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Cycloadditions of Ketenes to Ynamines.

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Cycloadditions of Ketenes to Ynamines
CH3
I
By M . Delaunois and L. GhosezI*l
The cis-stereospecific formation of cyclobutanones
from
ketenes and olefins, dienes, and vinyl ethers proceeds via a
onestep multicenter cycloaddition. The reaction of ketenes
with enamines, however, follows a different path involving
a dipolar intermediatec21.
We have found that ketenes react readily with ynamines
even at very low temperatures. Herezalsoithe cycloaddition
apparently proceeds through the formation:of a zwitterionic
intermediate [31.
(a), R'
(6). R'
(a), R~ = C ~ H ~
(61, R2 = N(CzH5)z
(c), R 2 = CH3
= C~H,
= H
(9). R'
(lo). R'
(If).
= CsH5. R 2 = CH,
(S), R1 = R 2 = CsH5
= H, R 2 = CH,
(6). R'
(7), R'
R' = H, R 2 = CsH5
I
Reaction
I
(a),
Yield
(%)
M.p. ( "C)
B.P. ("Cltor
188.5
147
(Ib) f ( 2 4
(by product)
+
(8)
78
7 [cl
96
(Ib) 4-(2c) + (10) 83
(main product)
( I b ) -t (2ai + ( 1 1 )
(by product)
9 tcl
72.2
1735
1609
1580
1738
1578
2.62 (15H)M
6.63 (4H) M
8.95 (3H) T
9.51 (3H) T
2.72 (10H) S
6.55 (4H) Q
7.1 (4H) Q
1728
1578
132"C/0.7
1740
1580
78
1940
1610
15-55/0.7
1955
1625
!40/0.5
1942
8'92 (1 2H)
9.15
(T in both
cases)
2.8 (5H) M
6.62 (4H) Q
6.89 (2H) S
8.85 (6H) T
-
2.72 (10H) S
6.78 (4H) Q
7.93 (3H) S
9.09 (6H) T
5.18 (2H) Q
6.6 (4H) Q
8.15 (3H) T
8.87 (6H) T
-
[b] T values; Varian A-60, CC14 solution (except for (5) which was
dissolved in CDCI,), TMS as internal standard.
Icl Determined by gas chromatography.
The addition of diphenylketene (fa) t o a n ethereal solution
of N,N-diethylphenylethynylaminef2a) or bis(N,N-diethylamino)acetylene (2b) at -50 O C leads to almost quantitative
formation of cyclobutenones ( 5 ) and ( 6 ) respectively. The
structure determination was based on I R and N M R findings.
The reaction product from diphenylketene ( I ) and N,Ndiethylpropynylamine (Zc), however, was shown to be the
allenic amide (9) whose constitution was proved by an independent synthesis (41 from diphenylketene and the phosphonium ylid (12).
72
= CsH5, R 2 = N(CzH5)z
= H, R 2 = CsH5
R' = H, R2 = CH3
N M R [b]
}
(Ib) f ( 2 4 --j (7
(main product)
When the ketene ( I b ) was treated with (2a) under the same
experimental conditions, the crystalline cyclobutenone ( 7 )
was isolated in 78 % yield. Examination of the mother liquor
showed a small amount of allenic amide (111 which was
isolated by preparative gas chromatography (carbowax
20 M). With (2c), however, the liquid allenic amide (10)
was the major product. Its constitution was proved by independent synthesis from the ylid ( / 2 ) and acetyl chlo-
ride 141. Theminor constituent was purified by gas chromatography and characterized as the cyclobutenone (8).
We think these results are best explained by a multistage
process involving the formation of the resonance-stabilized
zwitterion (3) as first step. This intermediate could then
cyclize in two ways leading either t o a cyclobutenone ( 5 ) to
(8) or to an oxete ( 4 ) 151 which would rapidly rearrange to
the corresponding allene.
Preparation of 3-dimethylamino-2,4,4-triphenylcyclobut-2-enI-one ( 5 )
Diphenylketene ( l a ) (2.7 g, 0.014 mole) is added dropwise at
-50 "C to a solution of (2a) (2.5 g, 0.014 mole) in dry ether
(25 ml). After 2 h at -50 O C the reaction is slowly warmed to
room temperature (1 h). The precipitate is filtered off and
recrystallized from pentane. Yield 4.8 g (95 %) of ( 5 ) .
