Reactions of N-alkyl- and N-aryltrihalogenoacetamides with phosphorus pentachloride

Article abstract of DOI:10.1007/s11172-005-0316-2

In the study of reactions of N-alkyl- and N-aryltrihalogenoacetamides with PCl₅, it was demonstrated for the first time that 3-alkyl(aryl)-2,2,2,4 tetrachloro-4-trihalomethyl-1,3,2-λ⁵- oxazaphosphetanes are intermediates in the synth

Full text of DOI:10.1007/s11172-005-0316-2

752
Russian Chemical Bulletin, International Edition, Vol. 54, No. 3, pp. 752—757, March, 2005
Reactions of Nꢀalkylꢀ and Nꢀaryltrihalogenoacetamides
with phosphorus pentachloride
ꢀ
A. D. Sinitsa, A. A. Shalimov, A. M. Nesterenko, and D. M. Malenko
Institute of Organic Chemistry, National Academy of Sciences of the Ukraine,
5
ul. Murmanskaya, 02660 Kievꢀ94, Ukraine.
Eꢀmail: ioch@bpci.kiev.ua
In the study of reactions of Nꢀalkylꢀ and Nꢀaryltrihalogenoacetamides with PCl , it was
5
demonstrated for the first time that 3ꢀalkyl(aryl)ꢀ2,2,2,4ꢀtetrachloroꢀ4ꢀtrihalomethylꢀ1,3,2ꢀ
5
λ ꢀoxazaphosphetanes are intermediates in the synthesis of trihaloacetimidoyl chlorides. Acꢀ
cording to quantumꢀchemical calculations, acyclic Nꢀtetrachlorophosphoranes, which are the
primary products in the reactions of trihaloacetamides with PCl , undergo rapid cyclization
5
into the corresponding phosphorates and subsequent 1,3ꢀchlorotropic migration gives rise to
oxazaphosphetanes with the fiveꢀcoordinate P atom.
Key words: trihaloacetamides, phosphorus pentachloride, tetrachlorophosphoranes, imidoyl
chlorides, oxazaphosphetanes, quantum chemical calculations.
Reactions of Nꢀmonosubstituted carboxamides with
PCl and other chlorophosphoranes are most common
Scheme 2
5
1
,2
and preparative routes to imidoyl chlorides. Although
the available experimental material concerning the synꢀ
thesis of imidoyl chlorides is abundant, only a few studies
have reported the attempts to isolate intermediate prodꢀ
ucts in these reactions and investigate the reaction mechaꢀ
nisms. This mainly refers to halogeno carboxylic acid deꢀ
rivatives, for which the reaction pathways and the yields
of final products have been found to depend on the nature
of the halogen atom and the substituent at the N atom.
3
According to the generally accepted assumption, reꢀ
actions of Nꢀsubstituted carboxamides with PCl proceed
5
via intermediate acyclic Oꢀtetrachlorophosphoranes
Presumably,7 the reaction of PCl5 with perꢀ
(
Scheme 1).
fluoroglutarimide affords Oꢀtetrachlorophosphorane
(
Scheme 3); however, reliable data confirming its formaꢀ
Scheme 1
tion and structure are missing.
Scheme 3
The reactions of imides (Scheme 2) with PCl yield
The formation of a mixture of Oꢀ and Nꢀtetrachloroꢀ
phosphoranes was postulated for the reaction of
5
4
—6
8
isomeric imidoyl chlorides.
The corresponding chloroꢀ
phosphoranes as possible intermediates of these reactions
have not been identified.
Nꢀmethyltrifluoroacetamide (1a) with PCl (Scheme 4).
It was concluded that imidoyl chloride 2a and POCl3
5
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 739—744, March, 2005.
066ꢀ5285/05/5403ꢀ0752 © 2005 Springer Science+Business Media, Inc.
1

Reactions of trihalogenoacetamides with PCl5
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
753
Scheme 4
(
pathway a) are formed from Oꢀtetrachlorophosphorane,
gen chloride catalyzes their decomposition, which was
confirmed in an independent experiment. The use of
while the dimer of methylimidophosphine trichloride 3a
and trifluoroacetyl chloride (pathway b) are the decomꢀ
position products of Nꢀtetrachlorophosphorane.
However, in this case too, neither type of chloroꢀ
phosphoranes was isolated or characterized.
