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Aziridine Imines.

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As shown in the Table, hydrolysis of the reaction mixtures
usually gives the expected cycloadditionproducts. The2,3,4,5tetraphenylpyrrole produced is, however, a dehydrogenated
cycloaddition product. The products isolated appear homogeneous o n thin-layer chromatography and N M R spectroscopy, and their structures follow from analyses, molecularweight determinations, N M R and mass spectra, and from
the mode of preparation.
In these reactions the unsaturated hydrocarbon presumably
forms a x-bond to the lithium ion. The question whether the
subsequent 3 + 2 cycloaddition (Huisgen's nomenclature 151)
occurs in one stage or in two stages [by way of an intermediate
of type (S)] is under present study.
valence isomerization of heteromethylenecyclopropanes 131
we report here o n a stereoselective synthesis of such compounds.
By treating the a-bromoamidines ( I ) and ( 2 ) (which can be
prepared in the usual way from the corresponding N-methylamide) with potassium rert-butoxide in ether we were able
t o obtain compounds in 7&80% yield which, according to
elemental analyses, molecular weight determinations (osmometric in benzene), mass spectra, and I R spectra [extremely
high C=N frequency (see Table 2) and absence of N H bands],
have a n aziridine imine structure.
At low temperatures the 1 , 3 elimination of a-bromoamidines
proceeds with both high regio- and high stereo-selectivity; at
--40 "C, compound (2) yields predominantly (4) [(4) : ( 5 ) 86 : 141, while at room temperature a mixture of about equal
amounts of (4) and (5) is obtained. 1R and N M R spectra
permit unequivocal assignment of structure (see Table 2).
As expected, the electronegativity of the atoms participating
in the multiple bonding plays a significant part in the course
of addition of 2-azaallyllithium compounds. Thus reaction
of (3) with carbonyl double bonds leads t o open-chain compounds of type (7) and not t o oxazole derivatives of type ( 6 ) .
(3), b.p. <15 oC/O.OOl torr
IS'), m.p. -3 to --2.5 ~C
( 4 ) , m.p. 19-20 "C (pentane)
Received: March 31, 1970
[ Z 192 IE]
German version: Angew. Chem. 82, 396 (1970)
[*] Prof. Dr. Th. Kauffmann, H. Berg, and
Dipl.-Chem. E. Koppelmann
Organisch-Chemisches Institut der Universitzt
44 Munster, OrlCansring 23) Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.
[I] Organo-lithium and -aluminum Compounds, Part 3. Part 2 : 121.
121 Th. Kauffmann, E . Koppelmann, and H . Berg, Angew. Chem.
82, 138 (1970); Angew. Chem. internat. Edit. 10, 163 (1970).
[3] R. B. Woodward and R. Hoffmann, Angew. Chem. 81, 797
(1969); Angew. Chem. internat. Edit. 8, 781 (1969).
[4] 1,3-Dipolar cycloadditions are, it is true, related to anionic
,2]-cycloaddition [3] but differ therefrom in non-participation of the anions.
[ S ] R . Huisgen, Angew. Chem. 80, 329 (1968); Angew. Chem.
Internat. Edit. 7, 737 (1968).
At -4OoC, both ( I ) and (2) yield almost exclusively the
transisomers (stereoselectivity > 90%). which arein equilibrium with their thermodynamically more stable cis isomers at
room temperature.
In order t o distinguish between inversion of the ring nitrogen 141 and syn-anti isomerization of the imino group, the rate
of this isomerization was followed by N M R spectroscopy.
The data given in Table 1 are only consistent with a slow
syn-anti isomerization of the imino group.
Table 1.
Equilibrium and rate constants of the syn-anti isomerization
of ( 3 ) and ( 4 ) at 36 j. I ' C .
Aziridine Imines [**I
By Helmut Quast and Edeltruud Schmitt [*I
Although aziridones (a-lactams) [I1 have already been known
f o r some years, attempts t o prepare aziridine imines have so
far failedr21. In connection with our investigations on the
Angew. Chem. internat. Edit. 1 Vol. 9 (1970)
No. 5
The configuration of trans-(3) and trans-(4) is proved by the
observed coupling of the H o n C-3 with the methyl group on
the imino nitrogenrsl; cis-(3), (41, and cis-(5) show only
singlets. The N M R spectra in benzene support the assignment of configuration: a s expected, the upfield shift of the
signals for all cis protons was larger than for those trans to
the alkyl groups o n the imino nitrogen 151.
38 1
The kinetically preferred formation of trans-aziridine imines in
the intramolecular SN reaction via a semi W-like transition
state[6J can be explained by the greater stability of the configuration ( 6 ) of the intermediate amidine anion, in which
mutual repulsion of the lone pairs is at its lowest [TI.
Table 2.
IR and N M R data of the aziridine imines.
meric thermolysis products).
