COMMUNICATIONS TO THE EDITOR
2338
Vol. 85
TABLE I1 highly optically stable through a sequence of reactions REDUCTION OF ACETOPHENONE WITH ALUMINUM ISOPROPOXIDE summarized in Scheme I. TRIMER' SCHEMEI
Time
K e t o n e composition, mole yo Acetophenone Acetone
*
a-Phenylethanol yield as
yo of
theoretical yield
Molar ratio, a-phenylethanol acetone
0 100 0 0 .. 10 min. 91.9 8.1 1.4 0.17 20 min. 87.1 12.9 3.7 .29 6.6 ,28 40 min. 76.7 23 3 60 min. 69.6 30.4 10.4 ,34 .50 16 hr. 28.1 71.9 35.9 40 hr. 26.2 73.8 42.6 .58 64 hr. 24.3 75.7 46.7 .62 a Temperature 31.4' for first hour (in n.m.r. probe) and then 25"; initial concentrations in 50 mole yo benzene and isopropyl alcohol were acetophenone, 0.893 M ; aluminurn isopropoxide, 0.653 M (calculated as monomer).
If i t is assumed that the trimer and tetramer react by the same type of mechanism, these results then show that the ketone coordinates not with a l u m i n u m alkoxide monomer formed by dissociation but directly with the trimer or tetramer by expansion of the coordination number of a l u m i n u m . The reduction could not be due to a small amount of monomer in rapid equilibrium with both trimer and tetramer because the MPV reaction is much faster than the trimer-tetramer interconversion under similar conditions. Further, the reactivity cannot be due to catalysis by a small fraction of monomer not in equilibrium with the polymeric forms because a fairly large fraction of aluminum a-phenylethoxide is formed (probably as a mixed alkoxide). The different reactivities of the slowly interconverted polymeric forms of aluminum alkoxides, and the slow alkoxide exchange with alcohols probably constitute serious sources of error in the interpretation of previously published kinetic studies of the MPV reacti~n.~.~ LiPV reductions can thus be achieved much more rapidly and under much milder conditions than those generally employed by using aluminum isopropoxide trimer as a reagent rather than as a catalyst. This technique is aided by the miscibility of this material with rnost organic solvents. The reaction can be forced to completion by removal of the acetone a t reduced pressure and the product recovered by hydrolysis of the aluminum alkoxide. Acknowledgment.-This work has been supported in part by Grant GRI 08502-02 from the National Institutes of Health. (4) I, 51. Jackman a n d A K . M a c b e t h , J . Chem. Soc., 3252 (1952); M . S. Bains and D . C. Bradley, Chem. I n d (London), 1032 (1961).
CHEMISTRY DEPARTMEXT V. J. SHINER, JR. INDIASAUSIVERSITY D. WHITTAKER BLOOMISGTON, INDIASA RECEIVEDMARCH30, 1963
Displacements at Asymmetric Germanium.
Methyl-a-naphthylphenylgermyllithium and its Derivatives Sir: The resolution of asymmetric organogermanium compounds has recently been We now wish t o report on the chemistry and stereochemistry of some displacements a t germanium which occur with conMethyl-a-naphthylphenylsiderable specificity. germyllithium has been prepared and shown to be (1) R W . B o t t , C Eaborn and t. D. Varna, Chem. I n d . ( L o n d o n ) , 614 (1963) ( 2 ) A G Brook and G . J . D. Peddle, J . A m . Chem. Soc., 86, 1869 (1963)
( - )GeH [a]D
R
i
n-BuLi
*
COX
CH2Ri
+GeLi +( +)$eCOOH +(+)G*eCOOMe R
R
-25.5'
Cla
( +)$ea LiAlHi
(-)GeH
( - )GeOMe
(+);eC--Ph*
I
[ a ] -18.5' ~
OH
*
( - )GeH
R I
= =
retention inversion
*
Ge
[a]D
=
-22.5"
asymmetric germanium bearing methyl, a-naphthyl, and phenyl groups.
Metalation of (- )methyl-a-naphthylphenylger* mane, ( -)GeH3 with one equivalent of n-butyllithium in ether a t room temperature over 30 min. gave a dark * brown solution of GeLi, which on treatment with water * gave (-)GeH containing 8670 of the (-) enantiomer. * Treatment of GeLi with benzophenone gave in 6S% yield ( + ) G k O H P h 2 ,
[~]?OD
G.3", m.p. 132-134', and
carbonation of deLi gave ( + ) G k O O H , free of ( - ) GEH, [ a l Z z5.15', ~ m.p. 9G.5-9S0, dec. 110' in 66% yield. Esterification of the acid with diazomethane * gave an oil, (+)GeCOOMe, [ c Y ] ? ~ D3.06', which on thermal rearrangement from 230-270" gave 95% of * (-)GeOMe, [ a I z 6-9.75", ~ m.p. 54-59', and carbon monoxide. Reduction of the methoxygermane with * lithium aluminum hydride gave (-)GeH in 97yo yield, [LY]??D -22.5", m p . 72-73.5" containing 94% of the original ( - ) enantiomer. Thus each of the four consecutive displacements a t gernianiurn occurred with esSimilarly (- )GeH * 1~ on chlcrination gave l O O ~ Cof (+)GeCl, [ a ] 2 0+6.32", sentially complete stereospecificity.
$
m.p. 68-69" which on reduction gave ( + ) G e H , [ a I z 7 ~ +24.9", in 99% yield, another kiyalden cycle with high over-all stereospecificity. * All of the reactions except the reduction of GeCl are believed to take place with retention of configuration a t germanium.
If so, then (-)
