Synthesis of new chiral and nonchiral pyrido [3,2-e],[1,3,4] oxadiazine derivatives

Article abstract of DOI:10.1155/2010/791796

A chiral series of 6,7-dichloro-3-[3-(2,2-dihalovinyl)-2,2-dimethylcyclopropyl] -1H-pyrido [3,2-e],[1,3,4] oxadiazines (a-f) and a nonchiral series of 3-substituted, 6,7-dichloro-1H-pyrido [3,2-e][1,3,4] oxadiazines (a-g) have been synthesized. The synthesized compounds were characterized by IR, ¹H-NR, HPLC and mass spectral data.

Full text of DOI:10.1155/2010/791796

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
2010, 7(1), 149-156
http://www.e-journals.net
Synthesis of New Chiral and Nonchiral
Pyrido [3,2-e],[1,3,4] oxadiazine Derivatives
L. S. SHET§*, A. R. SHELAR§ and F. V. MANVI
§Chemistry Department, Shivaji University, Kolhapur, India.
KLE college of Pharmacy, Belgaum, India.
lsshet123@rediffmail.com
Received 29 March 2009; Revised 15 June 2009; Accepted 9 July 2009
Abstract:
A chiral series of 6,7-dichloro-3-[3-(2,2-dihalovinyl)-2,2-
dimethylcyclopropyl] -1H-pyrido [3,2-e],[1,3,4] oxadiazines (a-f) and a
nonchiral series of 3-substituted, 6,7-dichloro-1H-pyrido [3,2-e][1,3,4]
oxadiazines (a-g) have been synthesized. The synthesized compounds were
characterized by IR, 1H-NR, HPLC and mass spectral data.
Keywords: 1H-pyrido, Chiral, Oxadiazine, Phenyl sulfanyl, Naphthyl sulfanyl.
Introduction
Oxadiazines are interesting1 and promising heterocyclic compounds. A diversity of
biological effects is associated with oxadiaxzines bearing hetero atoms at 1, 2, 4 or 1,3,4
positions. 6H-1, 2, 4-oxadiazine-3, 5-(2H, 4H)-dione, the 6-oxa analogue of uracil, has been
shown to significantly inhibit growth in several bacterial strains while not being highly
inhibitory to mammalian cells2.
1, 3, 4-Oxadiazine derivatives exhibit cardiovascular, antibacterial, plant growth regulating,
miticidal and nematocidal, acricidal, insecticidal and anticonvulsive activities3,4. In addition,
oxadiazines are useful intermediates in the synthesis of tenidap prodrugs or β-lactam antibiotics, in
particular into the synthesis of carbapenems and penems5, 6. The invention relates to an optically
active form of a pyridyl-4H-1, 2, 4-oxadiazine derivative7, to the therapeutical use thereof and to a
pharmaceutical compositions containing the compound as active ingredient. More particularly, the
invention relates to the (-) enantiomer of 5,6-dihydro-5-[(1-piperidinyl)-methyl-3-(3-pyridyl)-4H-
1, 2, 4-oxadiazine and its acid addition salts as well as the use of these chemical compounds in the
treatment of vascular diseases. It is reported in literature8 that indoxacarb, an oxadiazine insecticide
blocks insect neuronal sodium channels. Claude Bonnes and co-workers9 reported in their
invention that 3-oxo-5, 6-dihydro-1, 2, 4-oxadiazines useful as antiandrogenic agents. 4-
substituted 5, 6-dihydro-2-o-hydroxyphenyl-4H-1, 3, 4-oxadiazine-5-ones10 were reported
in literature as potential psychopharmacological drugs. The promising therapeutic potential of this
class of compounds prompted us to synthesize novel derivatives of several 1, 3, 4-oxadiazines.

