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Cyclization of Azomethines by N-Chlorocarbonyl Isocyanate.

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(750 ml), and triethylamine (25 g, 0.25 mol) is added dropwise over 30 min. The temperature is kept at 25-30°C by
cooling in ice. After 1.5h the precipitate is filtered off,
affording (31 (160 g, 70%) as golden-red crystals, which
after recrystallization from dimethylformamide melt at
253 "C with decomposition.
chloride o r phosgene into the corresponding isocyanates,
the analogous reaction with ureas has not previously been
recorded. We have now prepared isocyanates of type ( 3 )
(water-clear distillable liquids) by a simple method, namely
addition of N-chlorocarbonyl isocyanate [2)[41to Schiff
bases ( I ) .
Ar-CH=K-R
4-Cyano-7,8-dimethyl-2-o.xo-I,2,4-oxadiaiolo[2,3-a]quinoxaline 5-oxide (4):
( 3 ) (230 g, 1 mol) is suspended in chlorobenzene (2 I), and
a vigorous stream of phosgene is passed through the suspension a t 8 G 9 O o C , whereupon the color changes from
red to yellow. The reaction is complete when addition of
a sample of the yellow precipitate to water no longer produces a red color. On filtration, yellow crystals of (4)
(239 g, 93%) are obtained, which after recrystallization
from DMSO melt at 228°C with decomposition.
4-lrnirro-7,8-dimethy(ben~o~teridine
SJO-dioxide (5) :
( 4 ) (25.6 g, 0.1 mol) is suspended in dimethylfomamide
(1 50 ml) and treated with concentrated ammonia solution
(20 g). After 8 h, filtration affords yellowish-brown crystals
of (5) (25 g, 92%), which after recrystallization from dimethylformamide melt at 360°C with decomposition.
7&Dimethylbenzopteridine 5,IO-dioxide ( 6 ) :
( 5 ) (27.3 g, 0.1 mol) is stirred in 20% sulfuric acid (300 ml)
for 8 h at 80°C. Filtration then affords yellow crystals of
(6) (21.5 g, 77%).
7,8-Dimethylbenzopteridine( 7 ) . lumiclzrome
(6) (27.4 g, 0.1 mol) is suspended in methanol (200 ml) and
treated at 70°C dropwise with a solution of sodium dithionite (60 g) in water (210 ml). After 5 h the mixture is
cooled and filtered. The precipitate isolated is stirred with
water, thus affording lumichrome ( 7 ) as yellow crystals
that, after recrystallization from glacial acetic acid, melt
with decomposition at 354°C (Ref. [3], 360°C).
Received: May 23. 1972 [Z 680c IE]
German version : Angew. Chem. 84,1061 (1972)
Publication delayed a t authors' request
[ l ] K. Lev. F Seng. R. Nast. U . Eholzer., and R. Schubarr, Angew.
Chem. R I . 569 (1969); Angew. Chern. internat. Edit. 8, 596 (1969).
[Z] F . Seng, R. Nast, and K. Ley, Ger. Pat. Appl. P 16-70-743,O
(Aug. 26. 1966); DOS 1670743.
131 R. Kuhn, Chem. Ber. 67. 1826 (1934).
141 F. B. Mallor?... S L. Manor!. and C S. Wood. J. Amer. Chem.
SOC.87. 5433 (1965).
+ C1-CO-NCO
~Ar
Ar-FH-r-R
c1 c=o
I
( 21
( 1)
13)
+
xco
______
R
B p YCjtorr3
(3)
Yield
Y4]
In ( 3 ) the basic character of the amide nitrogen is weakened
by the neighboring chlorine atom, which would be expected to contribute significantly t o the stability of such
N-carbonylureas. The reactivity towards acylatable compounds is comparable with that of alkoxycarbonyl isocyanates['I.
The structures of the compounds obtained are proved by
their IR spectra [stretchingvibrations at 1700cm-' (C=O)
and 2242 cm-I (N=C=O)], NMR spectra, results of
elemental analysis, and chemical reactions.
Experimental:
N-Chlorocarbonyl isocyanate (2) (105.5 g, 1 mol) in
chlorobenzene (250 ml) is treated dropwise over 45 min at
IS-30°C with the Schiff base (119 g, 1 mol) from benzaldehyde and methylamine. The whole is stirred at cu. 25 "C
for 3 h, then the chlorobenzene is removed at water-pump
pressure and the residue is distilled at oil-pump vacuum.
This affords (3a) (148 g, 66%) as a colorless oil of b.p.
112"C/0.05 torr.
Received: May 23. 1972 [Z 680d IE]
German version: A R ~ ~Chem.
w . 84,1062 (197-7)
Publication delayed a t authors' request
[I] A . J . Speziale and L. R. Smith, J . Org. Chem. 27, 3742 (1962).
[2] A. 1. Speziaie, L. R. Smith, and J . E. Fedder, J . Org. Chem 30.
4306 (1965); W . Kleberr and E. Miiller. DOS 1518 806 (Aug. 21. 1969).
Farbenfabriken Bayer AG.
131 L. J . Samaraj. N A . Bondor. and G.J. Derkarsch, Angew. Chem. 7'9.
897 (1967), Angew. Chem. internat. Edit. 6. 864 (1967)
141 H. Hagemann, Angew. Chem. 83, 906 (1971); Angew. Chem.
internat. Edit. 10. 832 (1971).
