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Dipole Metathesis.

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( 3 a ) furnishes the expected pentyl bromide (6a), compound
( 4 d ) affords either 1-bromo-2,2-diphenylethylene ( 6 b ) (m.p.
40 to 41 " C ; lit. value[4Jm.p. 41 to 42°C) or 1,l-dibromo-2,2diphenylethylene ( 6 c ) (m.p. 83 to 84°C; lit. value[51 m.p.
83 "C), depending on the amount of bromine used.
61025-06-7; ( S a ) , 38563-47-2; ( 5 h), 61025-07-8: (60). 110-53-2; ( 6 6 ) , 1324958-6; (6c), 2592-73-6; (7u/, 3095-87-2; (76),2215-16-9: Br(CH2j3CH3,10965-9; BrCH2CH=CH2, 106-95-6; BrCH2Ph, 100-39-0: CH3(CH2)2COH.12372-8: C6H5COH,100-52-7; (CH2)&0, 108-94-1; PhCOPh. 119-61-9
-~
[I]
[2]
i3aJ
19%
( C,H,)2As( C H Z ) ~ - C H,
I Bq
[3]
B r (CH2)4-CH3 ( 6 a ) 7 9%
+
20-90 "C
(5uJ
B rAs(C 6H5)2
PH
(C 6H5)
2As-C H2-C (C6H5)
I Br*
20-12OY
(7U)
92.570
[4]
[5]
G. 0.Doak and L. D. Freedman: Organometallic Compounds of Arsenic,
Antimony and Bismuth, Wiley, New York 1970.
Halodemetalations are also known for stibanes, bismuthanes, germanes.
stannanes, and plumbanes. We are investigating whether these reactions
are also suitable for the introduction of halogen atoms and halogenated
hydrocarbon units into organic compounds.
Prepared according to G. J . Burrovvs and E. E. Turuer, J. Chem. Soc.
117, 1381 (1920); 119. 428 (1921): A . Merijunian and R . A . Zingaro,
Inorg. Chem. 5 , 187 (1966).
P. Lipp, Ber. Dtsch. Chem. Ges. 56, 569 (1923).
K . Ziegler, Justus Liebigs Ann. Chem. 434, 61 (1923).
B r-HC =C (C6H5)2 /6bJ 7 5%
+
Dipole Metathesis[**]
Thus compound (2) can be utilized for stepwise chain
elongation of alkyl halides by one C atom at a time. The
available experimental data are not yet sufficient to provide
a basis for general statements about the synthetic operations
possible on carbonyl compounds with the aid of (2).
The structures of the newly prepared compounds follow
from the results of elemental analysis and from their spectroscopic data (MS, IR, 'H-NMR).
Procedure for the chain elongation of n-butyl bromide
(All reactions performed in a nitrogen atmosphere and in
anhydrous N2-saturated solvents.)
a) n-Pentyl(dipheny1)arsane oxide: A freshly prepared solution of lithium diisopropylamide (1 7.6 mmol) in T H F (40ml)
is added dropwise at -40°C to a stirred solution of methyl(dipheny1)arsane oxide (4.16 g, 16.0 m m ~ l ) [ in
~ ] T H F (250ml).
Methyl(dipheny1)arsane oxide precipitated at -40°C dissolves
during the reaction. After 30 minutes' stirring, n-butyl bromide
(2.19g, 16.0 mmol) in T H F (10mI) is added dropwise to the
resulting clear yellow solution and the mixture warmed to
65°C for 1 h. Water and chloroform are added to the almost
colorless solution, the phases are separated, the aqueous phase
extracted with chloroform, and the dried chloroform phases
are evaporated down. The crystalline residue is worked up
by column chromatography [silica gel, chloroform/ethanol
(85 : 1S)]: 3.6 g (72 %) of (3 a ) and 0.90 g (21 %) of methyl(dipheny1)arsane oxide are obtained.
b) ti-Pentyl(dipheny1)arsane: After reduction of (3 a ) with
LiAlH4 (1 90 mg, 5.0 mmol) in T H F (55 ml) at room temperature, work-up [by analogy with a), but without chromatography] affords 2.94g (98 %) of the oily arsane which is homogeneous on chromatography.
c) ti-Pentyl bromide: A solution of Br2 (1.12g, 7mmol)
in CCI4 (5ml) is added dropwise at room temperature to
a solution of the arsane (2.10g, 7mmol) in CC14 (15ml). A
yellow solution is formed above a brownish red oil. The
solvent is drawn off in vacuo, and the residue heated to 90°C
for 2 h. The resulting n-pentyl bromide (79 % according to
gas chromatography) can be separated from chloro(diphenyl)arsane (92.5%) by distillation.
