close

Вход

Забыли?

вход по аккаунту

?

Cyclopropenylidene.

код для вставкиСкачать
Cyclopropenylidene"*
By Hans Peter Reisenauer, Gunther Maier*,
Achim Riemann, and Reinhard W . Hoffmann*
Cyclopropenylidene 2a ++ 2b is of considerable theoretical interest"]. Until now, only the diphenyl[*]and bis(dia1kylamino) derivatives[31had been detected indirectly in
trapping reactions. We report here the generation of cyclopropenylidene 2 by flash thermolysis and its matrix isolation.
1
2a
4
2b
3
Received: April 25, 1984 [ Z 807 IE]
German version: Angew. Chem. 96 (1984) 596
ti
5
The quadricyclane derivative 114]was heated to 523 K
under conditions of preparative vacuum flash pyrolysis at
1 torr. The products, which were trapped at 77 K, underwent exothermic polymerization upon thawing; in addition, benzene 3 was isolated in almost quantitative yield. If
water was not completely excluded from the reaction, cyclopropenol 4 and dicyclopropenyl ether 5 were formed['].
This indicates that in the pyrolysis of 1 a C,H2-fragment
having an intact cyclopropene ring is cleaved off.
If the product of the pyrolysis is condensed with a large
excess of argonL6]onto a window at 10 K immediately after
it leaves the hot zone, the IR spectrum shows, apart from
the bands from benzene, four additional absorptions (Table 1). Within the normal variations of calculations of this
type (the calculated frequencies are ca. 10% too high), the
frequencies and relative intensities are consistent with
those of the four most intense IR bands predicted for 2['"].
Four other bands are too weak to be observed under our
experimental conditions.
Table 1. Experimental and calculated [la] IR spectrum of cyclopropenylidene 2.
Band frequencies [cm- '1
Found
Calc.
-
1279
1063
-
888
789
3457
3418
1759
1419
1191
1071
998
983
854
Rel. intensities
Found
Calc.
-
1.0
0.16
-
0.33
0.34
0.006
0.012
0.004
1.000
0.321
inactive
0.031
0.309
0.395
[*I Prof. Dr. G . Maier, Dr. H. P. Reisenauer
lnstitut fur Organische Chemie der Universitat
Heinrich-Buff-Ring 58, D-6300 Giessen (FRG)
Prof. Dr. R. W. Hoffmann, Dr. A. Riemann
Fachbereich Chemie der Universitat
Hans-Meerwein-Strasse, D-3550 Marburg (FRG)
[**I Small Rings, Part 51. This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen 1ndustrie.-Part
50: G. Maier, K. Euler, H. Irngartinger, M. Nixdorf, Chem. Ber., in
press.
Angew. Chem. Int. Ed. Engl. 23 (1984) No. 8
The presence of cyclopropenylidene 2 is confirmed by
the following experiment: Upon irradiation (A> 360 nm)
of the matrix-isolated pyrolysis product of 1, only the four
IR bands belonging to 2 disappear. Simultaneously, new
absorptions at 3390,3366,412,405,261, and 248 cm-' appear, whose frequencies correspond to the known values
for matrix-isolated propynylidene 6"l.
The photolytic conversion of 2 into 6 can also be observed using ESR spectroscopy. In accord with the singlet
ground-state of 2"], the ESR spectrum of the matrix-isolated product of pyrolysis exhibits no triplet signal. After
irradiation, the known spectrum[" of the triplet carbene 6
is obtained, consistent with the results of IR studies.
