close

Вход

Забыли?

вход по аккаунту

?

Electrophilic Behavior of Tri-tert-butylcyclobutadiene.

код для вставкиСкачать
N a H C 0 3 solution, washed once more with citric acid solution
and water, dried over MgS04, and evaporated. The esters
( 5 0 ) can be used without further purification for peptide
synthesis. For analysis, the product can be crystallized, if
necessary, from ethyl acetate/light petroleum.-Variant
B:
The components are stirred in dioxane/water ( 2 :1) (150ml)
at 20°C for 1-2 days, the mixture evaporated down and
treated as for variant A.
Received: January 31, 1979 [Z 173 IE]
German version- Angew. Chem. 91. 326 (1979)
[I]
[2]
[3]
[4]
[5]
[6]
Activated Carboxylic Acid Derivatives, Part 4.-Part 3: H . Schmidt,
0. Hullirzer, A . Seewald, W Steglidi, Chem. Ber., in press.
0. Hollifzer, A . Seewald, W Stegiich, Angew. Chem. 88, 480 (1976);
Angew. Chem. Int. Ed. Engl. 15,444 (1976).
Cf. A . Ali, B. Weinsrein,J. Org. Chem. 36,3022(1971); A. Ali, F. Fahrenholz,
B. Weinstein, Angew. Chem. 84, 259 (1972): Angew. Chem. lnt. Ed.
Engl. 11, 289 (1972); U . Ragnarson, S. M . Karlsson, B. E. Sandberg,
Acta Chem. Scand. 26, 2550 (1972); W Steglich, S. Hinre. Synthesis
1976, 399.
Examples: M. Frankel, D. Ladkany, C. Gillon, Y Whmn, Tetrahedron
Lett. 1966, 4765; E Wolman, D. Ludkany, M. Frankel, J. Chem. SOC.
C 1967. 689: W Broadhent, J . S . Morley, 8. E. Stone, ihid. 1967, 2632.
F. Weygand, A . Prox, L. Schmidhnmmer, W Konig, Angew. Chem. 75,
282 (1963); Angew. Chem. Int. Ed. Engl. 2, 183 (1963).
C. Birr, W Lochinyer, G. Slahnke,P. Lung, Justus Liebigs Ann. Chem.
763, 162 (1972).
Electrophilic Behavior of
diene“]
Tri-revr-butylcyclobuta-
By Giintker Maier and Fritz Kohler[*l
Dedicated to Professor Horst Pommer on the occasion of his
60th birthday
The cyclobutadiene ( I ) , which is readily accessible from
2,3,4-tri-tert-butylcyclopentadienonevia the corresponding
“housenone”[2], is extremely versatile in its reactions. It
behaves both as a diene and as a dienophilel3”1,as a nucleophile
and as a base[3b1,and as a potential diradicalr3‘! No evidence
of electrophilic properties has yet been reported for ( I ) , but
our latest studies now close this gap. This chemical omnipotence of the cyclobutadiene 4rr-system confirms its exceptional
nature.
dianion (6) occurs. The H/D NMR coupling constant in
D1-(3) proves the trans c~nfigurationl~l.
A hydride ion is also added to (1 ) I 6 ] . Both the direct action
of lithium aluminum hydride on ( 1 ) and the circuitous route
oia the halogen adducts ( 4 ~ 1 ) ‘ ’I~ sor ( 4 b ) [‘H-NMR (CDC13):
6=1.18 (9H), 1.20 (9H), 1.36 (9H), 5.13 (1 H); I3C-NMR
(CDC13):6=28.24,30.04,31.10,33.62,34.31,40.48,
58.60, 85.53,
149.89, 155.791 lead to 1,2,3-tri-tert-butylcyclobutene
(5)141.
Nucleophilicity and basicity of ( I ) parallel the excellent
donor properties of unsubstituted cyclobutadiene and its alkyl
derivatives[81.It is therefore all the more surprising that ( 1 )
should also show pronounced electrophilic character. The
reason for this dualism is to be found in the pseudo-Jahn-Teller
effectigaJwhich gives rise to a low-lying LUMO and a highenergy HOMO, and thus endows ( I ) with the properties
of a nucleophile and of an electrophilefgbl.The addition of
tert-butyllithium-also known in the case of open-chain butadiene[’ol-is even able to overcome the kinetic hindrance
of three tert-butyl groups as a result of the energetic destabilization of the x-system.
Received: January 19, 1979 [Z 175 IE]
German version: Angew. Chem. 9 / . 327 (1979)
CAS Registry numbers:
