-MEMBEREDCYCLIC PHOSPHATES
-
AN EVIDENCEFOR PENTACOORDINATE IWTERMEDIATES-
T0i-u koizumi: Faculty
Yutaka Watanabe,
of Pharmaceutical
(Received
Sciences,
Yuichi
Yoshida,
University
and Eiichi
Yoshii
of Toyama, Cofuku,
Toyama, Japan
in Japan 5 Februaq 1974; receivedin UK for publication12 Fleba'uaa'y 1974)
Since Westheimerfirst proposed the pseudorotationmechanismof pentacoordinateintermediates
1) , there have been reportedmany evidences for the hydrolysisof five-memberedcyclic phosphates supportingthe mechanism. Among those, followingfacts are consideredto be most important: 2, 3) , 2) Rate enhancementin the reaction of 1) TemperaturedependentNMR of phosphoranes 5, 6) 4)3) Rate limitingpseudorotation and related phenomenon. strainedcyclic phosphinates, However 1) concernsonly with the pseudorotational formed,
2) and 3) suggest
None of them directly the displacement
verifies
reaction
’ Is pentacoordinate We report
here
found that
of
the discrete
clear
reaction
the course
of
of
really
at least
our studies
phosphorylation
with phenyl of alcohols”).
the same procedure When catechol of
was crystalline this
the formation
some five-membered on the phosphorus
In continuation
and obtained was heated
triethylamine solid solid
(IV)
8,
(II) unexpected
with
reaction
one equivalent
82%) which
is
are shown in Table
containing
study,
intermediate
heterocyclic prepared that
compounds,
I.
product
by the reaction I was useful
we undertook
of
for
the
the synthesis
phosphorodichloridate
II was not obtained in common organic
To our surprise,
1075
we
(III)
of by
products. of phenyl
insoluble
during
phosphates.
9) and suggested of this
question
.
and 2-phenoxy-benzoxazaphosphole-2-oxide
in THF, the expected
(yield
of pentacoordinate cyclic
during
the important
to be solved 7)
remains
if
indirectly.
intermediates
Therefore,
was easily
(I)
intermediates
rather
of pentacoordinate
’ still
phosphorodichloridate
2-phenoxy-benzodioxaphosphole-2-oxide
data of
for
formation
phosphates.
2-phenoxy-benzodiazaphosphole-2-oxide
o-phenylenediamine
presence
cyclic formed?
support
of pentacoordinate
intermediates formation
five-membered
intermediate
the first
the displacement During
the pentacoordinate
process
these
and instead
solvents. data
under the
fit
isolated
The physical quite
well
with
1076
No. 12
those
of triethylammonium
tris(o-phenylenedioxy)phosphate
by the reaction
of hexachlorocyclotriphosphazene
in the presence
of triethylamine
established
by X ray analysis
Thus the structure the direct according
of
Next -o-aminophenol as above and in this a small
quite
IR with
to the Allcock’s
has been
Et$H
IV has been confirmed
was treated
case
0’ ‘0
by
Iv
V and VI.
Molecular
I.
phosphorodichloridate
product
Physical
Formula
III
Properties
was obtained
along
data of V and VI are shown in Table of
IV, V, and VI.
Mass Spectra
UV
IR KBr cm-1 ) &ma,
(m/e)
3180,
356 (M+), 264
C24H28N06P
under the same condition
(bp 210”C/10-3mmHg)13)
The physical
(“C) >238
0
dp%
of the compound prepared
with phenyl
the expected
Table
IV
247,
172,156
1490,
139,
110
825,
(mu (loge)) 227(3.78)a)
1600
280(3.75)
1245 750,
284 (3.78)
730
290(3.68) V
C18H16N303P
225(dec.)
352(M+-1)
3390,
3220,
1610
236(4.10)b)
244,
1580,
1320,
1300
286(3.92)
137
C18H15N203P
206-207
337(M+-1)
3440,
3220,
1615
244,
1590,
1330,
1230
137
Again
the physical
properties
phenoxy phosphorane14)
cyclotriphosphazene.
specimen
The structure -phenoxy with
those
of VI was determined
phosphorane of V.
by comparison
with
synthesized
286(4.11)
in dioxane
those
of bis-(o-phenyleneoxyamino)-2-amino-
by Allcock
-
with hexachloro-
the structure
mp and IR with
by the Allcock’s
b)
well
of o-aminophenol
Accordingly,
by comparing prepared
of V fit
which was
and Kugel by the reaction
confirmed
in acetonitrile
236(4. 19)b) 291(4.06)
690
93
a)
291(3.88)
1225
107 VI
11)
catechol
12) .
recently
that
by Allcock
procedure.
amount of by-products,
mp
with
and whose structure
of the product
comparison
which has been synthesized
those
of
of V was standard
00
o-
1 ,OAr ;--+
OO ti
procedure. as bis-(g-phenyleneoxyamino)of the physical
properties
NH
V : Ar = o-NH.# VI:
At=+
I.
with
No.
