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Improved Carbon-Carbon Linking by Controlled Copper Catalysis.

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(9)
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densationofaikyl iodidewith Grignard reagent in the presence
of dilithium tetrachlorocuprate as catalyst produced yields
which were hardly satisfactory (63% of decane) in view of
our actual aim of preparing optically active dipropylcycloprostarting from (R,R)-bis(hydroxymethy1)cyclopane (2)
propane ( I ) (X = OH).
/
c=c
H3C‘
’OC&
of the zwitterions arise in the ‘U’-conformations (3) and
(6), i.e., in the state where the Coulomb potential of the
charge centers is lowest; a donor-acceptor interaction between
the electrophilic and nucleophilic centers may contribute to
the stabilization of the spatial arrangement.
In acetonitrile the zwitterions (3) and (6) undergo cyclization
to (2) and ( 5 ) and cis-trans-isomerization by rotation in
the proportions f :5 and 1 :4, respectively, which correspond
to 16% and 20% of non-stereospecifically formed cyclobutanes”].
The stereospecificity of acetai formation in alcohol is higher.
Clearly a configuration-stabilizing interaction of the zwitterion
and alcohol occurs at an early stage. The concurring 2 f2-cycloaddition in alcohol is strikingly more stereospecific than
the one in acetonitrile. In alcohol the ring closure to the
cyclobutane has a chance only if the zwitterions are formed
in the conformations (3) and (6) that are ideal for cyclization.
Some “badly oriented” zwitterions, nevertheless, are formed
and are trapped by the alcohol as shown by comparison
with the 98-99% stereospecificity of acetal formation on
ethanolysis of the pure methoxycyclobutane (2) and on methanolysis of the ethoxycyclobutanes ( 1 1 ) and (12) (Table 1).
The comparatively slow ring opening of the cyclobutanes“]
produces almost wholly “ideal” zwitterions whose reaction
with alcohol is highly stereospecific.
Our attempts to improve the method were guided by the
following considerations:
I ) Copper(1) compounds13] prefer tetragonal coordination.
Cuprates of the type MCuXRC4.51 (M = MgX, Li, etc. ; X = halide, alkoxide, or organic group) acquire the stable tetracoordination by self-association or by association with another
organometallic species that may be present in excess. It is
important that the mixed complex[61 expected in our case,
i.e. (3), be allowed to form without interference.
2) The role of initiator is assumed by the monomeric cuprate
or the cation i 4 ) derived therefrom which, as an electron-deficient compound, can undergo carbene-like ((6)) insertion into
R‘MgBr; BrMgCuBrR‘
4
L
R-R’
[MgOTos]
(3)
a CX bond (e.g. to give ( 5 ) ) . Insertion should be facilitated
by leaving groups which, like p-toluenesulfonates ( 7 ) , are
capable of 1,4-interactions.
The configuration of the acetals ( 4 ) and (7) must be proved
by X-ray structure analysis. As shown in Scheme 1 and in
(13) we favor selective attack of the alcohol on the carboniumoxonium center “from above” rather than reaction via the
hydrogen bonded chelate ( 1 4 ) which should lead to compounds that are epimeric at C-1.
Received: October 25,1973 [Z 946b IEJ
German version: Angew. Chem. 86.48 (1974)
[ I ] For isolation and determination of structure of ( 4 ) and (7) see R.
Huisgen, R. Schug, and G. Sreiner, Angew. Chem. 86, 47 (1974); Angew.
Chem. internat. Edit. 13, 80 (1974).
[Z] R. H u i s g m and G. Srrinvr, J. Amcr. Chem. SOC. 95. M54, 5055 (3973).
Improved Carbon-Carbon Linking
by Controlled Copper Catalysis[**J
By Gerd Fouquet and Manfred Schlosser[*l
During a search for the simplest and most effective pathway
from I-octanol to decane most of the conventional C-C
linking reactions failed. Even a new variant“] involving con[*] Prof. Dr. M. Schlosser and Dr. G. Fouquet
Institut de Chimie Organique de I’UniversitG
Rue de la Barre 2, CH-100s Lausanne (Switzerland)
This work was supported by the Schweizerischer Nationalfonds (Project
No. 2.593.71). Thanks are also due to BASF, Ludwigshafen, for supplying
starting materials.