Received: October 16, 1976;
revised: October 28, 1976 [ Z 595 IE]
German version: Angew. Chem. 89, 52 (1977)
CAS Registry numbers:
(I), 61024-98-4; ( 2 1 , 61024-99-5: ( 3 a ) , 61024-00-1; ( 3 b ) . 61025-01-2: (3c),
61025-02-3: ( 4 a ) . 61025-03-4; ( 4 h ) , 61025-04-5; ( 4 1 ) , 61025-05-6: ( 4 d ) ,
54
By Klaus Burger, Helmut Schickaneder, and Claus Z e t t l l l
1,5 Dipoles of type (I)['] are accessible by electrocyclic
ring opening from 1,5-diazabicycl0[3.3.0]oct-2-enes[~~.
The
azomethinimine system present in ( I ) reacts with double
bond systems by [3 +2] cycloaddition. The cycloadducts fulfil
the requirements necessary for a [3 +2] cycloreversion. The
initiation temperature depends upon the nature of the substituents at C-3 and C-4.
H3C CH3 R ' , R ~
F3C C F 3 H
"
F
R
CF3
2
"0%;
-
HF3C C F 3 H
Hv
1 ..R4
AT
R4 R3
+
H
F3C C F 3
(3)
F3C
CF3
f4)
,
1
R ' u R 3
RZnR4
Reaction of ( I ) with ethylenetetracarbonitrileproceeds via
(2) togive the stable 1,3 dipole (3 a ) and 4,4-bis(trifluoromethyl)buta-1,3-diene-l,l-dicarbonitrile( 4 a ) . Reaction of ( I ) with
fumaronitrile affords, apart from two stereoisomeric [3 23
cycloadducts [(2 b'), (2b")l and the cycloreversion products
" ( 3 b), ( 4 b)], a [3 21 cycloadduct ( 5 a ) derived from (3 b )
and fumaronitrile, which becomes the major product on use
of an excess of fumaronitrile and at higher temperature. The
reactions of ( I ) with dimethyl fumarate and maleate proceed
in a similar manner; however, in these cases only one cycloadduct of structure (2) could, as yet, be isolated along with
(5) in each case.
+
+
[*I
Priv.-Doz. Dr. K. Burger. Dr. H. Schickaneder, and Dip1:Chem. C.
Zettl
lnstitut f i r Organische Chemie der Technischen Universitat
Arcisstrasse 21, D-8000 Miinchen 2 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft
(Project Bu 277/4) and the Fonds der Chemischen Indnstrie.
Anyew. Chem. I n t . Ed. Enyl. 16 (1977) N o . I
Table I . Compounds ( 2 ) to ( 5 ) prepared. All compounds gave correct elemental analyses.
R'
R2
H
CN
H
H
CN
H
CN
H
CO2CH3
-
CN
H
H
H
COzCH3
H
H
H
[d]
R3
~
R4
CN
H
C02CH3
H
~
CN
CN
CN
COzCH3
H
M.p.
I"/.I
rc1
35
9
41
30
81
121
127- -129
76
oil
133- -135
30
17
20
131
92
105
2250 [a], 1675 [b]
2250 [a], 1680 [b]
1750-1 730,1675 [b]
176&1710, 1680 [c]
2215, 2195, 1468 [h]
2240,2220,1655,1610 [ c ]
2220, 1650, 1595 [c]
2255 [a, b]
1760 -1730 [b]
1758, 1742 [b]
Very weak. [b] In KBr. [c] As film.
The reaction sequence ( I ) --t ( 2 ) + ( 3 ) ,comprising a [3 + 21
cycloaddition and subsequent [3 +2] cycloreversion, is a
dipole metathesis. It provides a general entry to variously
substituted azomethinimines ( 3 ) and a new I ,3-butadiene
synthesis. The reaction ( 1 ) + ( 2 ) --t ( 3 ) + ( 5 ) is a new variant
of the dipolar cyclosynthesis.