Nꢀtrimethylsilylamides in the reactions with PCl preꢀ
5
cludes the formation of HCl and affords the target prodꢀ
ucts in high yields.
In the presence of HCl, phosphetanes 4 decompose
just in the course of the reaction in two competitive
pathways a and b (see Scheme 5). For Nꢀmethyltetraꢀ
chloro(trifluoromethyl)oxazaphosphetane 4a, the ratio of
the imidoyl chloride 2a and trifluoroacetyl chloride
was virtually identical with that reported earlier.8
Oxazaphosphetanes decomposed rapidly when heated to
80—120 °C. The decomposition temperature and the raꢀ
tio of the products are determined by the nature of the
substituents at the N atom. For R = Me and Bu, both
decomposition pathways are approximately equally probꢀ
In continuation of investigations9 into phosphoryꢀ
,10
lation of halogeno carboxamides, we studied reactions of
PCl with Nꢀalkylꢀ and Nꢀarylpolyhalogenocarboxamides.
NꢀAlkyltrihalogenoacetamides and trihalogenoacetaniliꢀ
des 1a—f reacted with PCl under mild conditions. The
phosphorylation rate depended on the nature of the subꢀ
stituents at the N atom (e.g., with the tertꢀbutyl substituꢀ
ent, no reaction occurred). Oxazaphosphetanes 4a—f were
the reaction products (Scheme 5).
5
5
able; the formation of imidoyl chloride and POCl is
3
Scheme 5
dominant with a branched (Nꢀisopropyl) radical. The presꢀ
ence of Nꢀphenyl group substantially reduces the stability
of the intermediate and favors the dominance (up to 75%)
of dimeric trichloro(Nꢀphenylimino)phosphine and triꢀ
haloacetyl chloride. The presence of the trihalomethyl or
other electronꢀwithdrawing groups at the C atom is preꢀ
requisite for the stabilization of the oxazaphosphetane
ring. Oxazaphosphetanes with weaker electron acceptors
at the C atom are less stable. This is evident from the fact
that the reactions of Nꢀsubstituted amides of aromatic
(
benzoic, pꢀnitrobenzoic, and perfluorobenzoic) and aliꢀ
phatic (pivalic and isobutyric) carboxylic acids with PCl5
yielded no oxazaphosphetanes.
The formation of oxazaphosphetane 4g in the reaction
of Nꢀmethyldichloroacetamide (1g) with PCl was conꢀ
5
firmed by spectroscopic methods. However, the final reꢀ
action product was trichloroacetimidoyl chloride (2e)
rather than a dichloro analog as the result of chlorination
of the dichloromethyl group (Scheme 6).
The formation of oxazaphosphetanes can proceed via
intermediate acyclic Nꢀ or Oꢀtetrachlorophosphoranes,
which undergo cyclization into tetrachlorophosphorates
upon the attack of the carbonyl O atom or the N atom on
the electrophilic P atom. Subsequent 1,3ꢀchlorotropic
migration in the phosphorates leads to the corresponding
tetrachlorooxazaphosphetanes with the fiveꢀcoordinate
i
X = F, R = Me (a), Bu (b), Pr (c), Ph (d); X = Cl, R = Me (e), Ph (f).
The structures of oxazaphosphetanes 4 were confirmed
by spectroscopic data; in addition, some of them (4a,c,e)
were identical with compounds synthesized earlier from
Nꢀchlorotrihaloacetamides and PCl3.
Most of the oxazaphosphetanes obtained are liquids
that can be distilled in vacuo and are easily hydrolyzed by
atmospheric moisture. Like dimeric trichloro(imino)phosꢀ
phines, oxazaphosphetanes are resistant to SO2. The
distilled liquids are stable for a long period of time. Hydroꢀ
1
0
1
1

754
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
Sinitsa et al.
Scheme 6
intermediates (9) are more polar (by 2 to 3 D) than acyꢀ
clic ones (7, 8), which also favors the cyclization along
pathways a and b in polar media (see Scheme 7). Thus,
acyclic Nꢀ or Oꢀtetrachlorophosphoranes (7, 8) can imꢀ
mediately be converted into phosphorates (9). The cyꢀ
clization along pathway a occurs somewhat more easily
because of its lower energy of activation (see Table 1).