150
L. S. SHET et al.
Scheme 1
Experimental
Melting points were determined on a LABINDIA MR.VIS visual melting range apparatus
and are uncorrected. Reactions monitored by using Shimadzu SPD 10AV HPLC. Solvent
system (mobile phase) acetonitrile –methanol-water (60:30:10) and 240 nm. HPLC column
used was C-18 and flow rate maintained was 1 mL/min. IR spectra in KBR (cm-1) were
1
recorded on Jasco FT/IR-410 series spectrophotometer and H NMR spectra were recorded
(DMSO-d6) on a Bruker 200MHz spectrometer using TMS as internal standard (chemical
shifts are expressed in δppm.). GC-MS spectra were recorded on Polaris Q mass detector.
Chiral pyrido oxadiazine derivatives
6,7-Dichloro-3-[3-(2,2-dibromovinyl)-2,2-dimethylcyclopro- pyl]-1H-pyrido[3,2-e]
[1,3,4] oxadiazine (1R, 3R isomer)(a)
In a set up of 3 necked round bottom flask with magnetic stirrer, 150 mL methanol, 0.05
moles of 3,5,6-trichloropyridin-2-yl (1R, 3R)-3-(2,2-dibromovinyl)-2,2-dimethylcyclo-
propanecarboxylate and 0.5 g PTSA was taken. It was slurry. This mass was cooled to 20 °C
by external cooling and to this 0.055 moles of hydrazine hydrate (80.0% solution) was
added. Addition was exothermic and thin slurry converted into thick white slurry. This was
maintained at 20-30 °C for 4 h. Filtered the mass and washed with 50 mL of methanol. The
hydrazonoate isolated yield was 97.5% .
In a reaction set up of single necked flask, magnetic stirring and oil heating system, 5.0 g
(0.01 mole) of above prepared hydrazonoate, 25 mL dimethyl acetamide (DMAC) solvent and
0.7 g of K2CO3 as acid binder was taken. This was heated to 115-120 °C and maintained for 6
h. Distilled out DMAC under reduced pressure and to the left over residue added water and
filtered. The filtered solid dried and crystallized with 20 mL methanol. Crystallized yield was
65.78%. Off-white crystalline solid; melting point was 180-182°C.
Spectral data
IR (KBr) νmax in cm-1: 3068(C-H str.), 549-662 (C-Br str.), 1462 ( C=C gem. str.)

Synthesis of New Pyrido [3, 2-e],[1,3,4] oxadiazine Derivatives
151
6,7-Dichloro-3-[3-(2,2-dichlorovinyl)-2,2-dimethylcyclopro- pyl]-1H-pyrido [3,2-e]
[1,3,4] oxadiazine. (55:45 cis: trans isomer)(b)
In a set up of 3 necked round bottom flask with magnetic stirrer, 150 mL methanol, 0.05
mole of 3,5,6-trichloropyridin-2-yl-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate
(cis:trans - 55:45) and 0.5 g PTSA was taken. It was slurry. This mass was cooled to 18-20 °C
by external cooling and to these 0.055 moles of hydrazine hydrate (80.0% solution) was
added. Addition was exothermic and thin slurry converted into thick white slurry. This was
maintained at 20-30 °C for 4 h. Filtered the mass and washed with 50 mL of methanol. The
yield of hydrazonoate isolated was 18 g (89.5 % yield).
In a reaction set up of single necked flask, magnetic stirring and oil heating system, 5.0 g
(0.012 mole) of above prepared hydrazonoate, 25 mL dimethyl acetamide (DMAC) solvent
and 0.7 g of K2CO3 as acid binder was taken. This was heated to 115-125 °C and maintained
for 7 h. DMAC was distilled out under reduced pressure and to the left over residue, water was
added and filtered. The filtered solid dried and crystallized with 25 mL methanol. Crystallized
yield was 22.7 %. Off-white crystalline solid; melting point was 258-259 °C.
6, 7-Dichloro-3-[3-(2,2-dichlorovinyl)-2,2-dimethylcyclopro- pyl]-1H-pyrido [3,2-e]
[1,3,4] Oxadiazine (Trans isomer)(c)
Procedure followed for this compound is same as compound (b), but staring ester for this
synthesis was 3, 5, 6-trichloropyridin-2-yl -3-(2, 2-dichlorovinyl)-2, 2-dimethyl cyclopropane-
carboxylate (99.0 % trans isomer). The yield was off-white crystalline solid (12.0 %);
melting point was 236-237 °C.
6,7-Dichloro-3-[3-(2,2-dichlorovinyl)-2,2-dimethylcyclopro- pyl]-1H-pyrido [3,2-
e][1,3,4] oxadiazine (SS isomer)(d)
Procedure followed for this compound was exactly same as compound (b), but staring ester
for this synthesis was 3, 5, 6-trichloropyridin-2-yl (1S, 3S)-3-(2, 2- dichlorovin-yl)-2, 2-
dimethyl cyclopropanecarboxylate (99.0 % SS isomer). The yield of off-white crystalline
solid was 22.0%, melting point was 179-181°C.
Spectral data
IR (KBr) νmax in cm-1: 3068 (-NH str.), 2969 (C-H str.), 1627(C=C aromatic.), 818-847
(C-Cl str.)
1H NMR (DMSO-d6):δ, 1.24(3H,s, CH3), 1.28(3H,s, CH3), 1.73 (1H,d,), 2.01(1H,d),
6.31(1H,d, - vinyl), 7.27 (1H, aromatic), 6.35(1H, s, NH)
GC-MS: 368 (M + 1 peak).