General procedure
Compound ( I ) (4.10g, 10mmol) and a little more than
an equimolar amount of a dipolarophile are heated in tetrahydrofuran (50ml) under reflux for 2 to 5d. After the solvent
has been distilled off, any solids are removed and the remaining
oil is fractionated by column chromatography with chloroform
on silica gel.
Received: September 13, 1976 [Z 591 a IE]
German version: Angew. Chem. 8Y,60 (1977)
CAS Registry numbers:
( I ), 60935-02-6; ( 2 ) . 60949-91-9; ( Z h ) , 60935-03-7; ( Z r ) , 60935-04-8; ( 3 a ) ,
60935-05-9: ( 3 h ) , 60935-06-0; ( 4 n ) , 60935-07-1 ; ( 4 b ) , 60935-08-2; ( 5 b ) ,
60935-09-3: ( 5 c J, 60935-1 0-6: ethylenetetracarbonylnitrile,670-54-2; fumaronitrile, 764-42-1 : dimethyl fumarate, 624-49-7; dimethyl maleate, 624-48-6
~
IR [cm-'1
Yield
__
~
[I] 1.5 Dipoles are defined as 1,3 dipoles with internal octet stabilization
which are i n conjugation with a n unsaturated substituent ( H . Reidirzgrr,
Chem. Ber. 103. 1900 (1970)).
[2] K . Birryrr, H . Schickorieder. and C. Z e f f l ,Synthesis 1976, 803.
methyl propiolate the orientational isomers ( 2 a ) and ( 2 b )
are formed.
The cycloadducts ( 2 ) are able to undergo electrocyclic
ring opening. The position of the equilibrium ( 2 ) * ( 3 )
depends upon the nature of the substituents R' and R213'.
While ( 2 a ) coexists with the 1,7 dipolar species ( 3 a ) in
a 78:22 equilibrium at room temperature in CDC13, only
the 1,7 dipolar species ( 3 b ) can be detected by I9F-NMR
spectroscopy in the case of the orientational isomer ( 2 b ) .
The adduct of ( I ) with dimethyl acetylenedicarboxylate exists
entirely as ( 2 c ) under the same conditions.
Table I . Compounds (2) to ( 4 ) prepared. All compounds gave correct
elemental analyses.
R'
R'
Yield
["/.I
(2a)
(20
(3b)
(4a)
H
COXH3
C02CH3
H
C02CH3
C02CH3
H
C02CH3
49
73
15
70
M.p.
I"C1
IR [crn-']
107
107
oil
oil
1670 (bl), 1572 [;I]
1752. 1690(br).15XO[a]
1715, 1617 [b]
1720-1670,
1650, 1587
[bl
[a] In KBr. [b] As film,
A General Procedure for Generating Conjugated
1,x D i p o l e s [ * * ] 1'1
By Klaus Burger, Helmut Schickaneder, and Claus Zettlc']
1,5 Dipoles of structure ( I ) [ * ] add substances with triple
bonds to form 1,5-diazabicyclo[3.3.O]oct-2-enes ( 2 ) ; with
The 1,7 dipole (3 a ) likewise reacts with substances containing triple bonds as an azomethinimine; the major product
( 4 a ) can again undergo electrocyclic ring opening as a 1,5-diazabicyclo[3.3.0]oct-2-ene.
[*] Priv.-Doz. Dr. K. Burger, Dr. H. Schickaneder, and Dipl.-Chem. C.
Zettl
lnstitut fur Organische Chemie der Technischen Universitat
Arcisstrasse 21, D-8000 Miinchen 2 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft
(Project Bu 27714) and the Fonds der Chemischen Industrie.
Repetition of the reaction sequence of [3 + 23 cycloaddition
of an
and e~ectrocyclicring opening permits construction of 1,xdipoles from 1,3 dipoles. During each extension
step the dipole end shifts from one to the other nitrogen
atom. The reaction is also a new type of oligomerization
of acetylenes.
Amgew. Chem. I n ( . Ed. Engl. I 6 (lY77) N o . I
55
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