Subsequent 1,3ꢀchlorotropic migration in phosꢀ
phorates (9) gives tetrachlorooxazaphosphetanes (4) with
the fiveꢀcoordinate P atom; their energies are substanꢀ
tially lower than those of the corresponding bipolar isoꢀ
mers (9) (δ∆E = 84.4 (R = Me) and 83.2 kJ mol–
(R = Ph)). The fairly high energies of activation of
1,3ꢀchlorotropic migration are lowered owing to coordiꢀ
nation of the transition states with hydrogen chloride
or to the solvation effects. Our data are in qualitative
agreement with those obtained for tetrachlorodiazaꢀ
P atom. Most likely, primary reaction products are
Nꢀphosphorylated derivatives. An alternative pathway imꢀ
plying a direct attack of the carbonyl O atom on the
P atom seems to be less probable because in this case, the
acyl substituents at the N atom, which enhance the elecꢀ
trophilicity of phosphorus, would favor cyclization and
stabilization of oxazaphosphetanes.
To determine the most probable pathway for
the formation of the phosphoranes, we performed
ab initio RHF/6ꢀ31+G(d,p) and B3LYP/6ꢀ31+G(d,p)
GAMESS12 calculations of possible intermediates in
1
1
3
phosphetanes.
According to our calculations, the nature of substituꢀ
ent R (R = Me or Ph) at the amide N atom affects the
course of the reactions insignificantly. It is worth noting
that the thermodynamic characteristics of these processes
in vacuo differ little from those obtained with considerꢀ
the reactions of trihalogenoacetamides with PCl with
Nꢀmethylꢀ and Nꢀphenyltrifluoroacetamides as examples
5
1
4
(
Scheme 7).
ation of the solvent effect in terms of the PCM model
(∆Esolv = –25.2 (7a) and –16.3 kJ mol (8a)).
–
1
The results of the calculations are given in Table 1.
According to the RHF/6ꢀ31+G(d,p) data, Nꢀpreꢀreacꢀ
tion complexes 5 are thermodynamically more favorable
Introduction of halogen atoms into the aromatic ring
of Nꢀaryltrihalogenoacetamides significantly affects the
–
1
(
δ∆E = 56.8 (R = Me) and 72.7 kJ mol (R = Ph)) than
direction of their reactions with PCl . For instance,
5
their Oꢀanalogs (6). Although the initially formed putaꢀ
tive Nꢀtetrachlorophosphoranes (7) and Oꢀisomers (8)
are similar in thermodynamic stabilities, the formation of
the former is more favorable (δ∆E = 13.3 (R = Me) and
Nꢀpentafluorophenyltrifluoroꢀ and ꢀtrichloroacetamides
react with PCl to give only trichloro(Nꢀpentafluoroꢀ
5
1
5
phenylimino)phosphine, while Nꢀpentachlorophenyltriꢀ
chloroacetamide affords the corresponding imidoyl chloꢀ
1
0.6 kJ mol–1 (R = Ph)). According to the scheme, the
ride in moderate yield.
16
next reaction step is cyclization of Nꢀ or Oꢀtetrachloroꢀ
phosphoranes into phosphorates (9), which are more stable
Thus, our calculations showed that in the reactions of
Nꢀsubstituted trihalogenoacetamides with PCl , Nꢀtetraꢀ
5
–
1
than acyclic isomers (7, 8) (δ∆E = 4.6 and 17.9 kJ mol
chlorophosphoranes (7) are the most probable intermediꢀ
ates; they are rapidly converted into cyclic tetrachloroꢀ
–
1
for R = Me and 2.9 and 13.8 kJ mol for R = Ph). Cyclic
Scheme 7
i. 1,3ꢀmigration.

