Astonishing alkylation and unusual reduction reactions of anionic titanium(II) isopropoxide complexes: Evidence for SET processes in transition-metal oxidative additions

Article abstract of DOI:10.1002/1099-0682(200212)2002:12<3091::AID-EJIC3091>3.0.CO;2-Y

A mixture of titanium(II) isopropoxide and lithium isopropoxide (1:2), generated in THF by the treatment of titanium(IV) isopropoxide with two equivalents of n-butyllithium, has been shown to be an unexpected alkylating agent as well as an unusual reducing agent for a wide variety of organic substrates. Since titanium(II) isopropoxide, which is free of any lithium isopropoxide, neither causes alkylation of any of the same substrates nor is such a powerful reductant, it is proposed that the lithium isopropoxide activates titanium(II) isopropoxide for such unusual reactions by the formation of the lithium salt coordination complex Li₂Ti[OiPr]₄. Illustrative of the unprecedented alkylations are the transformations, after hydrolysis, of various substituted benzonitriles to isopropyl-substituted phenyl ketones, of (dichloromethyl)benzene to, principally, 2-methyl-1-phenyl-1-propene and of (trichloromethyl)benzene to isopropyl phenyl ketone. By comparing the reducing actions of Li₂Ti[OiPr]₄ and Ti[OiPr]₂ individually, it has been shown that, generally, the lithium salt is the more powerful reductant for epoxides, benzylic halides and conjugated olefins. From the reactions of Li2Ti[OiPr]4 with the benzonitriles, styrene, the isomeric stilbene oxides and cis-stilbene, cogent evidence is marshaled for the operation of SET processes, sensitive to steric hindrance, in such alkylations and reductions. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.

Full text of DOI:10.1002/1099-0682(200212)2002:12<3091::AID-EJIC3091>3.0.CO;2-Y

SHORT COMMUNICATION
Astonishing Alkylation and Unusual Reduction Reactions of Anionic
Titanium(II) Isopropoxide Complexes: Evidence for SET Processes in
Transition-Metal Oxidative Additions[
‡]
[a]
[a]
John J. Eisch* and John N. Gitua
Keywords: Titanium / Subvalent compounds / Oxidative addition / Alkylation / Electron transfer
A mixture of titanium(II) isopropoxide and lithium isopropox- propyl-substituted phenyl ketones, of (dichloromethyl)ben-
ide (1:2), generated in THF by the treatment of titanium(IV
isopropoxide with two equivalents of n-butyllithium, has (trichloromethyl)benzene to isopropyl phenyl ketone. By
been shown to be an unexpected alkylating agent as well comparing the reducing actions of Li Ti[OiPr] and Ti[OiPr]
as an unusual reducing agent for a wide variety of organic individually, it has been shown that, generally, the lithium
)
zene to, principally, 2-methyl-1-phenyl-1-propene and of
2
4
2
substrates. Since titanium(II) isopropoxide, which is free of
any lithium isopropoxide, neither causes alkylation of any of
the same substrates nor is such a powerful reductant, it is
salt is the more powerful reductant for epoxides, benzylic
halides and conjugated olefins. From the reactions of
Li Ti[OiPr] with the benzonitriles, styrene, the isomeric
2 4
proposed that the lithium isopropoxide activates titanium(II
isopropoxide for such unusual reactions by the formation of
the lithium salt coordination complex Li Ti[OiPr] . Illustrative
of the unprecedented alkylations are the transformations,
after hydrolysis, of various substituted benzonitriles to iso-
)
stilbene oxides and cis-stilbene, cogent evidence is mar-
shaled for the operation of SET processes, sensitive to steric
hindrance, in such alkylations and reductions.
( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany,
2002)
2
4
Introduction
clearly why 5 should be viewed as an oxachromacyclopro-
pane rather than as the π-complex 6. Were the π-complex 6
The oxidative addition of subvalent transition metals or involved in the reaction with CO
, then simple ligand dis-
to 7 should have ensued
2
2
n
metal salts, M L (1), where n is the oxidation number, to placement and reduction of CO
t
x
π-bonded organic substrates (2) with the formation of a (Scheme 1). Instead, the observed products of deuterium
metallacyclic intermediate (3) has been termed epimetall- oxide cleavage (8) and of carbonation (9) are unambiguous
ation [Equation (1)].[
2]
proof for the presence of a CϪCr bond in 5.
In exploring the applicability of epimetallation for or-
ganic synthesis, we have recently generated titanium() iso-
propoxide (10) according to Equation (2) and have em-
1) ployed 10 for the epimetallation of terminal alkenes, al-
(
[
4]
kynes and selected carbonyl derivatives.
Since metallacycle 3 is one extreme of resonance struc-
tures ranging to the other extreme of a π-complex structure
(
2)
4
2
, the term epimetallation implies that the adduct of 1 and
displays chemical reactions in better accord with 3, pos-
sessing two sigma CϪM bonds, than with 4. The chemical
t
behavior of 5 — the adduct of benzophenone and
ϩ
Ϫ
[3]
[2]
Li CrH — towards D O and towards CO2 illustrates
2
2
Particularly noteworthy are the by-products formed in
the production of 10, namely lithium isopropoxide (11),
which remains in solution regardless of whether the reac-
[
‡]
a]
Organic Chemistry of Subvalent Transition Metal Complexes,
[
1]
24. Part 23: Ref.
[
Department of Chemistry, The State University of New York tion is conducted in hexane or THF, and the one equivalent
at Binghamton
of 1-butene (12) which is epimetallated in situ by 10 with
the formation of 14 (Scheme 2). The presence of 14 was
demonstrated by its chemical trapping with benzonitrile
P. O. Box 6016, Binghamton, New York 13902Ϫ6016 U.S.A.
Fax: (internat.) ϩ1-607/777-4865
E-mail: jjeisch@binghamton.edu
Eur. J. Inorg. Chem. 2002, 3091Ϫ3096  2002 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 1434Ϫ1948/02/1212Ϫ3096 $ 20.00ϩ.50/0 3091

