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Патент USA US2403710

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Patented July 9, 1,946,
2,403,710
j UNITED".-SSTATE1S
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Jaines‘K. Dixon, "Riverside, and J ohn M. Sayward, ‘ ' "
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~ ; Stamford, Conn.,- asslgnorstoAmerican Cyan- v'
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mid Company,:New York, N.,Y., a corporation
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Drawing. 'Application'July 21,1944, '
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Serial No..546,052
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" 6Claims., (01. 2604-2395)
5 The present invention relates. to a newchemical
compound,v 2_-brompyrazine and to a method of
zine hydrobromide, as the case may’ be, are col
lected in the cooler parts of the apparatus. - Upon
preparing the same.-~:
the‘addition of water- to the crystalline distillate,
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,We have discovered that Z-brompyrazine vcan
2¢brompyrazine separates as an oil.
‘be-prepared by heating~.together an .acid salt of
pyrazine and bromine at temperatures up to about
1 .
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> - It is desirable, but'not necessary. to have pres
ent ,at ‘ the ,itimeaof reaction an .inert solvent such
250° C. The formation of mono-brompyrazine in- '
as,‘carbon-‘tetrachloride; a Some of the advan-,
this process involves, webelieve, the preliminary‘
tages of a solvent are-that it aidsin eliminating
formation of a perbromide at relatively low tem
peratures, room temperatures up to about 100° C.,
caking oi the pyrazine salt, makesthe reaction
run smoother, and permits increasing the bromine
usage to nearly 100% of theoretical without in
creasing decomposition. The solvents which we
followed by rearrangement at higher tempera
tures to the corresponding acid salt of 2-brom
pyrazine. The pure 2-brompyrazine may then
can use in our process should have a boiling point
be recovered by methods known to those skilled
below that of brompyrazine and include such inert
in the art. The formation of 2-brompyrazine by 15 solvents as carbon tetrachloride, chloroform, di
our new process may be illustrated in the follow
ing equations:
oxane, benzene, and the like.
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The pyrazine acid salt found best suited for
use in our process is pyrazine hydrochloride,
HHa]
which may be obtained by bubbling hydrogen
/N\
20 chloride through a solution of pyrazine in an or-'
U
ganic solvent. Pyrazine hydrochloride comes
down as a nearly-white, ?uffy precipitate which
can be separated by ?ltration. Other pyrazine
acid salts such as pyrazine hydrobromide may, of
HHal
HHal
N
N\
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——\ -
N
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26
course, be used.
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The preparation of 2,-brompyrazine in accord
_
ijBr + HBr
- N
‘ ~ ance withour invention will now be illustrated
by means of the following speci?c examples,
which, it is understood, are given by way of illus
30 tration and are not intended to limit our process
vto the particular reactants and reaction condi
tions described therein.
Example 1
Br,
The compound z-brompyrazine (mono-brom
pyrazine) is useful as an intermediate in the
preparation of 2-aminopyrazine and in the prep
aration of 2-sulfanilamidopyrazine. It will re
act with para-acetylaminobenzenesulfonamide di
35
Into a 125 cc. stirred ?ask was placed 18 g. of
pyrazine hydrochloride (80% pure==0.124 mol).
Bromine 10.6 g. (0.066 mol) was added to the
rectly to give 2 - p - acetylaminobenzenesulfona
solid pyrazine slowly at about 50° 0., liberating
midopyrazine, whereas the corresponding Z-chlor
heat. The temperature was then raised to 150°
40 C.-165° C. for 1 hour, and then to 190° C. for 1
hour. At this \point vacuum was applied, through
pyrazine does not react to any great extent.
In carrying out our, invention, pyrazine hy
drochloride or pyrazine hydrobromide is treated
at ordinary room temperatures with 50 to 100%
of the theoretical amount of bromine, thereby
forming perbromide.
a side tube and traps. White-to-yellow crystals 7
appeared in the traps while the reaction ?ask
was kept'at 200°-215° C. for about 1.5 hours. The
The perbromide is then 45 product, crude monobrompyrazine, separated as
heated to at least 100° C_.,i'or about one to six
an oil upon addition of water.
hours. Under these conditions rearrangement
occurs whereby the pyrazine ring is'brominated,
releasing hydrogen bromide, and any solvent
present is distilled off. The distillation system is
water and. benzene from-the product gave an oil
then put under a vacuum and the temperature
maintained at 200° C. to about 250° C. for one
21.2 g. (0.132 mol) of bromine was added to’
half to about 4 hours, during which time 2-brom
pyrazine distills from the reaction mass and crys
tals o1 brompyrazine hydrochloride, or brompyra
Distillation of
which was identified as brompyrazine,
Example 2
20.9 g. (80% pure—0.l43 mol) oi.’ pyrazine hydro.
chloride-dissolved in 116 g. of carbon tetrachlo- V
ride. Bromine addition was discontinued after
55 a half hour, when the charge began to darken
2,403,710
3
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3. A method of preparing 2-brompyrazine
whichcomprises mixing together bromine, an in
(temperature about 32° 0.). Upon heating, hy
drogen bromide came o-? at '70 to 80° C. Carbon
tetrachloride was distilled off near 100'’ C. After
one hour crystals began to appear in the con
ert solvent and a halogen acid salt of pyrazine
of the group consisting of pyrazine hydrochloride
and pyrazine hydrobromide and heating the mix
denser tubing (batlr 110° C.) . At15é~° C. carbon
ture at a temperature up» to about 250°C.
tetrachloride was all distilled off and hydrogen
4. A method of preparing Z-brompyrazine
bromide evolution increased temporarily. During
which comprises mixing together pyrazine hy
1.3 hours the bath was raised to 216° C. and more I
drochloride and bromine and heating the mix
crystals appeared. After 20 minutes at 216° C.
a vacuum was applied for 25 minutes; consider 10 ture to a temperature at which Z-brompyrazine
is distilled.
able fog was carried through the traps. An oil,
' 5. A method of preparing 2-brompyrazine
crude mono-brompyrazine, separated.‘ from the
water used to rinse the tubing and traps, To - I which comprises the steps of adding bromine to a
solution of pyrazine hydrobromide dissolved in
prove the'structure of the compound as 2-brom
.pyrazine, it was reacted with alcoholic ammonia 15 an inert solvent, thereafter raising the tempera
ture of the reaction mixture to distill off the inert
‘solvent and continuing the heating under vacuum
and gave a product which compared favorably
with known sample of 2-aminopyrazine. Chem
ical tests were employed to demonstrate the pres.-v
and recovering therefrom z-brompyrazine hydro
ence of vbromine and absence of chlorine, as com
bromide.
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6. A method of preparing 2-brormpyrazine
20
pared with 2-ohlorpyrazine as a control.
which comprises adding» pyrazine hydrochloride
We claim:
to a mixture of bromine and an inert‘ solvent and
thereafter heating the mixture at a temperature
up to about 250° C. for a period of from about
which comp-rises adding bromine and an inert
solvent to a halogen acid salt of pyrazine of the 25 one hour to ten hours whereby 2.-brompyrazine
is formed and recovered as 2-bronrpyrazine hy
group'consisting of pyrazine ‘hydrochloride and‘
1. 2l-birompyrazine.
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2.‘ A method of preparing 2-brompyrazine
pyrazine hydrobromide and heating the mixture
to a temperature at which 2-brompyrazine is dis
tilled.
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drochloride.
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JAMES'K. DIXON.
JOHN M. SAYWARD.
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