152
L. S. SHET et al.
6,7-Dichloro-3-[3-(2,2-dichlorovinyl)-2,2-dimethylcyclo-propyl]-1H-pyrido[3,2-e]
[1,3,4]oxadiazine (RR isomer)(e)
In a set up of 3 necked round bottom flask with magnetic stirrer, 150 mL methanol, 0.05
moles of 3,5,6-trichloropyridin-2-yl (1R, 3R)-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-
carboxylate and 0.5 g PTSA was taken. It was slurry. This mass was cooled to 15-20 °C by
external cooling and to these 0.055 moles of hydrazine hydrate (80.0% solution) was added.
Addition was exothermic and thin slurry converted into thick white slurry. This was
maintained at 20-30 °C for 4 h. Filtered the mass and washed with 50 mL of methanol. The
yield of hydrazonoate isolated was 89%
In a reaction set up of single necked flask, magnetic stirring and oil heating system,
5.0 g (0.012 mole) of above prepared hydrazonoate and 25 mL pyridine was taken and heated
to reflux at 115-116 °C and maintained for 6 h. Pyridine was distilled out under reduced
pressure and to the left over residue 50 mL dichloromethane solvent +50 mL water was added.
Separated layers and organic layer washed with 25 mL of dilute sodium carbonate solution
followed by water. Organic layer concentrated and crystallized with 10 mL of isopropyl
alcohol. The yield of off-white crystalline solid was 34%, melting point was 160-162 °C.
6,7-Dichloro-3-[3-(2,2-dichlorovinyl)-2,2-dimethylcyclopro- pyl ]-1H-pyrido[3,2-
e][1,3,4] oxadiazine (RR + SS - isomer)(f)
Synthesis procedure remains same as compound (e), but only change is that starting ester is 3,
5, 6-trichloropyridin-2-yl-3- (2,2-dichlorovinyl)-2,2-dimeth- yl cyclopropane carboxylate (RR
+ SS isomer). The yield of off-white crystalline solid was 35%, melting point was 147-148 °C.
Nonchiral pyrido oxadiazine derivatives
6,7-Dichloro-3-{[(2,5-dichlorophenyl)sulfanyl]methyl}-1H-pyrido [3,2-e][1,3,4]
oxadiazine(a)
In a set up of single necked round bottom flask with magnetic stirrer, 50 mL of methanol, 0.006
moles of 3,5,6-trichloropyridin-2-yl [(2,5-dichlorophenyl) sulfanyl] acetate and 0.1g PTSA was
taken. It was slurry. This mass was cooled to 18-20 °C by external cooling and to these 0.007
moles of hydrazine hydrate (80.0% solution) was added. Addition was exothermic and thin
slurry converted into thick white slurry. This was maintained at 20-30 °C for 4 h. Filtered the
mass and washed with 50 mL of methanol. The yield of hydrazonoate yield was 93.0 %.
In a reaction set up of single necked flask, magnetic stirrer and oil heating system, 2.0 g
(0.005 mole) of above prepared hydrazonoate, 25 mL DMAC solvent and 0.23 g of K2CO3
was added as acid binder. This was heated to 140-145 °C and maintained for 4 h.
DMAC was distilled out under reduced pressure and to the left over residue water was
added and filtered. The filtered solid dried and crystallized with 100 mL methanol, as solubility is
very poor. The yield of buffer-white crystalline solid was 74%, melting point was 211-212 °C.