J. J. Eisch, J. N. Gitua
SHORT COMMUNICATION
Scheme 1
(
15) to provide 16, whose subsequent hydrolysis yielded n- the lithium chloride formed is a much weaker base and
[4]
butyl phenyl ketone (17). Only if the solvent is removed more ionic salt and precipitates completely from the mix-
by warming and reduced pressure can 14 be decomposed.
ture. When this Ti(OiPr) , free of lithium isopropoxide, was
2
heated with benzonitrile in toluene and then hydrolyzed,
analogous to the reaction in Scheme 3, no trace of 18 was
[
7]
found whatsoever. Thus, a combination of 10 and 11 is a
prerequisite for the formation of isopropyl phenyl ketone
(18) from benzonitrile (15).
Scheme 2
Results and Discussion
Scheme 3
In order to learn whether titanium() isopropoxide itself,
free of any of the adduct 14, could epimetallate benzonitrile
(15), a solution of 10 generated in THF was freed of solvent
under reduced pressure at 70°. To the black residue of 10
and 11 an equivalent of benzonitrile in toluene was then
added and the solution heated at reflux. To our astonish-
ment, upon hydrolytic workup such a reaction mixture gave
(
3)
In establishing the role of 11 in activating 10 for this un-
usual reaction, it should be noted that titanium() salts
form anionic complexes with alkali metal salts. Therefore,
92% of isopropyl phenyl ketone (18) but only a small
amount of 17 and a trace of 2,2-dimethyl-1,3-diphenyl-1,3-
[8]
[
5]
propanedione (19) [Scheme 3, Table 1]. The formation of
8 raised the possibility that heating solutions of 10 might
1
0 and 11 can be expected to be in equilibrium with com-
1
plexes such as 23 [Equation (4)].
have produced an isopropylmetallic agent 20, which would
then have added to 15 to yield 21, a prehydrolysis interme-
diate to the observed final product. That the lithium isopro-
poxide by-product 11 plays an essential role in this unexpec-
ted reaction was demonstrated in the following way. Re-
cently we have reported that titanium() isopropoxide, free
(4)
That four isopropoxyl groups can be sterically accom-
of lithium isopropoxide, can be prepared by treating tita- modated around the titanium() center in 23 is corrobor-
nium dichloride diisopropoxide (22) in hexane with two ated by the existence of stable titanium() isopropoxide.
equivalents of n-butyllithium[ [Equation (3)]. In this case, One possibility for the formation of the requisite isopropyl-
6]
3092
Eur. J. Inorg. Chem. 2002, 3091Ϫ3096

