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Nickel(0)-Induced Synthesis of Ethyllithium from Lithium Hydrogen and Ethylene.

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Cheni. 88. S2 (1976): Angew Cheni. Int. Ed. t n g l . / 5 , 48 (1576); H. BonneK H . Tsa).. ibid 88. 50 (1976) and I S . 46 { 1976). respective-
mom. C Kriger,
ly.
C61
[6j We thank Dr. R Mvnotr for recording and interpreting the "C-NMR spectrum (25.2 MHz. shifts referred to TMS. multiplicities determined by off-resonance or gated-decoupling).
Nickel(0)-Induced Synthesis of Ethyllithium from
Lithium, Hydrogen, and Ethylene
By Klaus Jonas and Klvus Richard
Nil
- Ni2
2 618
c7
Fig. I Structure of the complex Ni(C,,H,,NiLi),(THF)4 (3) Bond lengths in
A.
ringI4I.A hetero-metal multicenter bond''] is observed for the
live-coordinated carbon atom (Cl) of the twelve-membered
ring which is bonded to Ni2 through three ?r-bonds. This
leads to an acute angle of 78" for Ni C1- Li which is typical for electron deficient bonds and is accompanied by considerable distortion of the v-bonded interaction Ni2Cl C2
(Fig. 2).
c 11
(COD),Ni t 2 Li
/
P~rschkd"]
In general high reaction temperatures are necessary for the
synthesis of alkali-metal hydrides from the elements['', although sodium hydride can be formed at room temperature
and normal pressure in tetrahydrofuran if both naphthalene
and titanium isopropoxide are present'". We wish to report
here. inter uliu, on the "lithium hydride" complex
(COD), ,NiLi,H,(THF), (COD = 1,5-cyclooctadiene).
Reaction of binary nickel(0)-olefin complexes with metallic lithium yields well-defined dilithium-nickel-olefin complexes[' '1, for example as in eq. (a), containing reactive lit h i ~ m [ ~Thus
. ~ ] . (COD),NiLi,(THF), (2), which is relatively
soluble in THF or dimethoxyethane (-0.25 mol/l at room
temperature), reacts with molecular hydrogen (1 atm) even
at -- 60 "C. One H, per Li,Ni-unit is taken up with elimination of 0.5 COD/Li2Ni to produce the sparingly soluble
bright-yellow powder (3) [eq. (b)]'41.
THF
-- -30
~to_
0°C
_(COD),NiLi,(THF),
(2)
(1)
c12
(2)+'Hz
(a)
THF
-6010 -40°C
(COD), <NiLi2H2(THF),
t0.5COD
(b)
(3)
0
/
c2
Fig. 2 The bonding situation ar the site of the heterometal multicenter bond.
The molecular symmetry (CJ is perturbed by disorder of
the aliphatic carbon atoms of the complexed twelve-membered ring. The lithium atom which interacts only with two
perpendicularly oriented T H F ligands appears to be coordinatively unsaturated.
The 13C-NMR spectrum161of 1.3) in [DJbenzene exhibits a
total of eleven signals for the two identical twelve-membered
rings. Six can be assigned to methylene C-atoms (6=54.5,
44.0, 42.5, 41.8, 40.7. and 38.8 ppm, all t) and five to the Catoms of the complexed double bonds (6= 109.0, 85.6, 84.1,
78.7, and 75.7 ppm, all d). The failure to observe the sixth
olefinic C-atom (CI) is associated with its quaternary nature.
Received: March I , 1Y79 [Z 234a 11:)
German version: Angew. Chem. 91. 520 (1975)
_____
[ I ] K. Jonas. Angeu. Cheni. 87. 809 (1975): Angex Cheni. Int. Ed. Engl. 14. 552
(1975): K. R. Porrchke. Dissertation. Uiiiversitat Bochuin 1975
[Z] G. Wilke. Angew Chem. 75. 10 (1963): Angew. Chem. Int. Ed. Enpl. 2, 105
(1963).
131 Cell
data: a=926%(1). h=10.723(2). c=12.738(2) A: a=68.34(1).
p=66.78(1). -y=61.63(1)"; space group Pi. Z = I : 4048 reflections. 2574 of
which were not observed; decomposition during data collection; R = 0.103.
Atomic parameters and other data are availahle on request from the authors
( C. K.J.