( I ) , 51067-53-9; (2), 69631-78-3; ( 3 ) , 69631-79-4; ( 4 a ) , 69631-80-7; ( 4 h ) ,
69631-81-8; (5),37715-08-5
[I]
[2]
[3]
[4]
[5]
61
71
81
[9]
[lo]
Small Rings, Part 26. This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen 1ndustrie.-Part
25: C. M a i e r , S. Pfriem, U . Schafer, R. Mafusch, Angew. Chem. YO,
552 (1978): Angew. Chem. Int. Ed. Engl. 17, 520 (1978).
G. Maier, U . Schafer, W Sauer, H. Harran, R. Matuach, J . F . M .
O h , Tetrahedron Lett. 1978, 1837.
a) Review: C. Maier, Angew. Chem. 86, 491 (1974); Angew. Chem.
Int. Ed. Engl. 13,425 (1974): b) G. Maier, W Suuer, ibid. 87. 675 (1975)
and 14, 648 (1975): c) ibid. 89, 49 (1977) and 16, 51 (1977).
A . E. Feirirtg, J . Ciabattoni, J. Am. Chem. SOC. 95. 5266 (1973).
JHDis ca. 0.4 Hz for D,-(3). This gives JHH-2.5 Hz,which corresponds
more closely to the trans coupling (1.7 Hz) typical of allylic cyclobutene
protons than to cis coupling (4.9Hz). We are grateful to Dr. H . - 0 .
Knliizoicski for this configurational assignment.
This reaction is not very clear-cut; gas chromatography shows the
crude product t o contain about 18 % of (S).
Presumably, the halogen adducts are also tmns-configurated. In the
compound 3,4-dichlorotetramethylcyclobutene
f ~ r m e r l y ‘used
~ ’ as reference substance the chlorine atoms are also trans-oriented contrary
to the original assumption: R. Criegee. Angew. Chem. 80,585 (1968);
Angew. Chem. Int. Ed. Engl. 7 , 559 (1968).
G. Muier, H . P. Rcisennuer, Tetrahedron Lett. 1976, 3591: C. Maier,
W Mayer, C . Haucke, R. Askaiii, Angew. Chem. 85, 1057 (1 973); Angew.
Chem. Int. Ed. Engl. 12, 1016 (1973).
a) L. Salem: The Molecular Orbital Theory of Conjugated Systems.
Benjamin, Reading 1966, pp, 4 8 6 8 ; b) I . Fleming: Frontier Orbitals
and Organic Chemical Reactions. Wiley, New York 1976.
W H . Glaze, D. J . Berry, D. R. Duncan, J. Organomet. Chem. 52,
233 (1973).
Ester and Lactone Formation with the Reagent 1 , s
Dihydro-4,6-dimethyl-2-thioxo-3-pyridinecarbonitrile
(4n). x
=
c1
(5)
16)
(46), X = Br
Reaction of ( I ) with tert-butyllithium in diethyl ether in
the presence of N,N,N’,N’-tetramethylethylenediamineat
-78°C smoothly affords the adduct (2). Aqueous work-up
gives a high yield (94 % based on the cyclopentadienone reactant) of 1,2,3,4-tetra-tert-butylcyclobutene
(3)[41. Treatment
with D2O gives only the monodeuterated derivative D,-(3).
This means that addition does not proceed beyond the
monoanion (2) ; no deprotonation to give the “aromatic”
[*] Prof. Dr. G. Maier, F. Kohler
lnstitut fur Organische Chemie der Universitat
Heinrich-Buff-Ring 58, D-6300 Lahn-Giessen 1 (Germany)
308
By Ulrich Schmidt and Dieter Heermann[*l
Dedicated to Professor Horst Pommer on the occasion of his
60th birthday
Several synthetic routes affording entry to macrolactones
have been described in recent years[‘-4! So far, however,
no single method has proven universally satisfactory for the
synthesis of complex macrolides.
We report here on the formation of esters with the readily
accessible reagent 1,2-dihydro-4,6-dimethyl-2-thioxo-3-pyri[*] Prof. Dr. U. Schmidt, Dr. D. Heermann
Institut fur Organische Chemie, Biochemie und Isotopenforschung der
Universitat
Pfaffenwaldring 55, D-7000 Stuttgart 80 (Germany)
Angew. Chem Int. Ed. Engl. 18 ( 1 9 7 9 ) N o . 4
0 firlag Chemie, GmbH, 6940 Weinheim, 1979
0570-0833179/0404-03O8 $ 02.5010
Документ
Категория
Без категории
Просмотров
1
Размер файла
144 Кб
Теги
butylcyclobutadieneч, behavior, electrophilic, tri, tert
1/--страниц
Пожаловаться на содержимое документа