Received: March 25, 1970
[ Z 188 IE]
German version: Angew. Chem. 82, 395 (1970)
J = 0.6 Hz)
1.92 [a1
1 .oo
J = 0.7 Hz
J = 0.7 Hz)
H. Quast and E. Schmitt
Institut fur Organische Chemie der Universitat
87 Wurzburg, Landwehr (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft
[ l ] I . Lengyel and J . C . Sheehan, Angew. Chem. 80, 27 (1968);
Angew. Chem. internat. Edit. 7, 25 (1968).
[2] J . A . Deyrup, M . M . Vestling, W . V . Hagan, and H . Y. Yun,
Tetrahedron 25, 1467 (1969); K . Ichimura and M. Ohta, Tetrahedron Letters 1966, 807; D . Se-vferth and R . Damrauer, ibid.
1966, 189.
131 H. Quasi and E . Schmitt, Angew. Chem. 81,428,429 (1969);
Angew. Chem. internat. Edit. 8, 448, 449 (1969); Chem. Ber.
[*] Dr.
f runs- (4)
We have not yet been able to detect a valence isomerization
(4)+ ( 5 ) either directly or indirectly (by identification of iso-
[a] Broad signal.
[bl Measured in the absence of solvent.
Compound (4) starts to decompose at 5OoC [+(7) + (81,
halflife about 17 h at 6OoC]; ( S ) , o n the other hand, only
decomposes above 120 OC [ 4 9 ) ( l o ) ]to afford isocyanide
and imine in quantitative yield (cf. 11-31). This decomposition
serves as independent proof of the structure of ( 4 ) and ( 5 )
and permits a simple preparation of pure (5) by fractional
thermolysis of a mixture of ( 4 ) and ( 5 ) at 100 "C.
103, 1234 (1970).
[41 H . Kessler, Angew. Chem. 82, 237 (1970); Angew. Chem.
internat. Edit. 9, 219 (1970); M . Jautelat and J . D . Roberts,
J. Amer. chem. SOC.91, 642 (1969).
[ 5 ] G. J . Karabatsos and S . S . Lande, Tetrahedron 24, 3907
(1968); G. J . Karabatsos and R . A . Taller, ibid. 24, 3923 (1968).
161 A. Nickon and N . H . Werstiuk, J. Amer. chem. SOC.89,
3914 (1967).
171 N . L. Owen and N . Sheppard, Proc. chern. SOC.(London)
1963, 264.
Problems of Modern Silicone Chemistry
By Walter NoN[*J
The diversity of this subject, particularly as regards industrial
aspects, is illustrated by three selected topics.
1. Synthesis of silanes
Little use has been made of the many recommendations based
o n laboratory work in the technical development of the direct
synthesis of methylchlorosilanes (use of 3-phase Cu&; other
metallic catalysts in place of, or in addition to, copper; pretreatment of the silicon; etc.). The process has reached a high
level of development owing to process-engineering measures
and particularly to the use of fluidized beds. Apart from the
usual addition reactions of the Si-H bond, substitution reactions of bromomethylsilanes (or siloxanes) have proved useful for the production of organo-functional silanes. Bromo(sometimes also chloro-)methylsilanes have assumed a key
role in the preparation of amino-, hydroxy-, mercapto-, or
carboxy-substituted derivatives; they also permit ring-closure
reactions (silamorpholine).
2. Chain polymers
Recent publications have paid detailed attention to mechanisms of "self crosslinking" of silicone rubber. Chain polymeric polydimethylsiloxanes having terminal OH groups are
made into pasteswith crosslinkingagents of the typeCHsSiX3,
fillers, and other additives; these pastes may be stored un-
changed in the absence of moisture. When exposed to the air,
they react with the water vapor present to give crosslinked
soft-elastic materials. Crosslinking agents having X = carboxy, amino, N-alkylacylamide, o r ketoxime are of industrial
interest. The products are used as sealants in the building industry.
The properties of polydimethylsiloxanes are modified considerably by anionic copolymerization with diphenylsiloxanes to give regular polymers of high crystallinity. Introduction of amino or hydroxymethyl groups or co-condensation with polyethers increases the hydrophilic character of
the molecules; in both cases interesting surface activity results from the increase in polarity of the molecules.
3. Surface chemistry
This generally plays a n important role in the uses of silicones.
Force/area isotherms of monomolecular siloxane films, which
were registered on a continuously operating, automatically
recording film balance, show variations depending upon the
nature of the substituents. The molecules of those siloxanes
that are of industrial interest because of their surface activity
lose their coil or helical form and are converted into "spreading chains" that are bonded to the water via their Si-0-Si
bonds andcan beconvertedinto a two-dimensional closepacking on compression (e.g. dimethyl-, methyl-&, methyl-y-trifluoropropylsiloxanes). Under such conditions, dimethylsiloxanes form surface layers in which only hydrocarbon
groups are directed toward the gas phase. An increase in the
size of the aliphatic groups, introduction of diphenylsiloxane
Angew. Chem. internat. Edit. I Vol. 9 (1970)
1 No.
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imine, aziridine
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