141 D.J. Rrauer. C A'ruger. J. Orpanumrl. Chem. 44, 397 (1972): C. Kruyer. unpublished results
151 K. Jonas. D. J. Rrauer. C Kruger. P. J Roberrs, Y - i f . Tsar. J . Am. Chem.
SOC. 98, 74 (1976): D. J Rrauer. C. Kniger. P..I. Robem. Y.-H. T s a ~ Angew.
,,
(3) contains the unchanged ligand 1,5-cyclooctadiene, as
shown by reactions with cyclooctatetraene or CO in which
(3) is dissolved and cyclooctadiene is liberated in high yield.
Hydrogen is not evolved. (3) also dissolves in the presence of
organometallic Lewis acids such as (C,H,j,Al if COD is added. The Li and H atoms in (3) are transferred from the complex to the (C,H,),Al as lithium hydride [eq. (c)]. Both
Li[Al(C,H,),H]
(75% isolated as [Li(TMEDA),]"[Al(C,H,),H]".
TMEDA=N,N,N',N'-tetramethylethylenediamine) and (1) (90%) are formed in high yields.
Combination of equations (a), (bj, (c) gives a reaction sequence in which lithium, H,, and (C,H&Al produce
Li[Al(C,H,),H] stoichiometrically at - 30 "C and normal
pressure. An attempted nickel(0)-catalyzed synthesis of
Li[AI(C,H,),H], in which ( I ) , lithium, and (C,H,j,Al were
allowed to react at - 3 0 ° C was unsuccessful since (2) does
not complex with hydrogen in the presence of (C,H,),Al.
However, the (COD),Ni (1) re-formed according to eq. (c)
can be re-lithiated to start the cycle again. Thus it is possible
to synthesize Li[A1(C2H,),H] in stages pseudocatalytically in
a one-pot process.
I
_
_
['I
Dr. K . Jonas, Dr K R. Porschke
Max-Planck-lnstitut fur Kohlenforschung
Kaiser-Wilhelm-Platr I . D-4330 Mulheim-Ruhr (Germany)
Whereas pure lithium hydride prepared from lithium and
H, does not add to C:=C double bonds, the "lithium hydride" bound in (3) proves to be more reactive, e. g. with norbornene, propylene, or ethylene.
/3/
the position next to the oxygen atom, in both 4H-pyran
and 4-methyl-4H-pyran (1b)12bJ.
Subsequent treatment with methyl iodide, ethyl bromide, bromomethyltrimethylsilane, or chlorotrimethylsilane in petroleum ether affords 4% 2-methyl- (2a) and 22% 2-trimethylsilyl-4H-pyran
(2b), or 14% 2-ethyl- (2c), 23% 2-trimethylsilylmethyl- (2d)
and 48% 2-trimethylsilyl-4-methyl-4H-pyran
(Ze), respectively"'.
t
Ibf
a.-COD
I
1
+
COD,-CF4
(3) dissolves in an ethylene-saturated THF-solution
even at - 60 "C [eq. (01. Cooling the clear reaction solution
to -78 "C leads to the crystallization of (#a), or of
[Li(TMEDA),]@"C2H,Ni(C2H4)2]e
(46) if TMEDA is added,
while C,H,Li remains in solution. Reaction of C2H,Li and
(4a) with (C2H,),A1 and COD affords Li[Al(C,H,),] and
(COD),Ni (1) according to eq. (g); lithiation of (1) leads to
regeneration of (2) [eq. (a)]. For the preparation of (#a)/
C2HsLi from (2), there is a further route other than via (3)
[eqs. (b) and (01. This second route also involves two steps,
firstly displacement of the COD in (2) by ethylene, leading
to the sparingly soluble (5)[3,41
[eq. (d)] and, secondly, treatment of (5) with hydrogen [eq. (e)] to give a clear solution
from which (4a) crystallizes on cooling to - 78 "C.
Received: March I , 1979 [Z 234b IE]
German version: Angew. Chem. 91, 521 (1979)
CAS Registry numbers:
( 1 ) . 1295-35-8; (2). 70355-55-4; (4a), 60384-04-5; (5), 70355-56-5: C,H,Li, 91 149-4 Li, 7439-93-2; H,, 1333-74-0 C,H,, 74-85-1; (C,H,),AI, 97-93-8;
Li[AI(C,H,),], 2666-1 3-9; [Li(TMEDA),] [AI(C,H,),H] , 70377-86-5
+
[ I ] C. F. Huttig, A. Krajewskr, 2. Anorg. Allg. Chem. 141, 133 (1924): G. W
Matson, 7: P. Whaley, Inorg. Synth. 5, 10 (1957).