[**I
82
As shown in Table 1, a “catalyst breeding” step (mixing of
Grignard reagent and copper catalyst at -78°C followed
by gradual warming to room temperature, below which no
condensation occurs) and use of p-toluenesulfonates instead
of iodides or even bromides leads to a striking improvement.
The Grignard component can be varied at will. In contrast,
only primary p-toluenesulfonates react well, while secondary
and tertiary ones give poor yields of product -if any-presumably owing to steric hindrance of insertion. The smooth
reaction of (1) (X=OTos) to give (2) also confirms that
no carbocationic, -radical, or -anionic intermediates are
involved.
Surprisingly, it also proved possible to replace acetate
groups[’ occupying allylic and benzylic positions by the
hydrocarbon moiety of Grignard compounds, apparently
because acetates can likewise exhibit a chelating action. Thus
trans-crotyl acetate was converted regio- and stereoselectively
into trans-2-octene (8) (88 %).
Angew. Chem. intrmnat. Edit.
1 Vol. 13 (1974) i
No. I
Table 1. Condensation reactions between p-toluenesulfonates (R-OTos) and
Grignard compounds ( R ' - M u ) .
-
R in
R-OTos
R' in
R'-MgBr
[d]
R-R'
Yield
[b]
[%I
[c]
19
98
90
98
96
0
51
0
3
99
[a] OTs= OS01-ChH4-CH3.
[b] Grignard reagent always added in excess (1.4 equiv.).
[c] Glc analyses. internal reference substance: calibration factors for peak
area correction: standard deviation f 3 %.
[d] I 1 ), X = OTos.
MgBr
YO C C+L,v--v-A
H,
0
[8] Identity and purity were checked by elemental analyscs, vpc, as well
and "C-NMR and infrared spectra.
as mass, 'H-,
[9] Corrected for an impurity of 5'la cis isomer present in the starting
material.
[lo] Formation of this normal acetate reaction product may be even further
reduced (<5"/0) if larger amounts of CuI ((.a. I equiv.) are used instead
of LlzCUCI,.
[ill Note added in proof: Lithium dialkylcuprates can also undergo condensation reactions with tertiary allylacetates; however, they overwhelmingly
involve attack at the vinylogous position and allylic shift of the double bond
(P.Rona, L. Tdkes, J . Tremble, and P . Crabbh, Chem. Commun. 1969. 43;
R. J . Anderson, C . A . Henrik, and J . B. Siddall, J. Amer. Chem. SOC 92, 735
(1970)).
Convenient Synthesis of Vinylsilanes and Their Use
in Ketone Synthesis[**]
By Bengt-Thomas Grobvl and Dieter Seebach[']
Vinylsilanes ( I ) can be converted into carbonyl derivatives
( 3 ) via epoxides (2)[11. Thus all C-C coupling reactions
in which vinylsilanes are formed represent potential methods
for producing carbonyl compounds.
(8)
Similarly, cis-2-octene (50%)was obtained from cis-crotyl acetate.
2,2-Dimrthyldecane:
Octyl p-toluenesulfonate (40 mmol) in tetrahydrofuran solution (50 ml) was treated at - 78' C with tert-butylmagnesium
bromide (56mmol in 32ml of diethyl ether) and LiZCuC14[']
The reaction mixture
(0.2 mmol in 2 ml of tetrahydrof~ran)[~].
was allowed to warm to room temperature during 2 h and
stirring was continued for other 12h. An aliquot sample was
withdrawn and, after decane had been added as an internal
standard, subjected to glc analysis. The main part of the
reaction mixture was acidified with 2 N sulfuric acid, washed
twice with water (2 x 50ml), dried (CaS04), and evaporated.
