COMMUNICATIONS
tallographic data (excluding structure factors) for the structures
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication
no. CCDC-179-100685. Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road, Cambridge
CB21EZ, UK (fax: (44)1223-336-033; e-mail: deposit@ccdc.cam.
ac.uk).
R
R
O
MLn
R
R
LnM
MLn
R
O
O
MLn
M
Ln
A
B
C
[
[
8] Examples of trigonally coordinated Li: a) M. F. Lappert, M. J. Slade,
A. Singh, J. L. Atwood, R. D. Rogers, R. Shakir, J. Am. Chem. Soc.
crucial in order to achieve high reactivity, particularly in the
case of less reactive organometallic reagents. In this context,
we became interested in designing new molecules of type C
with two metallic centers that would permit simple alkylation
of carbonyl compounds with otherwise less reactive alkylme-
tal species.[ Here we report initial results with the modified
bis(dialkylaluminum) reagent 1, an efficient alkyl-transfer
1983, 105, 302 ± 304; b) L. M. Engelhardt, B. S. Jolly, P. C. Punk, C. L.
Raston, B. W. Skeleton, A. H. White, Aust. J. Chem. 1986, 39, 133;
c) P. G. Willard, M. A. Nichols, J. Am. Chem. Soc. 1991, 113, 9671 ±
9673; d) H. Görls, B. Neumüller, A. Scholz, J. Scholz, Angew. Chem.
1995, 107, 732 ± 735; Angew. Chem. Int. Ed. Engl. 1995, 34, 673 ± 676.
9] The negative charge of the aminopyridinato ligand is not localized on
the amido nitrogen atom.
3]
[
3
10] Compound 5 is not accessible by transmetalation with YCl and three
equivalents ªTMS-ApLiº (ether/pyridine); this procedure affords
compound 1 instead.
[4]
system for aldehydes (Scheme 1).
[
11] The ªateº complexes are very often observed for lanthanide ions:
a) H. Schumann, Angew. Chem. 1984, 96, 475 ± 493; Angew. Chem.
Int. Ed. Engl. 1984, 23, 474 ± 492; b) R. D. Köhn, G. Kociok-Köhn, H.
Schumann in Encyclopedia of Inorganic Chemistry (Ed.: R. B. King),
Wiley, New York, 1994; c) C. J. Schaverien, Adv. Organomet. Chem.
1
or 2
R1
R
(R2AlOAr)
R1 CHO
3
+
R1 CH OH
5
2
CH2Cl2
OH
1
994, 36, 283 ± 362; d) F. T. Edelmann in Comprehensive Organo-
4
metallic Chemistry II (Eds.: E. W. Abel, F. G. A. Stone, G. Wilkinson),
Pergamon, Oxford 1995; e) H. Schumann, J. A. Meerse-Marktschef-
fel, L. Esser, Chem. Rev. 1995, 95, 865 ± 986.
R2Al
AlR2
O
AlR2
O
O
[
12] Sincere thanks are due to the referee who provided this information.
Me
Me
Me
Me
1
2
Scheme 1. Alkylation of aldehydes with dialkylaluminum reagents.
1
Treatment of benzaldehyde (3; R Ph) with one equiv-
alent of Me Al in CH Cl at � 788C gave a long-lived
Rate Acceleration in Nucleophilic Alkylation
of Carbonyl Compounds with a New Template
Containing Two Metallic Centers**
3
2
2
monomeric 1:1 complex that gradually decomposed to 1-
1
[5]
phenylethanol (4; R Ph, R Me) on warming to � 208C.
Use of (2,6-dimethoxyphenyloxy)dimethylaluminum (2, R
2
Takashi Ooi, Makoto Takahashi, and Keiji Maruoka*
Me) instead of Me Al significantly retarded the rate of
3
alkylation under similar reaction conditions. Even use of
excess 2 (2 equiv) failed to yield methylation product 4 at
The nucleophilic addition of reactive organometallic re-
agents to carbonyl compounds is undoubtedly one of the most
thoroughly investigated of all organic transformations be-
cause of sustained interest in its mechanism and selectivity, as
well as numerous applications to a variety of syntheses in the
fields of natural products, pharmacology, and material sci-
� 208C. In marked contrast, however, methylation of benzal-
dehyde proceeded quite smoothly with one equivalent of 2,7-
dimethyl-1,8-biphenylenedioxybis(dimethylaluminum) (1;
R Me) at � 208C to furnish after 4 h 1-phenylethanol (4;
1
[6]
R Ph, R Me) in 84% yield. With higher alkyl deriva-
tives of 1 (R Et, Hex), alkylation was accompanied by
concomitant formation of reduction product 5, and different
aldehydes gave equally good results (Table 1).
[
1]
ence.
The preferred transition state for addition of Grignard and
organoaluminum reagents is often a cyclic six-membered
array (A) that contains a carbonyl group and two molecules of
[
2]
organometallic reagent. With the same reactants in a 1:1
ratio, a four-centered transition state (B) is also conceivable,
although alkylation proceeds more slowly by this route.
Hence, facilitation of the six-membered transition state A is
Table 1. Alkylation of aldehyde 3 with dialkylaluminum reagents.[a]
Entry R1
R
Reaction conditions
Yield of 4 and 5 [%][b]
[
a]
[
8C, h]
Use of 1
Use of 2
1
2
3
4
5
6
7
Ph
Ph
Ph
cHex
cHex
cHex
Me � 20,4
84
0
[
*] Prof. K. Maruoka, M. Takahashi, Dr. T. Ooi
Department of Chemistry, Graduate School of Science
Hokkaido University
Et
� 78,1; � 40,2
71 (11)
60 (36)
63
52 (22)
50 (20)
86
10 (2)
6 (5)
Hex � 78,1; � 40,1.5
[
c]
Me � 78,1; � 40,3; � 20,3
4
Sapporo, 060 (Japan)
Et
Et
� 78,2; � 40,3
10 (9)
3 (2)
< 1
Fax: (81)11-746-2557
[
d]
� 78,2; � 40,3
E-mail: maruoka@sci.hokudai.ac.jp
C
9
H
19
Me � 20,4.5
[
**] This work was partially supported by the Asahi Glass Foundation, the
Akiyama Foundation, the Suhara Memorial Foundation, and a Grant-
in-Aid for Scientific Research from the Japanese Ministry of
Education, Science, Sports, and Culture.
[a] Alkylation was carried out under the reaction conditions cited with 1
(1 equiv) or 2 (2 equiv) in CH
2
Cl
2
. [b] Yield of 5 in parentheses. [c] Aldol
2 2
product through self-condensation. [d] Use of dilute CH Cl
solution.[
7]
Angew. Chem. Int. Ed. 1998, 37, No. 6
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1433-7851/98/3706-0835 $ 17.50+.50/0
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