121 E. E. van Tamelen, P. B. Fechter. J. Am. Chem. Sac. 90,6854 (1968); S. Bonk,
M. C. Prrslopski, Chem. Commun. 1970, 1624.
131 K. Jonas. Angew. Chem. 87,809 (1975); Angew. Chem. Int. Ed. Engl. 14. 752
(1975).
141 K. R. Porschke, Dissertation, Universitat Bochum 1975; K. Jonas, Chemiedozententagung 1976, Regensburg.
15) K . Blum, Dissertation, Universitat Bochum 1978.
161 K. Jonas. K. R. Porschke, C. Kriiger, Y:H. Tsay, Angew. Chem. 88, 682
(1976). Angew. Chem. Int. Ed. Engl. J5, 621 (1976).
Metalation of Pyrans and Dihydropyridines: When is
an 8n-System Cost Effective?'"'
By Manfred Schlosser and Philippe Schneider"'
Powerful metalating agents''] such as butyllithium in the
presence of potassium tert-butoxide or trimethylsilylmethylpotassium promote slow hydrogen/potassium exchange at
____
[*I
Prof. Dr. M. Schlosser, Dip1.-Chern. P. Schneider
Institut de Chimie Organique de I'Universite
Rue de la Barre 2, CH-1005 Lausanne (Switzerland)
[**I This work was supported by the Schweizerischer Nationalfonds zur Forderung der wissenschaftlichen Forschung (Project 2.467.0.75 and 2.693.0.76).
Anyew. Clii~ni.I n t . Ed. Enyl. 18 (1979) No. 6
0 Verlay
(2a), R = H ,
(Zb), R = H,
( 2 ~ ) , R=CH3
( 2 d ) , R=CH3,
(2e), R=CH3,
(la), R=H
(Ib), R=CH3
E=CH3
E = Si(CH3)3
E=CZH~
E=CHZS~(CH~)~
E=Si(CH3)3
Thus, upon treatment with organometallic reagents the
pyrans (la) and ( l b ) behave like 3,4-dihydro-2H-pyran, in
which the olefinic hydrogen adjacent to the oxygen atom
can-again slowly and accompanied by side reactions-be
In contrast, the openreplaced by lithium and
ring analogs (3a) and (36) are rapidly and exclusively deprotonated at the double-allylic
R
R
(3a), R = H
(36), R=CH3
Upon reaction with butyllithium and potassium tert-but(4b)iS1is
oxide in pentane, 1,4-dimethyl-l,4-dihydropyridine
also metalated only at the position adjacent to the heteroatom. Subsequent reaction with deuterium oxide or chloromethylsilane leads to 82% of the 2-deuteriated (5b) or 41% of
the 2-trimethylsilylated derivative (54, respectively. On the
other hand, the homologous 1-methyl-I ,4-dihydropyridine
( 4 ~ ) " 'can be deprotonated, depending on the selected metalating agentI6', either again at the "geometrically a~idified"1'~
olefinic position or, alternatively, at the "electronically acidified"['] methylene group. Reaction with butyllithium and
potassium tert-butoxide in pentane followed by addition of
chlorotrimethylsilane afforded 3% 1-methyl-2-trimethylsilyl1,4-dihydropyridine (Sa) as the sole volatile product besides
starting material and resins[31.Using trimethylsilylmethylpotassium in tetrahydrofuran, however, we were able for the
first time to remove aproton from the allylicposition of a dihydropyridine derivative and thus generate an organometallic 8 ~ system[*].The intermediate, moderately stable at - 50 "C,
reacts with methyl iodide or chlorotrimethylsilane to give, respectively, a 1 :1 mixture of 1,2-dimethyl-1,2-dihydropyridine (6a) and 1,4-dimethyl-l,4-dihydropyridine(7a) in 55%
yield or l-methyl-4-trimethylsilyl-1,4-dihydropyridine (7b)
(6%) [3. '1.
The differing behavior of the two N-methyldihydropyridines (4a) and (46) is not particularly surprising. Introduction
Chemie, GmbH, 6940 Weinheim, 1979
05 70-0833179/0606-0489
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