Cyclization of Azomethines by
N-Chlorocarbonsl Isocyanate
N-Carbonylureas from Azomethines and
N-ChIorocarbonyl Isocyanate
By Hermann Hagernann and Kurt Ley"'
By Hermunn Hagemann and Kurt Ley"]
Dedicated to Professor Otto Buyer on the occasion of his
70th birthday
Although it is known that carboxamides"', carbamidic
esters[*', and carbamidamide~[~I
are converted by oxalyl
Schiff bases from aromatic aldehydes add N-chlorocarbonyl isocyanate[" with retention of the isocyanate
group[']. The products, of type (Z), are formed also on
treatment of azomethines ( I ) with N-chlorocarbonyl
isocyanate.
[*] Dr. H . Hagemann and Prof. Dr. K . Ley
Wissenschaftliches Hauptlaboratorium der Farbenfabriken
Bayer AG
509 Leverkusen-Bayerwerk (Germany)
[*I Dr. H. Hagemann and Prof. Dr. K . Ley
Wissenschaftliches Hauptlaboratorium der Farbenfabriken
Bayer A G
509 Leverkusen (Germany)
Dedicated to Professor Otto Bayer on the occasion of his
70th birthday
Afigen'. Chem. internor. Edit.
1 Vol. I 1 (1972) No. 11
1011
":B
,CH-C-N-R1
s
H
+ CI-C-N=C=O
-+
I
R2
(2)
(1)
R'
H
H
(3)
(4)
R2
R3
( a ) cyclohexyl CH3
CH3
( b ) cyclohexyl -CHz-CH=CH-(CHz)z-
CH3
CH3
( e ) benzyl
if) i-C3H7
(c)
(d)
CH3
CH3
-CHz-CH=CH-(CHZ)zCH,
CH3
CH3
CH3
within wide limits[']. Only little is known about six-membered representatives of this class of compoundr2].We obtained ( 3 ) , a derivative of imidodicarboxylic acid, by
treatment of N-chlorocarbonyl isocyanate[31with trisubstituted thioureas ( I ) and dehydrochlorination of the
salt-like compounds (2) first formed.
R:
I
,,cH-c-N-R'
I
ClC=O
i
N=C-0
131, m.p
Reservations may be made about the aromatic character
of ( 3 ) ,as for the five-membered mesoionic aromatic compounds of type (4)[4.11. The photoelectron spectra['] of (3)
rcl
198
21 1
205-207
190
86-88
161-163
(3), yield
92
91
57
44
70
78
rL1
-___
(41, m.p. C"C1 (41, yield
213
213
180
192
204
203
92
98
66
60
39
92
C"L1
-
The reaction of derivatives of disubstituted acetaldehyde
does not stop at the isocyanates (Z), but on gentle warming
(ca. 90°C) a rapid cyclization occurs, yielding 6-chloropyrimidine-2,4-diones ( 3 ) .
Like the open-chain analogs131,these heterocycles are
readily substituted by nucleophiles at carbon atom 6:
heating with water or aqueous ethanol leads smoothly
to ( 4 ) .
The structures of the products are proved by IR and NMR
spectra and the results of elemental analysis.
Experimental:
A solution of the aldimine (153 g, 1 mol) from isobutyraldehyde and cyclohexylamine in chlorobenzene (600 ml) is
added dropwise at 20-30°C (cooling) to a solution of
N-chlorocarbonyl isocyanate (105.5 g, 1 mol) in chlorobenzene (200 ml). The mixture is kept at room temperature for
2 h, then stirred for a further hour with gradual warming
to 90°C. Most of the product then separates. After cooling,
compound (3a) is obtained as colorless crystals (190 g),
melting at 198°C. A further crop (47 g) of (3a) can be
isolated from the mother liquor.
(3f) (100 g, 0.46 mol) is recrystallized from water (500 ml).
This affords the dihydrobarbiturate (4f)(84 g, 92%) melting at 203°C.
-____
Received: May 23,1972 [Z 680e IE]
German version: Angew. Chem. 84,1063 (1972)
Publication delayed at authors' request
[I] H . Hogernann and K . Ley, Angew. Chem. 84,1062(1972); Angew.
Chem. internat. Edit. 11, 1011 (1972).
[2] H . Hugernann, Angew. Chem. 83, 906 (1971); Angew. Chem.
internat. Edit. 10, 832 (1971).
[ 3 ] a) E. Cherbuliez and E. Feer, Helv. Chim. Acta 5, 678 (1922);
b) H . Hellrnann, Angew. Chem. 69,466 (1957).
R
R
(3)
1 3 ~ )R. = C H I , m.p. 210-211 "C
( 3 b ) , R = i-C3H,, m.p. 190°C
(3c). R = n-C,H,, m.p. 114°C
( 3 d i . R = cyclohexyl, m.p. 208°C
show two signals for the three N atoms in the intensity
ratio 2 : 1 [= (number of N atoms with positive partial
charge) :(number ofN atoms with negative partial charge]],
whereas the four nitrogen atoms of a monothiotriuret of
type (6a) give only one signals. This finding shows the
strong charge separation typical of mesoionic heterocycles.
Heating an aqueous solution of (3a) to the boiling point
leads, with ring opening, to the monothiobiuret (Ja),m. p.
Six-Membered Mesoionic "Aromatic" Compounds
By Hermann Hagemann and Kurt Ley[*]
Dedicated to Professor Otto Bayer on the occasion of his
70th birthday
The position and nature of the hetero atoms in five-membered mesoionic compounds of sydnone type can be varied
[*I
Dr. H. Hagemann and Prof Dr. K. Ley
Wissenschaftliches H;I iipilaboratorium der Farbenfabriken
Bayer AG
509 Leverkusen-Bay erwerk (Germany)
1012
0
I1
:
:
CH3
Angew. Chern. internat. Edit.
c1
/ Val. I 1
(1972)
/ No. I 1
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azomethines, isocyanates, cyclization, chlorocarbonyl
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