Reactions of trihalogenoacetamides with PCl5
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
755
Table 1. Thermodynamic characteristics of the intermediates in the reactions of Nꢀmethylꢀ and Nꢀphenyltrifluoroacetamides with
PCl according to the RHF/6ꢀ31+G(d,p) and B3LYP/6ꢀ31+G(d,p) calculations
5
Process
Initial state
ZPE
Transition state
ZPE
E#
Final state
–
E
µ
–E
–ν1
µ
–E
ZPE
δ∆E
µ
/
D
/cm–1 /D
/D
au
au
au
RHF/6ꢀ31+G(d,p)
5
7
9
6
8
5
7
9
6
8
a → 7a
a → 9a
a → 4a
a → 8a
a → 9a
b → 7b
b → 9b
b → 4b
b → 8b
b → 9b
3181.61587
2721.54835
2721.55012
3181.58819
2721.54329
3372.22274
2912.01348
2912.01464
3372.04860
2912.00945
0.09579 4.6
0.07651 3.7
0.07718 5.6
0.09502 2.4
0.07592 2.2
0.15243 4.0
—
—
0.07632
0.07665 80.3 132.6 7.5
—
0.07632
—
0.12759
0.12762 81.9 120.2 8.6
—
—
—
2721.54835
2721.55012
2721.58228
2721.54329
2721.55012
2912.01348
2912.01464
2912.04644
2912.00945
2912.01464
0.07651
0.07718
0.07775 –84.4 2.4
0.07592 2.2
0.07718 –17.9 5.6
0.12756
0.12841
0.12888 –83.2 3.5
0.12734 2.3
—
3.7
2721.54074
2721.51958
—
2721.54074
—
5.0 116.4 4.4
–4.6 5.6
—
—
—
—
6.7 116.4 3.3
—
4.6 119.6 5.5
—
—
—
5.1
0.12756 5.1 2912. 01174
–2.9 6.4
0.12841 6.4
0.15231 1.7
0.12734 2.3
2911.98340
—
2912.00715
—
0.12775
—
5.6
—
—
—
73.8 3.6
0.12841 –13.8 6.4
В3LYP/6ꢀ31+G(d,p)
0.07637 4.6 34.8 2.8
0.07384 61.9 270.0 4.2
0.07616 88.6 250.7 4.6
7
8
9
a → 9a
a → 9a
a → 4a
2727.69402
2727.69847
2727.71137
0.07620 1.9
0.07564 2.1
0.07683 5.0
2727.69234
2727.67482
2727.67766
2727.71137
2727.71137
2727.72548
0.07683 –45.6 5.0
0.07683 –33.9 5.0
0.07739 –37.2 2.4
Note. E and δ∆E are expressed in kJ mol–1.
#
3ꢀButylꢀ2,2,2,4ꢀtetrachloroꢀ4ꢀtrifluoromethylꢀ1,3,2ꢀλ5ꢀ
oxazaphosphetane (4b). NꢀButyltrifluoroacetamide (1b)
phosphorates (9) and, upon triad migration of the Cl atom,
into oxazaphosphetanes (4).
(
0.186 mol) was added to a suspension of PCl (0.186 mol) in
5
CH Cl (100 mL). The reaction mixture was kept at room temꢀ
2
2
Experimental
perature for 72 h (complete dissolution of PCl ) and concenꢀ
5
trated in vacuo; the residue was distilled. The yield of compound
4b was 68%, b.p. 60—63 °C (0.07 Torr). Found (%): Cl, 41.65;
N, 4.22; P, 9.17. C H Cl F NOP. Calculated (%): Cl, 41.59;
IR spectra were recorded on a URꢀ20 spectrophotometer.
1H, 19F, P, and C NMR spectra were recorded on a Varian
31
13
6
9
4 3
3
1
3
VXRꢀ300 spectrometer (299.15, 282.20, 121.42, and 75.43 MHz,
N, 4.11; P, 9.09. P NMR (CH Cl ), δ: –46.4 (q, JPH
36.8 Hz). F NMR (CH Cl ), δ: –81.9 (s). H NMR (CDCl ),
2 2 3
=
2
2
1
13
19
1
respectively). Chemical shifts are referenced to HMDS ( H, C)
19
and CFCl ( F) as the internal standards and to 85% H PO
δ: 0.94 (t, 3 H, Me); 1.35 (sextet, 2 H, MeCH ); 1.77 (m, 2 H,
2
3
3
4
31
3
3
(
P) as the external standard. The starting amides were preꢀ
MeCH CH ); 3.87 (dt, 2 H, NCH , JHP = 36.4 Hz, J =
2 2 2
1
7
–1
pared according to known procedures.