Distillation and rectification (b. p. 77-78 C/15 torr) yielded
5.1 g (75%) of pure 2,2-dimethylde~ane[~].
trans-2-Octene :
In the same manner trans-~rotylacetate[~~
( 100mmol), n-butylmagnesium bromide (140 mmol), and Li2CuCI4 (0.2 mmol)
were mixed in a total volume of 50ml of tetrahydrofuran
and 40ml of diethyl ether. A 62% yield of trans-2-0ctene[*.~I
(b. p. 120-122°C) was isolated by spinning band column
distillation ; in addition 9% of 5-methyl-5-nonanol (b.p. 78 to
80 C/2 torr) was obtained. According to glc (6 m 15 Yosilicone
rubber SE-30, 100'C; 2 m 5%+25Y0 AgN03+diethylene
glycol, 30 "C) the yields amounted to 88 % and 11%, respectively[''].
Received: September 10,1973 [Z 947 I€}
German version: Angew. Chem. 86, 50 (1974)
[ I ] M . Tamiira and J . Kochi, Synthesis 1971, 303; see also H. Gilman, R.
G. Jonus, and L. A. Woods, J. Org. Chem. 17, 1630 (1952).
[2] M . Schlossvr and G. Fotryrrut, Synthesis 1972, 200: Chem. Ber., in press.
[3] The catalytically active species appears to be a copper(1) derivative:
Cut is as effective as Li,CuCI;
[4] H. Giiman, R. G. Jones, and L. A . Woods, J. Org. Chem. 17, 1630 (1952);
H. 0. House, W L. Respess, and G. M . Whitesides, ibid. 31, 3128 (1966);
G. Wittig and G . Klar, Liebigs Ann. Chem. 704, 91 (1967); E . J . Corey and
G . H . Posner, J. Amer. Chem. Soc. 89,3911 (1967); 90,5615 (1968);G. H. Posner
and C . E. Whitten, Tetrahedron Lett. 1973, 1815.
[5] Reviews: J . F. Normont, Synthesis 1972, 63: see also: W Tochrrrmann,
Angew. Chem. 78, 355 (1966). Angew. Chem. internat. Edit. 5 , 351 (1966):
G. W t i g , Quart. Rev. t h e m . SOC.20, 191 (1966): G . H. Posnvr, Org. React.
19, I (1972).
[6] Review: M . Schlosscrr Struktur und Reaktivitat polarer Organornctalle.
Springer-Verlag, Heidelberg 1973, particularly pp. I 1-16.
[7] Subsequent addition of thc p-toluenesulfonate, t2.y. after 3 h at 0 C ,
leads to thc same result.
Angew. Chem. internat. Edit. 1 Vol. 13 (1974)
1 No.
1
We now describe new 2-silyllithium reagents (8) and ( 9 )
from which vinylsilanes (10)--( 22) having different substitution patterns are accessible by simple C-C bond formation
or by Peterson olefination.
\I
-Si\
(3Si)2 CHz
C=C Hz
Br/ (6)
I
f 71
1
r<Li
i
Compound (8)r2J is produced from tris(trimethylsily1)methyllithium (4)c3I which is first converted into the olefin (5)14]
in 70% yield by a Peterson reactionC5! Compound ( 5 ) can
be transformed into (6)[61,which is subjected to bromine-lithium exchange with tert-b~tyllithium[~~.
The substituted reagents of type (9a) are prepared in more than 900/;, yield
byaddition[2a.81ofalkyllithium compounds R'Li to ( 5 ) . Solutions of reagent (9b)c3"] are also obtained in yields exceeding
90YOby metalation of (7) in an improved process.
Compound (8) was subjected to the action of alkyl halide,
aldehyde, or ketones, whereupon the products ( l o ) were
[*] DipLChem. B.-Th. Grobel and Prof. Dr. D. Seebach
Fachbereich 14 Chemie, Institut fur Organische Chemie der Universitdt
63 Giessen, Ludwigstrasse 21 (Germany)
[**I This work was supported by the Fonds der Chemischen Industrie:
B.-Th. G. wishes to thank the Studienstlftung des Deutschen Volkes for
a grant.
83
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