Preparation of N,N-diethyl-I-methyl-I-allenecarboxamide
(10)
An ethereal solution of ( I b ) (0.75 g, 0.018 mole) is added
dropwise at -6OOC to a solution of (2c) (2 g, 0.018 mole) in
dry ether (25 ml). After 80 min at -6O"C, the mixture is
slowly warmed to room temperature. Evaporation of the
solvent and distillation gave 2.19 g (83 %) of (10) as a yellow
liquid, b.p. 45-55 OC10.7 torr as well as 0.19 g (7 %) of 181,
b.p. 132 'C/0.7 torr, purified by preparative gas chromatography (Carbowax 20 M).
Received: November 4, 1968
[ Z 899 IE]
German Version: Angew. Chem. 81,33 (1969)
I*]
M. Delaunois and Prof. L. Ghosez
Laboratoire de Chimie Organique de Synthese
Universite de Louvain
96, Naamsestraat, Louvain (Belgium)
111 R . Huisgen, L . Feiler, and G. Binsch, Angew. Chem. 76, 892
(1964); Angew. Chem. internat. Edit. 3, 753 (1964); G . Binsch,
L. Feiler, and R. Huisgen, Tetrahedron Letters 1968,4497; J . C.
Martin, V. W. Goodlett, and R. D . Burpitt, J. org. Chemistry 30,
4309 (1965); R. Montaigne and L . Ghosez, Angew. Chem. 80,
194 (1968);Angew. Chem. internat. Edit. 7, 221 (1968); R . Montaigne, Dissertation, Louvain (1968).
Angew. Chem. internat. Edit. 1 Vol. 8 (1969) / No. I
[2] P. Otto, L . A . Feiler, and R. Huisgen, Angew. Chem. 80, 759
(1968); Angew. Chem. internat. Edit. 7, 737 (1968).
[3] For related reactions leading to allene amidinium salts and
cyclobutenecyanine see H. G. Viehe, R. Buyle, R . Fuks, R . Merenyi, and J. M . F. Uth, Angew. Chem. 79, 53 (1967); Angew.
Chem. internat. Edit. 6, 77 (1967); B. Huveuux, Dissertation
Louvain (1968).
[4] H . J . Besttnann and H . Hurtung, Chem. Ber. 99, 1198 (1966).
[S] The two-stage cycloaddition of bis(trifluoromethy1)ketene
to olefins also occurs across the C=C or C=O double bonds of
the ketenes (D.C. Englond and G. C. Krespun, personal communication).
Disulfene
lized from methanol. (3) decomposes at 210 "C with discoloration. Its IR spectrum contains only four bands, at 1375
(SO2 asym.), 1155 (SO2 sym.), 825, and 695 cm-1.
The most striking property of the disulfene (1) is its sensitivity t o bases but complete stability towards acids, even towards hot concentrated sulfuric acid. Trirnethylamine, triethylamine, and pyrrolidine have no effect, even when hot, if
water is excluded, but ring opening occurs slowly in the
presence of aqueous amines and instantaneously in the
presence of dilute alkali hydroxide solutions. Reaction with
potassium hydroxide solution yields potassium mesylmethanesulfonate ( 4 ) , identical with authentic material prepared
from trimethylammonium mesylmethanesulfonate 121 and
potassium hydroxide solution.
Received: November 6, 1968
[Z 901 IE]
German version: Angew. Chem. 81, 36 (1969)
By G. Opitz and H. R . M o h l f * ]
The sulfene dimer (I), which has been looked for in vain in
previous formations of sulfene (HzC=S02) from methanesulfonyl chloride and triethylamine and from diazomethane
and SO2, has now been obtained as follows: Methanesulfonyl
chloride and an excess of trimethylamine in tetrahydrofuran
at -20°C give a powdery addition product of unknown
structure[ll. When this suspension is slowly warmed to room
temperature, HC1 is eliminated and an ocher-brown color
develops (75 % of the sulfene thus formed can be detected by
If,
cycloaddition t o 1-(2-methyI-l-propenyl)pyrrolidine[~~).
after 90 h , the tetrahydrofuran is distilled off and the residue
is stirred with dilute hydrochloric acid, disulfene (1,3-dithietane 1,1,3,3-tetraoxide) ( I ) remains undissolved (yield 18 %,).