Evidence for SET Processes in Transition-Metal Oxidative Additions
Table 1. Reactions of the titanium() isopropoxide-lithium isopropoxide complex (23) in THF with organic substrates
SHORT COMMUNICATION
Entry
1
Substrate[a]
Products
Yield (%)[b]
Benzonitrile (15)
Isopropyl phenyl ketone (18)
Butyl phenyl ketone (17)
92
7
1
90
10
99
1
2
,2-Dimethyl-1,3-diphenyl-1,3-propanedione (19)
Isopropyl 2-methoxybenzonitrile ketone
,3-Bis(p-anisyl)-2,2-dimethyl-1,3-propanedione
Isopropyl 4-methoxyphenyl ketone
,3-Bis(p-anisyl)-2,2-dimethyl-1,3-propanedione
2
3
2-Methoxybenzonitrile (26)
4-Methoxybenzonitrile (27)
1
1
4
5
2,4,6-Trimethylbenzonitrile (28)
(Dichloromethyl)benzene (29)
No Reaction
2-Methyl-1-phenyl-1-propene (30)
trans-Stilbene
Benzyl chloride
Isopropyl phenyl ketone
Ϫ
40
1 6
32
8
1
,2-Dichloro-1,2-diphenyl ethane
Isopropyl phenyl ketone (18)
,1,2,2-Tetrachloro-1,2-diphenylethane
4
6
(trichloromethyl)benzene (30a)[c]
64
30
6
97
3
55
45
40
91
9
100
30
5
1
trans-1,2-Dichlorostilbene
Dibenzyl (40)
Toluene
7
8
9
Benzyl chloride (31)[d]
9-Bromofluorene (32)[d]
Fluorene
9
Anisole
,9ЈBifluorenyl
4-Bromoanisole (38)
cis-Stilbene oxide (33)[
d]
trans-Stilbene (36)
cis-Stilbene (35)
trans-Stilbene (36)
cis-Stilbene (35)
Dibenzyl (40)
trans-Stilbene (36)
Dibenzyl (40)
Dibenzyl (40)
Polystyrene
1
0
1
1
1
2
trans-Stilbene oxide (34)[d]
Diphenylacetylene (37)
1
3
cis-Stilbene (35)
35
25
25
100
1
1
4
5
trans-Stilbene (36)
Styrene (38)
[
a]
2
All reactions involved 10.0 mmol of Ti(OiPr) containing the LiOiPr by-product and 5.0 mmol of the organic substrate in 40 mL of
[b]
1
THF at 25 °C for 24 h unless otherwise specified.
Percent yields of products were obtained from the integrated H NMR spectra;
recovered starting substrate ϭ 100% Ϫ% of products. [ The reaction was conducted at reflux for 4Ϫ8 h. The reaction was conducted
c]
[d]
at 25 °C for 12 h.
ating agent 20 would be an intraanionic oxidative addition Equation (2). The resulting products are tabulated in
that might occur upon heating 23 that would produce isop- Table 1.
ropyllithium (24) and the lithium salt of the titanium()
Because of the equilibrium possible between 10 and 23
complex 25 [Equation (5)]. However, the fatal flaw in this [depicted in Equation (4)], it became important to ascertain
proposal is that isopropyllithium is an extremely active li- which reactions reported in Table 1 are unambiguously at-
thium reagent that attacks ethers and is thereby destroyed, tributable to reagent 23 and which could equally be caused
with lithium alkoxide elimination, even at 25 °C.[ Under by reagent 10. To this end, titanium() isopropoxide, which
the reaction conditions used to prepare a mixture 10 and was essentially free of lithium isopropoxide (11) and hence
9]
1
1 for reaction with benzonitrile (15), according to of any 23, was generated according to Equation (3). Re-
Scheme 3, no isopropyllithium would have been expected agent 10 was then individually allowed to react with many
to survive.
of the same polar substrates, which had previously been
treated with reagent 23, and the results are listed in Table 2.
Through a comparison of the reaction products from in-
dividual substrates towards reagent 23 (Table 1) and to-
wards reagent 10 (Table 2), the following conclusions can
be reached. First of all, only reagent 23, not reagent 10,
can introduce an isopropyl group into any of the organic
(
5)
The remaining possibility, therefore, is that the ionic com- substrates, as it does with benzonitriles 15, 26 and 27 (ent-
plex 23 itself is the actual isopropylating agent for benzon- ries 1,2,3), (dichloromethyl)benzene (29, entry 5) and (tri-
itrile (15). In order to evaluate this hypothesis, a series of chloromethyl)benzene (30a, entry 6 in Table 1) [cf. Scheme 3
polar substrates, ranging from substituted benzonitriles and Equation (6) and (7)]. Secondly, with respect to the iso-
through benzylic and aryl halides to epoxides and finally propylation of benzonitriles by 23, it is most noteworthy
to aryl-conjugated acetylenes and olefins, were individually that some substituted benzonitriles, such as the 2-methoxy
treated with lithium complex 23, prepared according to (26, entry 2, Table 1) and 4-methoxy (27, entry 3) derivat-
Eur. J. Inorg. Chem. 2002, 3091Ϫ3096
3093