,2,2,4ꢀTetrachloroꢀ3ꢀmethylꢀ4ꢀtrifluoromethylꢀ1,3,2ꢀλ5ꢀ
8.1 Hz). IR (CCl ), ν/cm : 1080; 1210; 1400; 1475; 2980.
4
5
2
2,2,2,4ꢀTetrachloroꢀ3ꢀisopropylꢀ4ꢀtrifluoromethylꢀ1,3,2ꢀλ ꢀ
oxazaphosphetane (4c). A solution of Nꢀisopropyltrifluoroꢀ
acetamide (1c) (0.0436 mol) in CH Cl (50 mL) was added to a
oxazaphosphetane (4a). A. A solution of Nꢀmethyltrifluoroꢀ
acetamide (1a) (0.1 mol) in CH Cl (50 mL) was added to a
2
2
2
2
suspension of PCl (0.1 mol) in CH Cl (100 mL). The reaction
suspension of PCl5 (0.0436 mol) in CH Cl2 (100 mL). The
5
2
2
2
mixture was left at room temperature for 48 h (complete dissoꢀ
reaction mixture was heated at 40—45 °C for 8 h, and concenꢀ
trated in vacuo; the residue was distilled. The yield of compound
lution of PCl ) and concentrated in vacuo; the residue was disꢀ
5
31
tilled. The yield of compound 4a was 53%, b.p. 60—65 °C
4c was 32%, b.p. 45—50 °C (0.07 Torr). P NMR (CH Cl ), δ:
2 2
(
10 Torr). 3 P NMR (CH Cl ), δ: –46.2 (q, J = 26.0 Hz).
1
3
–48.0 (d, J = 56.6 Hz). F NMR (CH Cl ), δ: –81.1 (s),
PH 2 2
3
19
2
2
PH
19
9
F NMR (CH Cl ), δ: –81.9 (s), which agrees with the literaꢀ
which agrees with the literature data.
2
2
ture data.9
2,2,2,4ꢀTetrachloroꢀ3ꢀphenylꢀ4ꢀtrifluoromethylꢀ1,3,2ꢀλ5ꢀ
oxazaphosphetane (4d). A. A solution of trifluoroacetanilide (1d)
B. Chlorotrimethylsilane (0.015 mol) was added at 10 °C to
a stirred solution of Nꢀmethyltrifluoroacetamide (1a) (0.015 mol)
and triethylamine (0.017 mol) in ether (50 mL). The reaction
mixture was kept at room temperature for 96 h. The precipitate
that formed was filtered off and washed with ether (10 mL). The
solvent was removed under atmospheric pressure. The residue
was dissolved in CH Cl (15 mL) and the solution was added to
(0.05 mol) in CH Cl2 (50 mL) was added to a suspension of
2
PCl (0.05 mol) in CH Cl (150 mL). The reaction mixture was
5
2
2
left at room temperature for 96 h (complete dissolution of PCl5)
and concentrated in vacuo. Trichloro(Nꢀphenylimino)phosphine
dimer was precipitated with light petroleum (40—60 °C, 50 mL)
and filtered off. The solvent was removed in vacuo. The yield of
2
2
15
a stirred suspension of PCl (0.0136 mol) in CH Cl (20 mL).
compound 4d was 38%, nD 1.3985. Found (%): Cl, 39.34;
5
2
2
The mixture was kept at room temperature for 24 h (complete
N, 3.92; P, 8.61. C H Cl F NOP. Calculated (%): Cl, 39.29;
8
5
4 3
N, 3.88; P, 8.58. 3 P NMR (CH Cl ), δ: –45.2. F NMR
1
19
dissolution of PCl ) and concentrated in vacuo. The yield of
5
2 2
13
compound 4a was 94%.
(CH Cl ), δ: –80.6 (s). C NMR (CDCl ), δ: 98.50 (dq, CF C,
2 2 3 3

756
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
Sinitsa et al.
2JCP = 7.6 Hz, J = 40.7 Hz); 132.98 (d, Cipso, 2J = 9.6 Hz);
2
NꢀMethyltrichloroacetimidoyl chloride (2e). A solution of
Nꢀmethyldichloroacetamide (1g) (0.2 mol) in CH Cl (50 mL)
CF
CP
3
1
4
31.02 (d, C , J = 6.7 Hz); 129.61 (s, C ); 129.58 (d, C ,
o CP p m
2
2
3
JCP = 4.3 Hz); 119.40 (qd, CF , J
8.2 Hz). 1H NMR (CDCl ), δ: 7.24 (t, 1 H, H ); 7.39 (t,
H, H ); 7.64 (d, 2 H, H ). IR (CCl ), ν/cm : 1110; 1430;
= 285.7 Hz, JCP
=
was added to a suspension of PCl (0.2 mol) in CH Cl (250 mL).
3
CF
5 2 2
1
2
1
The reaction mixture was left at room temperature until
the dissolution of PCl5 was completed. The formation of
3
p
–
1
m
o
4
5
600; 1650.
