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Capture of Ketenes by Cyclo-Addition to Enamines.

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The o-(phenoxymethy1)- and o-(pheny1mercaptomethyl)benzoic acids are obtained by the reaction of w-bromo-o-toluyl
bromide [2] with the sodium salt of the corresponding phenols
and thiophenols and subsequent saponification.
The dibenzo[b,e]oxepinones and dibenzo[b,e]thiepinones do
not react with ketone reagents. With Grignard compounds,
however, such as ClMg(CH2)3N(CH3)2, they form, in very
good yields, the corresponding carbinols. These split off water
relatively easily. The basic propylidene compounds obtained
can be hydrogenated in the customary manner.
Received November 17, 1961 [Z 172/11 IE]
[l] T. Mukaiyama and T. Hata, Bull. chem. SOC.Jap. 34, 9 9
(1961).
[2] W. Davies and W . H.Perkin Jr., J. chem. SOC.(London) 121,
2203 (1922).
Capture of Ketenes by Cyclo-Addition to
Enamines
By Dr. G. Opitz, cand. chem. M. Kleemann,
and cand. chem. F. Zimmermann
The synthesis [l-31 of 3-dialkylaminocyclobutanonederivatives by cyclo-addition of ketenes to enamines is also possible
with ketenes produced in situ. A particularly simple route
requires only the dropwise addition of an ether solution of
an acid chloride (R2CH-COCI) to a mixture of enamins
and triethylamine. After the triethylamine hydrochloride is
removed, the solution contains the cyclobutanone base. In
this manner, ketenes may be captured which are accessible
only with difficulty, or not at all, in monomeric form, e.g.
methylketene, isopropylketene, butylketene, phenylketene,
phenoxyketene, acetoxyketene, chloroketene.
Suitable bases are t-enamines from mono- and di-substituted acetaldehydes. The enolizable cyclobutanone bases
suffer ring cleavage on heating and form vinylogous carboxylic
acid amides, while the non-enolizable ring bases are thermally
stable.
R2
0
-
Acid chloride
Yield
Enamine: I-Morpholino-isobutene
Propionyl
chloride
Chloroacetyl
chloride
Phenoxyacetyl
chloride
Acetoxyacetyl
chloride
Phen ylacetyl
chloride
Isobutyryl
chloride
Diethylacetyl
chloride
Diphenylacetyl
chloride
2,2,4-Mmethyl-3-morpholino 38-39
2,2-Dimethyl-3-morpholinoI-chloro2,2-Dimethyl-3-morpholino4-phenoxy2,2-Dimethyl-3-morpholino4-acetoxy2,2-Dimet hyt-3-morphofino4-phenyl2,2,4,4-Tetramethyl-3morpholino2,2-Dimethyl-3-morpholino4.4-diethyl2,2-Dimethyl-3-morpholino4,4-diphenyl-
80-8 I
112-113
95-96
b. p.
83-85/0.4 mm. Hg
39-40
Phenoxyacetyl
chloride
Isovaleryl
chloride
Caproic acid
ch 1ori de
Stearic acid
chloride
2,2-Dimethyl-3-piperidino4-phenoxy2,2-Dimethyl-3-piperidino4-isopropyl2,2-Dimethyl-3-piperidino4-hutyl2,2-Dimethyl- 3-piperidino4-hexadecyl-
Enamine: I-Pyrrolidino-isobutene
Propionyl
chloride
Ethyl-butylacetyl chloride
1
2,2.4-Trimethyl-3-pyrrolidino.
2,2-Dimethyl- 3-pyrrolidino4-ethyl-4-butyl-
b. p.
Received November 24,1961
30
I2 176/13 IE]
[l] G. Opitz, H . Adolph, M. Kleemann, and F. Zimmermann,
Angew. Chem. 73, 6 5 4 (1961).
[2] R . H . Hasek and J. C. Martin, J. org. Chemistry, in the press.
[ 3 ] G. A. Berchrold, private communication by [2].
R2
I
R1-CH-CO
RI-C-CO
)N1!LR'
+
\
,N-CH=L-R3
'N-CH
I l l
CHZ-R~
/
Rz = H or alkyl
Introduction of the Bromomethylene Group using
the Wittig Reaction
R2 = H
When I-piperidinopropene is reacted with ketene or acetyl
chloride/triethylamine, 2-methyl-3-piperidinocyclobutanone
is formed, which, on standing changes to a mixture of 1piperidino-I-pentene-3-oneand 1-piperidino-2-methyl-butenone. Analogous behavior is shown by 2,4-dimethyl-3piperidinocyclobutanone formed with propionyl chloride/
triethylamine, by 2-ethyl-3-piperidinocyccyclobutanoneformed
from 1-piperidinobutene and ketene or acetyl chlorideltriethylamine, and by 2-ethyl-3-piperidino-4-methyl-cyclobutanone from 1 -piperidinobutene and propionyl chloride/triethylamine. Other cyclobutanone bases are summarized in
Table 1.
The ring bases have a sharp carbonyl band at 1766-1781 cm-1
in the IR-spectrum. In the reaction of l-morpholinocyclohexene (I) with ketene, the formation of the bicyclic cyclobutanone base I1 can be detected by IR-spectroscopy. The
main product is I-morpholino-2-acetylcyclohexene (III),
which is also formed in the ring cleavage of 11.
By Dr. G. Kobrich
Organisch-Chemisches Institut der Universitat Heidelberg
(Germany)
Triphenylphosphine reacts with methylene bromide to form
a mixture of I and I1 [l]. Pure I1 (m.p. 241-242.5"C.) is
obtained in 74 % yield from triphenylhydroxymethylphosphonium bromide and phosphorous pentabromide.
0
(I
I'
I1
'O/
Angew. Chem. internat. Edit. / Vol. I (1962) No. 1
I11
@
(CsHshP-CH?-P(GHsh
I
2Bre
0
(GH.+P-CHzBr
I1
BrQ
If the chloromethylenation of compound I1 is attempted
by the method of G. Wittig and M . Schlosser [2], the vinyl
compound 111 (yield 40 %; Amax = 233 mp; log E = 3.76) is
111
I
M. p.
Cyclobutanone
Enamine: I-Piperidino-isobutene
Chemisches Institut der Universitat Tubingen (Germany)
R I 1 - y
Table 1. Synthesis of Cyclobutanone Bases from Enamines and Acid
Chlorides in the Presence of Triethylamine
1v
V
formed from n-butyllithium in ether and with @-cyclocitral,
rather than the expected product IV; with phenyllithium as
base, on the other hand, a mixture of 111 and IV is formed
in the ratio 3 :2 (determined by gas chromatography), besides
bromobenzene. The bromo compound IV (Amax = 238.5 mp;
log E = 3.80), which readily polymerizes, may be converted to
51
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