1077
12
Although it
complex,
the formation is
a possibility
oxazaphosphole-2-oxide V, and VI. coordinate
If
with
these
once
to clarify
the compound IV was obtained oxide(mp III
152-154”C)‘5)
was treated
results of
easy
formation
nature
considered following
with
indicate
catechol
of
the stable
further
should
this
possibility,
of triethylamine
reactions
also
direct
the reaction was carried
furnished
of
under the mild
pentacoordinate
II
compounds should
the mechanism of the formation
to be complex
and awaits
further
mechanism may be a reasonable
cyclic
(bp 160°C/0.07mmHg)15) THF.
As expected,
On the other
hand,
have been isolated. intermediates conditions.
during
the reactions
The reason
be attributed
when These
for
to the very
of
IV, V, and VI by the reaction
detailed
investigations
of
this stable
including
II and III
kinetics,
one.
0
.
II(X,Y=O) Y=NH)
the penta-
phosphoranes. 2)
a IIl(X=O,
Iy,
2-anilino-benzodioxaphosphole-2-
IV in 28% yield.
the pentacoordinate
and -o-aminophenol
five-membered
of
to give
to support
out in refluxing
in THF, V(5%) and VI(trace) of
or o-aminophenol evidence
of
may be rather
II or 2-phenoxy-benz-
catechol
reaction
16). The reaction
in 37% yield catechol
with
be the first
by the displacement
the formation
with
of bicyclic
Although
it
with o-aminophenol
clearly
II and III
formed reacts
formation
in the presence
IV, V, and YI in the above
2-phenoxy-benzodioxaphosphole-2-oxide
are the cases,
In order
catechol
that
III
intermediate
phosphates.
mechanism of
HY
d
0 - Hz0
VI(X=O,Y=NH)
J
-Hz0
rv( X,Y q 0 1 V(X=O.Y=N”)
is
No. 12
1078
The conversionof VI to V during the reaction is unlikelybecause the reaction of VI with o-aminophenoldid not give V under the similar reaction condition, The role of II and III as the dehydratingagents ( as well as the substrates)may be the key for this interesting reactions. Referencesand Notes 1)
F. H. Westheimer,Accounts of Chem. Research,!, 70(1968).
2)
F. Ramirez, Accounts of Chem. Research,A, 168(1968).
3) D. G. Gorenstein,and F. H. Westheimer,J. Amer. Chem. Sot., 82, 2762(1967). 4) W. Hawes, and S. Trippett,Chem. Comm., 1968, 577. P. Haake, R. D. Cook, T. Koizumi,P. S. Ossip, W. Schwarz,and D. A. Tyssee, J. Amer. Chem. --&.,
92, 3828(1970).
4143(1969). 5) R. Kluger, and F. H. Westheimer,J. Amer. Chem. Sot., 91, = 6) R. D. Cook, P. C. Turley, C. E. Diebert,A. H. Fierman,and P. Haake, J. Amer. Chem. Sot., 94, 9260(1972). 7) R. F. Hudson, and C. Brown describedthe same point of view in their review appeared in Accounts of Chem. Research,2, 204(1972). 8)
2-phenoxy-l,3-dihydro-2H-1,3,2-benzodiazaphosphole-2-oxide is a formal nomenclaturefor this compound. In this paper the conventionalnames are used for this class of compounds.
9) T. Koizumi,Y. Arai, and E. Yoshii, Chem. Pharm. Bull., 2,
202(1973).
10) T. Koizumi,Y. Arai, and E. Yoshii, TetrahedronLetters,1973, 4763. 11) H. R. Allcock,J. Amer. Chem. Sot., 86, 2591(1964). 12) H. R. Allcock, and E. C. Bissell.J. Amer. Chem. Sot., 2, 3154(1973). 13) Satisfactoryelementalanalysesand spectraldata were obtainedon all new compounds. 91, 5452(1969). Although it 14) H. R. Allcock, R. L. Kugel, J. Amer. Chem. Sot., =
is not
certain which of oxygen and nitrogen occupy apical position,the structurewith apical oxygen is employedfor convenience. were preparedby the reactionof phenylenephos15) II and 2-anilino-benzodioxaphosphole-2-oxide phorochloridatewith phenol or aniline in the presence of triethylamine. These compounds are easily hydrolyzedunder mild conditionand the mechanismof the hydrolysisis now being investigated. 16) The yield is based on II employed.
-
PergamonPress. Printed in Great Britain.