Synthesis of New Pyrido [3, 2-e],[1,3,4] oxadiazine Derivatives
153
Spectral data
IR (KBr) νmax in cm-1: 3209 (-NH str.), 3045 (C-H str.), 1607(C=C aromatic.), 801-843 (C-
Cl str.)
1H NMR(DMSO-d6): δ, 3.31(2H, s, CH2), 6.95(1H, s, NH) 7.21-7.59 (4H, aromatic).
6,7-Dichloro-3-{[(2,4,5-trichlorophenyl)sulfanyl]methyl}-1H -pyrido [3,2-e][1,3,4]
oxadiazine (b)
Synthesis procedure remains same as compound (a), but starting ester is 3, 5, 6-
trichloropyridin-2-yl [(2, 4, 5-trichlorophenyl) sulfanyl] acetate. The yield of crystalline solid
was 70%, melting point was 212-213 °C.
Spectral data
IR (KBr) νmax in cm-1: 3205 (-NH str.), 3038 (C-H str.), 1605(C=C aromatic.), 804-841 (C-
Cl str.)
1H NMR(DMSO-d6):δ, 3.01 (2H, s, CH2), 7.41(1H, s, NH) 7.21-7.59 (3H, aromatic)
6,7-Dichloro-3-[(naphthalene–1-yl-sulfanyl)methyl]-1H-pyrido[3,2-e][1,3,4]
oxadiazine(c)
Synthesis procedure remains same as compound (a) above but starting ester is 3, 5, 6-
trichloropyridin-2-yl (1-naphthylthio) acetate. The yield of crystalline solid was 65%, melting
point was 133-134 °C.
6,7-Dichloro-3-(4-chlorophenyl)-1H-pyrido[3,2-e][1,3,4] oxadiazine (d)
Synthesis of 3,5,6-trichloropyridin-2-yl 4-chlorobenzoate
To 1 necked 250 mL round bottom flask, 50 mL dichloromethane solvent and TBAB catalyst
was taken and then to this 21.5 g (0.1 mole) of ammonium salt of 3,5,6-trichloro –pyridine-2-
ol was added. It was stirred using magnetic stirrer. It was thin white slurry. To this, 19.25 g
(0.11 moles) of 4-chloro benzoyl chloride was added slowly over 15 minutes. The addition of
acid chloride was exothermic and hence temperature was controlled at 30-42 °C. After
addition of acid chloride, reaction mass becomes thin with fine salt (ammonium chloride)
precipitation. Further reaction was maintained at 40-42 °C for 4 h. To this mass 100 mL of
water was added and stirred. Separated layers and organic layer washed with 50 mL of 5%
Na2CO3 solution to remove any unreacted acid part. Organic layer further washed with water
and dried over CaCl2. Product in dichloromethane solvent was concentrated to below 50 °C to
remove solvent part and crude product re-slurried with 100 mL methanol was filtered. The
yield of white crystalline solid was 92%, melting point was 118-119 °C.
The reaction with hydrazine hydrate to hydrazonoate was remains same as compound (a).
Cyclization of hydrazonate intermediate to 6, 7-dichloro-3-(4-chlorophenyl)-1H-pyrido [3,2-
e][1,3,4] oxadiazine remains same as that we followed in the compound (a). The yield of white
crystalline solid was 61%, melting point was 173-175 °C.

154
L. S. SHET et al.
Spectral data
IR (KBr) νmax in cm-1: 3283 (-NH str.), 2983 (C-H str.), 1595(C=C aromatic.), 827-855 (C-
Cl str.).
1H NMR(DMSO-d6):δ, 7.27(1H, s, NH) 7.43-7.78 (5H, aromatic).
GC-MS: 317 (M + 1 peak).
6,7-Dichloro-3-methyl-1H-pyrido [3,2-e][1,3,4] oxadiazine(e)
Synthesis of 3,5,6-trichloropyridin-2-yl acetate
To 1 necked 100 mL round bottom flask, 50 mL dichloromethane solvent, DMAP catalyst
was taken and then to this 16.0 g. (0.075 mole) of ammonium salt of 3,5,6-trichloro –
pyridine-2-ol was added . It was stirred using magnetic stirrer. It was thin white slurry. To
this 7.06 g (0.09 moles) of acetyl chloride was slowly added over 5 minutes. The addition of
acid chloride was exothermic and hence temperature controlled between 30-42 °C. After
addition of acid chloride, reaction mass becomes thin with fine salt (ammonium chloride)
precipitation. Further reaction was maintained between 40-42 °C for 4 h. To this mass 50
mL water was added and stirred. Separated layers and organic layer washed with 25 mL of
5% Na2CO3 solution to remove any unreacted acid part.
Organic layer further washed with water and dried over CaCl2. Product in
dichloromethane solvent was concentrated to below 50 °C to remove solvent part and crude
product was re-slurried with 50 mL methanol and filtered. The yield of white crystalline
solid product was 77.7%.
The reaction with hydrazine hydrate to hydrazonoate remains same as compound (a). In a
reaction set up of single necked flask, magnetic stirring and oil heating system, 5.0 g (0.02
mole) of above prepared hydrazonoate, 25 mL pyridine was added heated to reflux at 115-116
°C and maintained for 6 h. Pyridine was distilled out under reduced pressure and to the left
over residue 50 mL dichloromethane solvent + 50 mL water was added. Separated layers and
organic layer washed with 25 mL of dilute sodium carbonate solution followed by water.
Organic layer concentrated and crystallized with 10 mL of isopropyl alcohol. The yield of off-
white crystalline solid was 68.8%, melting point was 173-174 oC.
6,7-Dichloro-3-(2-chlorophenyl )-1H-pyrido[3,2-e][1,3,4] oxadiazine (f)
Synthetic procedure was remains same as (d). The yield of off-white crystalline solid was
65.5%, melting point was 175-177 oC.
6,7-Dichloro-3-phenyl -1H-pyrido[3,2-e][1,3,4] oxadiazine (g)

