Novel approach to synthesis of 1,2-dihydrobenz[c][1,2]azaphosphol-3-ones [11]

Full text of DOI:10.1023/A:1017636928966

Chemistry of Heterocyclic Compounds, Vol. 37, No. 4, 2001
NOVEL APPROACH TO SYNTHESIS
c
OF 1,2-DIHYDROBENZ[ ]-
[1,2]AZAPHOSPHOL-3-ONES
A. A. Chekotilo, A. A. Yurchenko, and A. A. Tolmachev
Keywords: m-dimethylaminobenzoic acid, phosphorus tribromide, phosphorylation.
1,2-Dihydrobenz[c][1,2]azaphosphol-3-ones, which can be considered as the phosphorus analogs of
phthalimides, have been little studied [1,2].
We have found that 2-aryl-5-dimethylamino-1,2-dihydrobenz[c][1,2]azaphosphol-3-ones 2 and 3 are
formed on reaction of amides of m-dimethylaminobenzoic acid 1 with phosphorus(III) bromides in pyridine in
the presence of triethylamine at room temperature. The reaction of benzazaphosphole 2 with secondary amines
or 2-substituted imidazo[1,2-a]pyridines followed by addition of elemental sulfur leads to benzazophospholes 4
and 5, respectively. Compound 6 is obtained similarly from benzazaphosphole 3.
Br
P
PBr3
H
N
N
O
R
Me2N
R
Me2N
O
1
2
Me
R =
N
1. NHEt2 2. S8
2. S8
N
Me
1.
N
Me
S
P
S
NEt2
N
R
P
N
R
N
O
Me2N
Me2N
S8
O
4
5
Ph
S
Ph
P
P
PhPBr2
N
O
R
N
O
R
Me2N
Me2N
3
6
__________________________________________________________________________________________
Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev 02056; e-mail:
hetfos@ukrpack.net Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 569-570, April, 2001.
Original article submitted December 9, 2000.
526
0009-3122/01/3704-0526$25.00©2001 Plenum Publishing Corporation

Solution of Bromobenzophosphole 2. Phosphorus tribromide (4.2 mmol) was added dropwise to a
solution of amide 1 (4.2 mmol) [3] and triethylamine (12.6 mmol) in pyridine at 0°C (15 ml). The reaction
mixture was held for 3 h at room temperature, and used without purification for further conversions. We observe
a signal at 110.5 ppm in the 31P NMR spectrum of the reaction mixture.
5
c
1-Diethylamino-5-dimethylamino-2-(4-methylphenyl)-1-thiooxo-1,2-dihydro-1 -benzo[ ][1,2]-
λ
azaphosphol-3-one (4). Diethylamine (4.2 mmol) and then 30 min later elemental sulfur (5 mmol) were added
to the solution of bromobenzphosphole 2. After 12 h, benzene (50 ml) was added and the mixture was stirred,
then the precipitate was filtered off and the filtrate was evaporated down. The residue was chromatographed on
31
silica gel with toluene as the eluent. Yield 67%; mp 201-203°C (ethanol). P NMR spectrum (CDCl3): 63.9
1
ppm. H NMR spectrum (CDCl3), , ppm, J, Hz: 0.83 (6H, t, N(CH2CH3)2); 2.38 (3H, s, CH3; 3.02 (2H, m,
δ
3
4
4
NCH2CH3); 3.10 (6H, s, N(CH3)2); 3.22 (2H, m, NCH2CH3); 6.95 (1H, m, JHH = 8.7, JHH = 2.1, JHP = 3.9,
6-H); 7.3 (5H, m, 4-H, NC6H4CH3); 7.6 (1H, dd, 3JHH = 8.7, 3JHP = 11.7, 7-H). Found, %: N 10.73, 10.82; P 7.93,
7.95. C20H26N3OPS. Calculated, %: N 10.84; P 7.99.
a
5-Dimethylamino-1-(2-methylimidazo[1,2- ]pyridin-3-yl)-2-(4-methylphenyl)-1-thiooxo-1,2-dihydro-
5
c
2-Methylimidazo[1,2-a]pyridine (4.2 mmol) and then 30 min later
1 -benz[ ][1,2]azaphosphol-3-one (5).
λ
elemental sulfur (5 mmol) were added to the solution of bromobenzphosphole 2. After 12 h, benzene (50 ml)
was added to the reaction mixture and the mixture was stirred, then the precipitate was filtered off and the
filtrate was evaporated down, and the residue was recrystallized from toluene. Yield 35%; mp 251-253°C
(toluene). 31P NMR spectrum (CDCl3); 37.6 ppm. H NMR spectrum (CDCl3), , ppm, J, Hz: 2.16 (3H, s,
1
δ
3
3
2'-CH3); 2.30 (3H, s, NC6H4CH3); 3.16 (6H, s, N(CH3)2); 6.74 (1H, t, JHH = 7.1, 6'-H); 6.96 (2H, d, JHH = 7.9,
o-CH3C6H4); 7.00 (1H, m, 6-H); 7.10 (2H, d, 3JHH = 7.9, m-CH3C6H4); 7.32 (1H, dd, 3JHH = 7.1, 3JHH = 8.5, 7'-H);
3
3
3
7.38 (3H, br. s, 4-H); 7.61 (1-H, br. d, JHH = 8.5, 8'-H); 7.67 (1H, dd, JHH = 8.7, JHP = 11.7, 7-H); 9.1 (1-H,
br. d, 3JHH = 7.1, 5'-H). Found, %: N 12.46, 12.51; P 6.87, 6.91. C24H25N4OPS. Calculated, %: N 12.55; P 6.94.
5
c
5-Dimethylamino-2-(4-methylphenyl)-1-phenyl-1-thiooxo-1,2-dihydro-1 -benzo[ ][1,2]-azaphosphol-
λ
3-one (6). Dibromophenylphosphine (4.2 mmol) was added dropwise to a solution of amide 1 (4.2 mmol) [3]
and triethylamine (12.6 mmol) in pyridine (15 ml) at 0°C, and then the mixture was allowed to stand for 4.5 h at
room temperature. Then elemental sulfur (5 mmol) was added. After 12 h, the precipitate was filtered off,
washed with water, and recrystallized from acetonitrile. Yield 54%; mp 235-236°C (acetonitrile). 31P NMR
1
spectrum (dioxane): 56.6 ppm. H NMR spectrum (CF3COOD), , ppm, J, Hz: 2.58 (3H, s, CH3); 3.87 (6H, s,
δ
3
3
N(CH3)2); 7.2 (2H, d, JHH = 7.8, o-CH3C6H4); 7.43 (2H, d, JHH = 7.8, m-CH3-C6H4); 7.9 (5H, br. s+m,
6,7,3',4',5'-H); 8.43 (2H, m, 2',6'-H); 8.87 (1H, s, 4-H). Found, %: N 7.06, 7.11; P 7.75, 7.82. C22H21N2OPS.
Calculated, %: N 7.14; P 7.89.
The 1H and 31P NMR spectra were obtained on a Varian VXR-300.
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