ISOLATIONOF PENTACOORDINATESPECIES DURING REACTIONSOF FIVE-MEMBEREDCYCLIC PHOSPHATES
-
AN EVIDENCEFOR PENTACOORDINATE IWTERMEDIATES-
T0i-u koizumi: Faculty
Yutaka Watanabe,
of Pharmaceutical
(Received
Sciences,
Yuichi
Yoshida,
University
and Eiichi
Yoshii
of Toyama, Cofuku,
Toyama, Japan
in Japan 5 Februaq 1974; receivedin UK for publication12 Fleba'uaa'y 1974)
Since Westheimerfirst proposed the pseudorotationmechanismof pentacoordinateintermediates
1) , there have been reportedmany evidences for the hydrolysisof five-memberedcyclic phosphates supportingthe mechanism. Among those, followingfacts are consideredto be most important: 2, 3) , 2) Rate enhancementin the reaction of 1) TemperaturedependentNMR of phosphoranes 5, 6) 4)3) Rate limitingpseudorotation and related phenomenon. strainedcyclic phosphinates, However 1) concernsonly with the pseudorotational formed,
2) and 3) suggest
None of them directly the displacement
verifies
reaction
’ Is pentacoordinate We report
here
found that
of
the discrete
clear
reaction
the course
of
of
really
at least
our studies
phosphorylation
with phenyl of alcohols”).
the same procedure When catechol of
was crystalline this
the formation
some five-membered on the phosphorus
In continuation
and obtained was heated
triethylamine solid solid
(IV)
8,
(II) unexpected
with
reaction
one equivalent
82%) which
is
are shown in Table
containing
study,
intermediate
heterocyclic prepared that
compounds,
I.
product
by the reaction I was useful
we undertook
of
for
the
the synthesis
phosphorodichloridate
II was not obtained in common organic
To our surprise,
1075
we
(III)
of by
products. of phenyl
insoluble
during
phosphates.
9) and suggested of this
question
.
and 2-phenoxy-benzoxazaphosphole-2-oxide
in THF, the expected
(yield
of pentacoordinate cyclic
during
the important
to be solved 7)
remains
if
indirectly.
intermediates
Therefore,
was easily
(I)
intermediates
rather
of pentacoordinate
’ still
phosphorodichloridate
2-phenoxy-benzodioxaphosphole-2-oxide
data of
for
formation
phosphates.
2-phenoxy-benzodiazaphosphole-2-oxide
o-phenylenediamine
presence
cyclic formed?
support
of pentacoordinate
intermediates formation
five-membered
intermediate
the first
the displacement During
the pentacoordinate
process
these
and instead
solvents. data
under the
fit
isolated
The physical quite
well
with
1076
No. 12
those
of triethylammonium
tris(o-phenylenedioxy)phosphate
by the reaction
of hexachlorocyclotriphosphazene
in the presence
of triethylamine
established
by X ray analysis
Thus the structure the direct according
of
Next -o-aminophenol as above and in this a small
quite
IR with
to the Allcock’s
has been
Et$H
IV has been confirmed
was treated
case
0’ ‘0
by
Iv
V and VI.
Molecular
I.
phosphorodichloridate
product
Physical
Formula
III
Properties
was obtained
along
data of V and VI are shown in Table of
IV, V, and VI.
Mass Spectra
UV
IR KBr cm-1 ) &ma,
(m/e)
3180,
356 (M+), 264
C24H28N06P
under the same condition
(bp 210”C/10-3mmHg)13)
The physical
(“C) >238
0
dp%
of the compound prepared
with phenyl
the expected
Table
IV
247,
172,156
1490,
139,
110
825,
(mu (loge)) 227(3.78)a)
1600
280(3.75)
1245 750,
284 (3.78)
730
290(3.68) V
C18H16N303P
225(dec.)
352(M+-1)
3390,
3220,
1610
236(4.10)b)
244,
1580,
1320,
1300
286(3.92)
137
C18H15N203P
206-207
337(M+-1)
3440,
3220,
1615
244,
1590,
1330,
1230
137
Again
the physical
properties
phenoxy phosphorane14)
cyclotriphosphazene.
specimen
The structure -phenoxy with
those
of VI was determined
phosphorane of V.
by comparison
with
synthesized
286(4.11)
in dioxane
those
of bis-(o-phenyleneoxyamino)-2-amino-
by Allcock
-
with hexachloro-
the structure
mp and IR with
by the Allcock’s
b)
well
of o-aminophenol
Accordingly,
by comparing prepared
of V fit
which was
and Kugel by the reaction
confirmed
in acetonitrile
236(4. 19)b) 291(4.06)
690
93
a)
291(3.88)
1225
107 VI
11)
catechol
12) .
recently
that
by Allcock
procedure.
amount of by-products,
mp
with
and whose structure
of the product
comparison
which has been synthesized
those
of
of V was standard
00
o-
1 ,OAr ;--+
OO ti
procedure. as bis-(g-phenyleneoxyamino)of the physical
properties
NH
V : Ar = o-NH.# VI:
At=+
I.
with
No.