2,2,2,4ꢀtetrachloroꢀ4ꢀdichloromethylꢀ3ꢀmethylꢀ1,3,2ꢀλ ꢀoxazaꢀ
B. Chlorotrimethylsilane (0.032 mol) was added to a stirred
phosphetane (4g) was evidenced by an intense signal at δ –48.5
3
31
solution of trifluoroacetanilide (1d) (0.032 mol) and triethylꢀ
amine (0.036 mol) in benzene (200 mL). The reaction mixture
was refluxed for 8 h. The precipitate that formed was filtered off
and washed with benzene (30 mL). The solvent was removed
in vacuo. The residue was dissolved in CH Cl (20 mL) and the
( J
= 27.5 Hz) in the P NMR spectrum of the reaction
PH
mixture. After five days, the solvent was removed in vacuo
and the residue was fractionated. The yield of compound 2e
was 37%, b.p. 54—56 °C (10 Torr), which agrees with the literaꢀ
1
8
ture data.
Thermolysis of oxazaphosphetane 4a.
2
2
solution was added to a stirred suspension of PCl (0.0314 mol)
A solution of
5
in CH Cl2 (30 mL). The reaction mixture was kept at room
compound 4a (0.02 mol) in xylene (8 mL) was refluxed
for 18 h. The mixture was distilled under atmospheric presꢀ
sure. The yield of imidoyl chloride 2a was 1 g (35%), b.p.
49—50 °C (cf. Ref. 8). The residue was kept in vacuo and treated
with light petroleum (5 mL). The precipitate that formed was
filtered off to give 2,2,2,4,4,4ꢀhexachloroꢀ1,3ꢀdimethylꢀ1,3,2,4ꢀ
diazadiphosphetane (3a) (1.4 g, 50%), m.p. 175—177 °C
(cf. Ref. 19).
2
temperature for 48 h (complete dissolution of PCl ) and conꢀ
5
centrated in vacuo. Trichloro(Nꢀphenylimino)phosphine dimer
was precipitated with light petroleum (30 mL) and filtered off.
The solvent was removed in vacuo to give compound 4d in
9
3% yield.
,2,2,4ꢀTetrachloroꢀ3ꢀmethylꢀ4ꢀtrichloromethylꢀ1,3,2ꢀλ5ꢀ
oxazaphosphetane (4e). A. NꢀMethyltrichloroacetamide (1e)
0.12 mol) was added to a suspension of PCl5 (0.12 mol) in
CH Cl (250 mL). The reaction mixture was refluxed for 18 h
2
(
Thermolysis of oxazaphosphetane 4b. Compound 4b
(0.036 mol) was heated to 130 to 135 °C and kept at this temꢀ
perature for 3 h. The mixture was fractionated under atmoꢀ
2
2
and concentrated in vacuo. The residue was treated with light
petroleum (60 mL). The precipitate that formed was filtered off
and washed with light petroleum—benzene (2 : 1) (40 mL). The
spheric pressure. According to 3 P and F NMR data, the fracꢀ
tion with b.p. 100—105 °C (9.2 g) consisted of Nꢀbutyltriꢀ
fluoroacetimidoyl chloride (2b) (δF –71.8) and POCl (δ 3.0).
1
19
31
yield of compound 4e was 45%, m.p. 40—41 °C. P NMR
3
P
3
(
CH Cl ), δ: –46.8 (q, J = 27.4 Hz), which agrees with the
The residue was kept in vacuo at 50 °C for 4 h to give 1,3ꢀdiꢀ
butylꢀ2,2,2,4,4,4ꢀhexachloroꢀ1,3,2,4ꢀdiazadiphosphetane (3b)
(3.68 g, 50%), m.p. 74—75 °C (cf. Ref. 19).
2
2
PH
9
literature data.
B. Chlorotrimethylsilane (0.02 mol) was added at 10 °C to a
stirred solution of Nꢀmethyltrichloroacetamide (1e) (0.021 mol)
and triethylamine (0.025 mol) in ether (100 mL). The reaction
mixture was kept at room temperature for 96 h. The precipitate
that formed was filtered off and washed with ether (20 mL). The
solvent was removed in vacuo and the residue was dissolved in
CH Cl (30 mL). The solution was added to a stirred suspension
Thermolysis of oxazaphosphetane 4c. Compound 4c
(0.08 mol) was heated at 125—130 °C for 4 h. The mixture was
fractionated in vacuo. According to 3 P and F NMR data, the
fraction (6.5 g) with b.p. 35—40 °C (20 Torr) consisted of
Nꢀisopropyltrifluoroacetimidoyl chloride (2c) (δF –71.6) and
POCl (δ 3.0).