D
Disulfene ( I ) is slightly soluble in most solvents but can be
recrystallized from dimethylforrnamide (DMF) or aqueous
dimethyl sulfoxide (DMSO). It decomposes with formation
of a brown color above 28OoC. The calculated molecular
weight is obtained by mass spectrometry and osmometry.
[*I Prof. Dr. G . Opitz and Dipl.-Chem. H. R. Mohl
Chemisches Institut der Universitat
74 Tubingen, Wilhelmstrasse 33 (Germany)
[**I TMS as internal standard.
[I] G. O p i f z and K . Fischer, 2. Naturforsch. I8b, 775 (1963).
[Z] G. Opitz and D. Biiclrer., Tetrahedron Letters 1966, 5263.
A New Synthesis of Aminoquinazolines
By M . F. G . Stevens and A . Krerrrzhergerr*]
The class of arninoquinazolines contains members with antimalarial "1, antiviral [21, and analgesic activity 131. We have
now prepared aminoquinazolines by a general method in
which the quinazoline ring is ciosed before the amino group
is introduced, and which proceeds by a one-stage additive
cyclization.
It was known that (0-cyanopheny1)triazenes141 cyclize readily
and that various ring closures can be effected generally
by s-triazines ( I ) [51. It was thus to be expected that nitriles
(2) of anthranilic acids would, in reaction with ( I ) . initially afford N2-(o-cyanopheny1)formamidines (3) 161 which
are the C H analogs of (0-cyanopheny1)triazenes. The products
(3) are then stabilized by conversion into 4-aminoquinazolines ( 4 ) .
This ring closure o n reaction with (1) is the more remarkable
because (2a) is not cyclized by the triethyl orthoformate
method (although boiling it with formic acid yields 4h ydroxyquinazoline).
N
The N M R spectra (60 MHz) show four protons as a singlet
at T = 3.62 (in DMF), 3.58 (in DMSO), 3.43 (in hexamethylphosphorotriamide), 3.13 (in pyridine) [**I. Shaking the
solution with D2O causes this signal to disappear. Addition
o f triethylarnine to solutions of ( I ) leads t o strong signal
broadening, which can be reversed by a n excess of trifluoroacetic acid. When triethylamine and water are both added,
the H 2 0 and CH2 signals of ( I ) coalesce t o a common signal
which is shifted t o higher field on increase in the water
content. Similar exchange phenomena have been observed
for the somewhat less CH-acidic compound ( C ~ H ~ S O ~ ) ~ C H Z
and are ascribed to CH-acidity.
(4)
(3)
The I R spectrum o f ( I ) in KBr has bands at 2830-2990
(CH), 1340 (SO2 asym.), 1200 and 1090 (coupled vibrations),
860 (CS), and 680 cm-1, indicating a symmetrical compound.
The disturbance in the region of SO2 stretching vibrations is
removed on replacement of the H atoms.
64
Sublimation
266--268
The 1R spectrum of the tetradeuterio derivative (2),obtained
Recrystn. from HzO
275-277
by heating ( I ) with DzO in [D6]-DMSO, in KBr contains
Recrystn. from C Z H ~ O H 338-340
bands a t 2150-2270 (CD), 1350 (SO2 asym.), 1150 (SO2
sym.), 1020, and 825 cm-1. If the solution of ( I ) in D M F and
4-Amino-6-tnethyiquinazoline (46)
a little pyridine is treated at room temperature with bromine
until a permanent yellow color results, storage of the resulting
2-Amino-5-methylbenzonitrile(26) (2.6 g, 0.02 mole) and
mixture for 30 min and then pouring it into water affords the
s-triazine ( I ) (0.8 g, 0.01 mole) in anhydrous ethanol (10 ml)
crystalline tetrabromo compound (31, which can be recrystalare boiled together for 8 h. The solid material is filtered off
1
Angew. Chem. internat. Edit. 1 Vol. 8 (1969) j No. I
73
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