1077
12
Although it
complex,
the formation is
a possibility
oxazaphosphole-2-oxide V, and VI. coordinate
If
with
these
once
to clarify
the compound IV was obtained oxide(mp III
152-154”C)‘5)
was treated
results of
easy
formation
nature
considered following
with
indicate
catechol
of
the stable
further
should
this
possibility,
of triethylamine
reactions
also
direct
the reaction was carried
furnished
of
under the mild
pentacoordinate
II
compounds should
the mechanism of the formation
to be complex
and awaits
further
mechanism may be a reasonable
cyclic
(bp 160°C/0.07mmHg)15) THF.
As expected,
On the other
hand,
have been isolated. intermediates conditions.
during
the reactions
The reason
be attributed
when These
for
to the very
of
IV, V, and VI by the reaction
detailed
investigations
of
this stable
including
II and III
kinetics,
one.
0
.
II(X,Y=O) Y=NH)
the penta-
phosphoranes. 2)
a IIl(X=O,
Iy,
2-anilino-benzodioxaphosphole-2-
IV in 28% yield.
the pentacoordinate
and -o-aminophenol
five-membered
of
to give
to support
out in refluxing
in THF, V(5%) and VI(trace) of
or o-aminophenol evidence
of
may be rather
II or 2-phenoxy-benz-
catechol
reaction
16). The reaction
in 37% yield catechol
with
be the first
by the displacement
the formation
with
of bicyclic
Although
it
with o-aminophenol
clearly
II and III
formed reacts
formation
in the presence
IV, V, and YI in the above
2-phenoxy-benzodioxaphosphole-2-oxide
are the cases,
In order
catechol
that
III
intermediate
phosphates.
mechanism of
HY
d
0 - Hz0
VI(X=O,Y=NH)
J
-Hz0
rv( X,Y q 0 1 V(X=O.Y=N”)
is
No. 12
1078
The conversionof VI to V during the reaction is unlikelybecause the reaction of VI with o-aminophenoldid not give V under the similar reaction condition, The role of II and III as the dehydratingagents ( as well as the substrates)may be the key for this interesting reactions. Referencesand Notes 1)
F. H. Westheimer,Accounts of Chem. Research,!, 70(1968).
2)
F. Ramirez, Accounts of Chem. Research,A, 168(1968).
3) D. G. Gorenstein,and F. H. Westheimer,J. Amer. Chem. Sot., 82, 2762(1967). 4) W. Hawes, and S. Trippett,Chem. Comm., 1968, 577. P. Haake, R. D. Cook, T. Koizumi,P. S. Ossip, W. Schwarz,and D. A. Tyssee, J. Amer. Chem. --&.,
92, 3828(1970).
4143(1969). 5) R. Kluger, and F. H. Westheimer,J. Amer. Chem. Sot., 91, = 6) R. D. Cook, P. C. Turley, C. E. Diebert,A. H. Fierman,and P. Haake, J. Amer. Chem. Sot., 94, 9260(1972). 7) R. F. Hudson, and C. Brown describedthe same point of view in their review appeared in Accounts of Chem. Research,2, 204(1972). 8)
2-phenoxy-l,3-dihydro-2H-1,3,2-benzodiazaphosphole-2-oxide is a formal nomenclaturefor this compound. In this paper the conventionalnames are used for this class of compounds.
9) T. Koizumi,Y. Arai, and E. Yoshii, Chem. Pharm. Bull., 2,
202(1973).
10) T. Koizumi,Y. Arai, and E. Yoshii, TetrahedronLetters,1973, 4763. 11) H. R. Allcock,J. Amer. Chem. Sot., 86, 2591(1964). 12) H. R. Allcock, and E. C. Bissell.J. Amer. Chem. Sot., 2, 3154(1973). 13) Satisfactoryelementalanalysesand spectraldata were obtainedon all new compounds. 91, 5452(1969). Although it 14) H. R. Allcock, R. L. Kugel, J. Amer. Chem. Sot., =
is not
certain which of oxygen and nitrogen occupy apical position,the structurewith apical oxygen is employedfor convenience. were preparedby the reactionof phenylenephos15) II and 2-anilino-benzodioxaphosphole-2-oxide phorochloridatewith phenol or aniline in the presence of triethylamine. These compounds are easily hydrolyzedunder mild conditionand the mechanismof the hydrolysisis now being investigated. 16) The yield is based on II employed.
-