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An Unusual Diazo-Coupling Reaction.

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285 mp, E = 12,500 (in alcohol); the aldehyde gives a 2,4-dinitrophenylhydrazone perchlorate, m.p. = 319 "C (from 50 %
acetic acid). As with the 4-aldehyde, it does not undergo the
benzoin or Cannizzaro reaction, giving instead intractable
brown, tarry products.
I-Benzylimidazole-2-carbaldehyde(2b) (b. p. 128 'C/4 mm
Hg), prepared similarly, gives the usual carbonyl reactions,
affording a n oxime, m.p. 167'C (from alcohol), semicarbazone, m.p. 196 "C (from dilute alcohol), phenylhydrazone, m. p. 169 "C (from alcohol), 2,4-dinitrophenylhydrazone perchlorate, m.p. 228 "C (from alcohol), and
hydrochloride, m. p. 142 "C (from dilute HC1). The benzoin
condensation occurs smoothly in alcoholic solution, giving
pale yellow l,l'-dibenzyl-2,2'-imidazoloin, m. p. 140 "C,
whose 1R spectrum confirms the ene-diol structure expected
by analogy with pyridoin [41. The imidazoloin is oxidized in
boiling dioxane by a current of air to the almost colorless
diketone I,l'-dibenzyl-2,2-oxalyldiimidazole, m.p. 148 OC.
Received: June loth, 1966 [Z 263 I€]
German version: Angew. Chem. 78, 715 (1966)
[ I ] F. L. Pymnn, J. chem. SOC.(London) 109, 186 (1916).
[ 2 ] Z.Horii, K . Sakurai, K . Toniino, and T. Konishi, J. pharrnac.
SOC.Japan 76, 1102 (1956); Chem. Abstr. 51, 3553b (1957).
[ 3 ] M . Hnrfertist, A . Bnvley, and W. A. Lazier, J. org. Chemistry
19, 1608 (1954).
[4] H. R. Herisel, Angel+. Chcm. 65, 491 (1953).
organic solvents (e.g. o-dichlorobenzene or nitrobenzene) at
100-150 "C. The solution, initially clear and colorless, soon
becomes colored and the dye (3) usually crystallizes during
the reaction.
This reaction is of interest for preparation of azo dyes
containing only partially substituted carboxamide groups
adjacent to the azo group, since such dyes are not accessible
by normal diazotization and coupling.
The structures of the products were proved by degradation.
Received: May 13th, 1966
[Z 238 IE]
German version: Angew. Chem. 78, 673 (1966)
[ I ] A. Weddige and H . Finger, I. prakt. Chem. 35, 262 (1887).
Alkylations by Dialkoxycarbonium Salts
By Dr. S. KabuB
Chemisches Laboratorium, Universitat Freiburg (Germany)
Dedicated to Prof: A . Liittringhaus on his 60th Birthday
Dialkoxycarbonium ions [as in ( I ) ] [11 are typical ambident
cations [21 which, according to the reaction conditions, react
with nucleophiles either in a kinetically controlled reaction
to give orthoacid derivatives (2) or in a thermodynamically
controlled reaction&with _dealkylation to give carboxylic
esters (3).
An Unusual Diazo-Coupling Reaction
By Dr. W. Kullick
Azo-Laboratorium,
Farbenfabriken Bayer AG., Leverkusen (Germany)
Dedicated to Prof. A . Liittringhaus on his 60th birthday
On diazotization of anthranilamides whose amide group is
not fully substituted, benzo-1,2,3-triazin-4-ones( I ) "1 are
formed, which d o not undergo diazo coupling in a n aqueous
medium.
Opening of the triazinone ring and coupling to yield azo
dyes can, however, be achieved by heating ( I ) with 3hydroxy-2-naphthamides (2) or acetoacetamides in polar
In alkylation reactions ( I ) -+ (4) the ester molecule (3) is
the leaving group. Since replacement reactions occur the
easier the more weakly basic is the leaving group, we should
expect that dialkoxycarbonium salts ( I ) , like trialkyloxonium
salts, would be very strong alkylating agents, able to react by
transalkylation with even weak nucleophiles.
X
Carbonium
salt
Alkylation product X+SbC16-; X+ :
*
c=0
I
NHR
M . p . ("C)
Yield
( %)
-
131 - 132
95
91
166-168
97
123--125
92
72-14
90
61
129 [a]
87
122 [a]
90
133 [a]
91
I30 [a]
91
65-68
92
72-75
62
[a] With decomposition.
131, M.P.
R
H
CsHs
2-CH3-4-NHAc-CgHs H
~ - C H ~ - ~ - C I - C ~ H JH
5-CONH-CsHs
C6Hs
5x1
C6H5
C6Hs
4,6-Clz
o-CH3-CnH4
5,6-CO-CsH4-o-CO-
2-CH3
287-289[a1
2 - 0 ~ ~ ~ 257-258[a1
5-CI-2,4-(OCH3)2 242-244[a]
2-CH3
294-296
2-OCH3
27,-274[al
2-OCH3
266--268[a]
4-C1
245-247[a]
2-OCH3
310-312
Angew. Chem. internat. Edit. J Vol. 5 (1966) J No. 7
Experiment confirmed this expectation. Dialkylamides, sulfoxides, ethers, aldehydes, and ketones are alkylated to the
corresponding salts by dialkoxycarbonium salts, the reactions being quantitative and often very fast (31. Even esters of
higher carboxylic acids can be alkylated in good yield if they
are added in excess and if the lower-boiling ester is removed
from the equilibrium mixture.
Dialkoxycarbonium salts are among the strongest alkylating
675
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