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Synthesis of Pyrazolo Heteroaromatic Compounds by Means of 5-Amino-3-methyl-1-phenylpyrazole-4-carbaldehyde.

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composition, and IR spectrumi3] with the product prepared
from SOClz and HzS,. This new, more productive synthetic
route requires much less time and experimental effort than
the former preparation.
Procedtwe:
Sg (3.76g, 14.7mmol)isdissolved in CHzC12 (800ml)by refluxing. The homogeneous solution is slowly cooled to 0°C and
protected from light by a black cloth. A freshly prepared
solution of trifluoroperacetic acid [obtained by suspension
of 50% H r 0 2 ( l g , 14.7mmol) in CH2C12 (50ml) at 0°C
and rapid addition of trifluoroacetic anhydride ( 5 ml,
36mniol)l is added dropwise over 1 h to the stirred reaction
mixture, which assumes an intense yellow hue. Concentration
in a vacuum at 20°C bath temperature to 1/3 of the original
volume leads to precipitation. Further crystallization is
induced by cooling to -20°C. The precipitate is collected
on a glass frit, washed with CHzC12, and dried in a vacuum.
The procedure yields 1.8g of almost pure S 8 0 which can
be isolated analytically pure by recrystallization from CS2.
Received: May 3, 1974 [Z 67 IE]
German version: Angew. Chem. 86. 648 (1974)
Sulfur-Oxygen Compounds. Part 23.-~-Part22 is considered to he: H .
B a k , 8. Soloirki, P. Rosmus, and R. Sreiidel, Angew. Chem. 85, 987 (1973);
Angew. Chem. internat. Edit. 12, 933 (i973).-.- Part 21: 131.
[2] R. Srrtrilrl and M . Rrhsch, Angew. Chem. 84, 344 (1972): Angew. Chem.
internat. Edit. 11, 302 (1972): R Srriirlri, P. L i y r r , H . Briiilacxk. and M .
Rchwh. ibid. 85. 452 (1973) and 12, 423 (1973). resp.
[ 3 ] R. Slrirdcd and M . RrhsOi, 1. Mol. Spectrosc. 5 1 . 314 (1974).
[I]
Synthesis of Pyrazolo Heteroaromatic Compounds by
Means of 5-Amino-3-methyl-l-phenylpyrazole-4-carbaldehyde
By Jochen Ha@ and Eberhard Breitmaierl']
5-Amino-3-methyl-1 -phenylpyrazole-4-carbaldehyde ( 3 ) is
formed in a modified Vilsmeyer synthesis['.21: reaction of
5-amino-3-methyl-1-phenylpyrazole( I )i31 with an excess of
N,N-dimethylformamide (DMF) and phosphorus oxide
chloride affords crystalline 5-[(N,N-dimethylamino)n~ethyleneamino]-3-methyl-l-phenylpyrazole-4-carba~dehyde (2).
which is converted in good yield into ( 3 ) by acid hydrolysis.
CHS
6:BH5
5-Amino-3-methyl-1 -phenplpyrazole-4-carbaldehyde( 3 ) :
POC13 (1.5mol) is added dropwise with cooling to D M F
(3.5moI). Then ( I ) (0.5mol) is added portionwise, the reaction
mixture is stirred for 17 h at 70°C (oil-bath temperature) and
subsequently poured cautiously into an excess of N a 2 C 0 3
solution (cooling). The crystals that separate after some time
[(Z)] are hydrolyzed by HC1 (ca.2Owt.-%). After 50 hours'
stirring at 40°C (oil-bath temperature), neutralization with
N a 2 C 0 3 solution, extraction with ether and removal of the
solvent, ( 3 ) is obtained as a viscous oil. Recrystallization
from 2-propanol affords a finely crystalline, pale yellow product : yield 64%, m. p. 97.5 "C.
Pyrazolo[3,4-b]p~~ridine
(4)and 6,7-dihydro-3-methyI-6-oxo-lphenylpprazolo/3,4-b]p~~ridine-5-carbonitrile
(5):
The CH-acidic carbonyl compound (0.02 mol) is refluxed with
0.02 mol of ( 3 ) in glacial acetic acid (30 ml) for ca. 30 h. For
working-up, the mixture is poured into an excess of Na,CO,
solution and extracted with ether. The crude products are
recrystallized from ethanol or ethanol/water [(4a), yield 68%,
m.p. 79.5"C; (4b), yield 79%, m.p. 96°C; (4cjL4',yield 46%,
m.p. 86°C; (5), yield SIX, m.p. 316"CI.
3-Methyl-1 -phenylpyrnzolo[3,4-d]p~~rimidine
(6) :
0.025mol of ( 3 ) is heated with 0.1 mol of formamide for
20 h at 140'C. The cooled reaction mixture is treated with
water (10m1)and extracted with chloroform. The oil remaining
on removal of the solvent is crystallized from 2-propanol;
yield 60%, m. p. 84°C.
Received: June I t . 1974 [Z 60 IE]
German versioh: Angew. Chem. 86, 671 (1974)
CAS Registry Numbers:
( I ) : 1131-18-6 1 1 3 ) : 52217-35-3 i ( 4 a ) . 52217-36-4 /
1 4 h ) . 52217-37-5 f ( 4 ~ ) 51431-29-9
:
i (S): 52217-38-6 i
1 6 ) : 52217-39-7 / ethyl 3-oxobutanoate: 141-97-9 1 2,4-pentanedione:
123-54-6 / cyclohexanone: 108-94-1 / ethyl cyanoacetate: 105-56-6 i
formamide' 75-1 2-7.
This new aldehyde opens a direct route for preparation of
condensed heterocycles of the pyrazole series. Thus cyclocondensation of ( 3 ) with 1,3-dicarbonyl compounds affords the
pyrazolo[3,4-b]pyridines (4a)-( 4 c ) , with ethyl cyanoacetate
affords the derivative ( 5 ) and with formamide the pyrazolo[3,4-d]pyrimidine ( 6 ) . The condensation product of ( 3 )
with cyclohexanone is identical with 5,6,7,8-tetrahydropyrazoio[3,4-b]quinoline (4c) prepared from 2-hydroxymethylenecyclohexanone and ( I ) [ " ] . The compounds prepared were
identified by means of spectroscopic data (IR, UV, MS, and
'H- and I3C-NMR).
[*] Dip].-Chem. J . Hlufel and Prof. Dr. E. Breitmaier
Chemisches lnstitut der Universitlt
74 Tiibingen. Auf der Morgenstelle (Germany)
604
[I]
pp.
[2]
[3]
Organikum. V E B Deutscher Verlag der Wissenschaften, Berlin 1970.
358ff
A . Vilsrn~~yer,
Chem.-Ztg. 75, 133 (1951).
E . Mohr, J . Prakt. Chem. 79, 14 (1909).
[4] J . HBi!lel and E. Bueitrnnier, Angew. Chem. 85,959 (1973); Angew Chem.
internat. Edit. 12, 922 (1973).
Conformation of trans-Cyclooctene
By Otto Ermer[*]
Previous X-ray structural studies have not hitherto given exact
structural parameters for trans-cyclooctene derivatives'']
[*] Dr. 0 . Ermer
Abteilung fur Chemie der Universitat
463 Bochum, Universitatsstrasse I50 (Germany)
Angew. Chem. internat. Edit. J Vnl. 13 0 9 7 4 ) J No. 9
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methyl, carbaldehyd, synthesis, pyrazole, compounds, heteroaromatic, mean, amin, phenylpyrazole
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