Synthesis of New Pyrido [3, 2-e],[1,3,4] oxadiazine Derivatives
155
In a one necked 250 mL round bottom flask, 50 mL of dichloromethane solvent, TBAB
catalyst was taken and then to this 10.8 g (0.05 mole) of ammonium salt of 3,5,6-trichloro –
pyridine-2-ol was added. It was stirred using magnetic stirrer. It was thin white slurry. To
this 7.8 g (0.55 moles) of benzoyl chloride was added slowly over 15 minutes. The addition
of acid chloride was exothermic and hence temperature controlled between 30-42 °C. After
addition of acid chloride, reaction mass was becomes thin with fine salt (ammonium
chloride) precipitation. Further reaction was maintained between 40-42 °C for 4 h. To this
mass 100 mL water was added and stirred. Separated layers and organic layer washed with
40 mL of 5% Na2CO3 solution to remove any unreacted acid part. Organic layer further
washed with water and dried over CaCl2. Product in dichloromethane solvent was
concentrated to below 50 °C to remove solvent part and crude product re-slurried with 100
mL methanol and filtered. The yield of white crystalline solid was 93.9%.
In a set up of one necked 50 mL round bottom flask with magnetic stirrer, 25 mL
methanol, 0.013 moles of 3,5,6-trichloropyridin-2-yl benzoate and 0.1 g PTSA was added. It
was slurry. This mass was cooled to 18-20 °C by external cooling and to these 0.015 moles
of hydrazine hydrate (80.0% solution) was added. Addition was exothermic and thin slurry
converted into thick white slurry. This was maintained at 20-30 °C for 4 h. Reaction mass
concentrated under reduced pressure at 45-50 °C. To this concentrated product 25 mL of
pyridine was added and refluxed for 6 h. Then pyridine was distilled out under vacuum at
100-105 °C. To the residual part, water was added and filtered the product. The isolated
crude product purified in 25 mL of methanol. The yield of buffer white solid was 62%,
melting point was 175-177 oC. GC-MS: 283 (M + 1 peak).
Results and Discussion
The chiral acid mixture (3-(2, 2-dihalovinyl)-2,2-dimethyl cyclopropane carboxylic acid)
used in the synthetic process was obtained from M/s Gharda Chemicals Ltd. The chiral
mixture was resolved to get single isomer as well as recemic mixture for experimental
purpose. The isolated acid was converted into acid chloride by reacting with thionyl chloride
under controlled condition to preserve chiral purity. The input raw material i.e. 3,5,6-
trichloropyrine-2-ol was obtained from M/S Gharda Chemicals Ltd. This 3,5,6-
trichloropyrine-2-ol (198.5 g, 1.0 mole) was taken in 500 mL methanol solvent and dry
ammonia gas at 30-35 °C was passed till ammonical pH. This was further refluxed for 1.0 h
and then filtered at 30 °C to get ammonium salt. 3,5,6-trichloropyridin-2-yl-3-(2,2-
dihalovinyl)-2,2-dimethylcyclopropanecarboxylate was prepared by reacting corresponding
acid chloride with 3,5,6-trichloropyrine-2-ol ammonium salt in dichloromethane solvent in
presence of DMAP catalyst at 40 °C. The quantity of ammonium salt taken was 10 mL
excess than acid chloride and dichloromethane solvent was 100 mL per 0.05 mole scale.
Similarly other carboxylates and sulfanyl acetates were prepared. Reacting 0.05 moles of
these intermediate in 50 mL methanol and 0.055 moles of 80% hydrazine hydrate at 20 °C
using PTSA catalyst, prepared the corresponding hydrazonoates. The novel derivatives of
synthesized oxadiazine likely to show diverse biological activity.
Acknowledgement
The author wishes to express their sincere thanks to Dr.K.H.Gharda, Chairman & Managing
Director of Gharda Chemicals for his continuous encouragement and also to utilize the
chemicals and other facility. We are also thankful to Shivaji University Kolhapur and the
management of KLE college of Pharmacy for their support to complete this research work.

156
L. S. SHET et al.
Thanks are also due to Dr.K.Sonawane & Dr. Kishor Bhat for providing spectral analysis
and antibacterial study respectively. The author also wishes to mention thanks to
Mr.D.K.Shenoy & Mr. Vidyasagarn for their support.
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