2 does not react when the matrix is tempered for several
hours at 35-40 K. After evaporation of the argon, a
brown, polymeric residue remains. Evidence for the formation of the interesting dimer of 2, 1,l-bicyclopropenylidene, could not be obtained.
Summary: Cyclopropenylidene 2 is stable in an argon
matrix at 10 K and has, as predicted"], a singlet groundstate.
[I] a) T. J. Lee, A. Bunge, H. F. Schaefer 111, J . A m . Chem. Soc., in press.
Prof. Schaefer is thanked for calculating the IR spectrum of 2 and for a
preprint; b) R. Gleiter, R. Hoffmann, J. Am. Chem. Soc. 90 (1968) 5457;
c) W. J. Hehre, J . A. Pople, W. A. Lathan, L. Radom, E. Wasserman, Z. R.
Wasserman, ibid. 98 (1976) 4378; d) N. C. Baird, K. F. Taylor, ibid. 100
(1978) 1333; e) H. Kollmar, ibid. 100 (1978) 2660; 0 R. Shepard, A. Banerjee, J. Simons, ibid. 101 (1979) 6174; g) W. W. Schoeller, Tetrahedron
Left. 21 (1980) 1509; h) P. Saxe, t i . F. Schaefer 111, J. Am. Chem. Soc. 102
(1980) 3239.
[2] W. M. Jones, M. E. Stowe, E. E. Wells, E. W. Lester, J . A m . Chem. Sor. 90
(1968) 1849, and literature cited therein.
[3] Z. Yoshida, Pure Appl. Chem. 54 (1982) 1059, and literature cited therein.
[4] a) D. N. Butler, 1. Gupta, Can. J. Chem. 60 (1982) 415; h) A. Riemann, R.
W. Hoffmann, J. Spanget-Larsen, R. Gleiter, Chem. Ber., in press.
[S] 4 and 5 polymerize above 243 K, and, hence, only NMR data (203 K,
[D,]acetone) could be obtained. 4 : 'H-NMR: 6=7.91 (d, 2H, J = 1.5 Hz),
3.76 (t, 1 H, J = 1.5 Hz), 3.35 ( I H); '?C-NMR: S= 120.8 (d, J(C-H)=227
Hz), 43.9 (d, J(C-H)=200 Hz). 5 : 'H-NMR: 6=7.86 (d, 4H, J = 1.6 Hz),
3.89 (t, 2H, J=1.6 Hz); "C-NMR: 6= 128.6 (d, J(C-H)=224 Hz), 48.7
(d, J/C-H)=200 Hz).
[6] Pyrolysis oven (G. Maier, G. Mihm, H . P. Reisenauer, Chem. Ber. 115
(1982) 801) flanged directly onto the vacuum shroud of the cryostat (Displex Closed Cycle Refrigerations System CSA 202, Air Products). 1 was
cooled to 223 K in a flask attached directly to the pyrolysis tube
lo-' torr), pyrolyzed at 820-Y20 K within 5 h, and condensed with a
large excess of argon onto the C'sl window (10 K, distance from end to
the hot zone ca. 5 cm).
[7] C. F. Kang, dissertation, Michigan State University 1972.
[S] R. A. Bernheim, R. J. Kempf, J. U.Gramas, P. S. Skell, J . Chem. Phys. 43
(1965) 196.
~
Direct Photochemical Cleavage of the Cyclobutane
Ring in Bicyclo[4.2.0loctane on 185nm Irradiation
in Solution**
By Waldemar Adam* and Thomas Oppenlander
By analogy to cyclopropanes, which recently have been
shown to exhibit interesting and diversified photochemistry on 185 nm irradiation in solution"], cyclobutanes are
[*] Prof. Dr. W. Adam, Dipl.-Chem. T. Oppenlander ['I
Institut fur Organische Chemie der Universitat
Am Hubland, D-8700 Wurzburg (FRG)
[']
Doctoral fellow of the Fonds der Chemischen Industrie.
[**I This work was supported by the Fonds der Chemischen Industrie and
the Deutsche Forschungsgemeinschaft.
0 Verlag Chemie GmbH, 0-6940 Weinheim, 1984
0570-0833/84/0R08-064I $ 02.50/0
641
Документ
Категория
Без категории
Просмотров
0
Размер файла
130 Кб
Теги
cyclopropenylidene
1/--страниц
Пожаловаться на содержимое документа