1
19
2
2
3
P
of PCl (0.02 mol) in CH Cl (30 mL). The mixture was kept at
Thermolysis of oxazaphosphetane 4d. A solution of comꢀ
pound 4d (0.0363 mol) in toluene (15 mL) was refluxed for
20 min. Two thirds of the solvent was distilled off in vacuo and
the precipitate that formed was filtered off and washed with light
petroleum (10 mL). The yield of 2,2,2,4,4,4ꢀhexachloroꢀ1,3ꢀ
diphenylꢀ1,3,2,4ꢀdiazadiphosphetane (3d) was 6.2 g (75%), m.p.
179—180 °C (cf. Ref. 11). Light petroleum was removed in vacuo
from the filtrate and the residue was distilled to give
Nꢀphenyltrifluoroacetimidoyl chloride (2d) (1.9 g, 24%), b.p.
51—53 °C (10 Torr) (cf. Ref. 20).
5
2
2
room temperature for 48 h (complete dissolution of PCl ) and
5
concentrated in vacuo. The yield of compound 4e was 96%.
5
2
,2,2,4ꢀTetrachloroꢀ3ꢀphenylꢀ4ꢀtrichloromethylꢀ1,3,2ꢀλ ꢀ
oxazaphosphetane (4f). Chlorotrimethylsilane (0.0113 mol)
was added to a stirred solution of trichloroacetanilide (1f)
(
0.0113 mol) and triethylamine (0.014 mol) in benzene (50 mL).
The reaction mixture was kept at room temperature for 96 h.
The precipitate that formed was filtered off and washed with
benzene (20 mL). The solvent was removed in vacuo and the
residue was dissolved in CH Cl2 (15 mL). The solution was
Thermolysis of oxazaphosphetane 4e. A solution of comꢀ
pound 4e (0.01 mol) in xylene (5 mL) was refluxed for 18 h
and then distilled in vacuo. The yield of Nꢀmethyltrichloroꢀ
acetimidoyl chloride (2e) was 0.8 g (41%), b.p. 53—55 °C
(10 Torr) (cf. Ref. 18). The residue was treated with light petroꢀ
leum (10 mL) and the precipitate that formed was filtered off
to give 2,2,2,4,4,4ꢀhexachloroꢀ1,3ꢀdimethylꢀ1,3,2,4ꢀdiazadiꢀ
phosphetane (3a) (0.9 g, 50%), m.p. 174—176 °C.
Thermolysis of oxazaphosphetane 4f. A solution of compound
4f (0.032 mol) in toluene (80 mL) was refluxed for 20 min and
concentrated in vacuo. The precipitate that formed was washed
with light petroleum (30 mL). The yield of 2,2,2,4,4,4ꢀhexaꢀ
chloroꢀ1,3ꢀdiphenylꢀ1,3,2,4ꢀdiazadiphosphetane (3d) was 5 g
(75%), m.p. 179—180 °C.
2
added to a stirred suspension of PCl (0.0113 mol) in CH Cl
5
2
2
(
(
30 mL). The mixture was kept at room temperature for 48 h
complete dissolution of PCl ) and two thirds of the solvent
5
was distilled off in vacuo. The precipitate that formed was filꢀ
tered off and the filtrate was concentrated in vacuo. Triꢀ
chloro(Nꢀphenylimino)phosphine dimer was precipitated with
light petroleum—benzene (1 : 1) (30 mL) at 0 to 5 °C and
filtered off. The solvents were removed in vacuo. The yield of
compound 4f was 62% (90% purity), m.p. 67—70 °C (decomp.).
Found (%): Cl, 60.72; N, 3.60; P, 7.84. C H Cl NOP. Calcuꢀ
8
5
7
–
1
lated (%): Cl, 60.49; N, 3.41; P, 7.55. IR (CCl ), ν/cm : 1100;
360; 1600; 1660. 31P NMR (CH Cl ), δ: –45.6. 1H NMR
4
1
2 2
(
CDCl ), δ: 7.22 (t, 1 H, H ); 7.34 (t, 2 H, H ); 7.56 (d, 2 H, H ).
3 p m o

Reactions of trihalogenoacetamides with PCl5
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
757
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