J. J. Eisch, J. N. Gitua
Yield (%)[b]
SHORT COMMUNICATION
Table 2. Reactions of the titanium() isopropoxide (10, free of LiOiPr) in THF with organic substrates
Entry
Substrate[a]
Products
1
2
Benzonitrile (15)
Benzyl phenyl ketone
Benzaldehyde
trans-Stilbene
meso-1,2-Dichloro-1,2-diphenylethane
1
1
84
11
5
(Dichloromethyl)benzene (29)
Dibenzyl
3
4
(trichloromethyl)benzene (30a)
Benzyl chloride (31)
1,1,2,2-Tetrachloro-1,2-diphenylethane
92
90
10
35
65
95
68
7
31
4
50
15
95
5
Dibenzyl
Toluene
Fluorene
5
9-Bromofluorene (32)
9,9Ј-Bifluorenyl
6
7
4-Bromoanisole (38)
trans-Stilbene oxide (34)
Anisole
trans-Stilbene (36)
Dibenzyl (40)
cis-Stilbene (35)
Dibenzyl (40)
trans-Stilbene (36)
Dibenzyl (40)
Polystyrene (42)
Ethylbenzene
8
9
Diphenylacetylene (37)
cis-Stilbene (35)
Styrene (38)
1
0
[
a]
Identical reaction conditions involving titanium() isopropoxide, prepared according to Equation (3), as those specified in footnote [a]
[
b]
1
of Table 1. The percent yields of products were obtained from the integrated H NMR spectra; recovered starting substrate ϭ 100%
Ϫ % of products.
ives underwent the isopropylation reaction readily,[5] but the
2,6-dimethyl derivative (28, entry 4) did not react at all. The
failure of 28 to react with 23 can readily be ascribed to
steric hindrance to the close approach of 23 to the CϵN
(
8)
group in 28 because of the flanking CH groups.
3
(
(
6)
7)
(9)
(
10)
Thirdly, in those cases where no isopropylation of the
organic substrate takes place, reagents 23 and 10 can effect
The final valuable conclusion deducible from these reduc-
monomolecular and bimolecular reductions, deoxygena- tions by reagents 10 or 23 concerns their underlying mech-
tions or dehalogenations to various degrees. Although not anism of reaction. First, that cis-stilbene (35) undergoes
without exception, the results given in Table 1 and 2 indic- extensive isomerization to trans-stilbene (36) in the course
ate that reagent 23 is a more active reductant than reagent of epimetallation to 39 is consistent with the formation of
10. Thus in the reduction of benzyl chloride (31) or of 9- the biradical intermediate 41 by single-electron transfer
bromofluorene (32) the monomolecular and bimolecular re- (SET). This intermediate can then either ring-close to 39 or
duction depicted in Equation (8) is complete in 12 h with reeliminate 23 to form the trans-isomer 36 (Scheme 4).[
10]
2
3 but requires 24 h with 10 (entries 7 and 8, Table 1, versus
Furthermore, that the cis- and trans-stilbene oxides (33
entries 4 and 5, Table 2). In another instance, the deoxy- and 34) undergo non-stereoselective deoxygenation[ to
genation of cis- or trans-stilbene oxide (33 or 34) proceeds give chiefly trans-stilbene (36) again strongly supports an
more cleanly and rapidly to the stilbenes 35 or 36 with 23 isomerizable radical ion intermediate (42), which can lead
than with 10 (entries 10 and 11, Table 1, versus entry 7, principally to the more stable trans-olefin 36 [Equa-
Table 2; Equation (9) and (10)]. But with other substrates, tion (11)]. Finally, that styrene undergoes polymerization
such as diphenylacetylene (37) and the stilbenes 35 and 36, much more rapidly than epimetallation with 23, compared
the extent of reduction with either 23 or 10 is not markedly with 10, further corroborates the superior SET donor char-
different. The behavior of 4-bromoanisole is anomalous in acter of 23 in forming the styrene radical-anion interme-
this regard, being much more readily reduced by 10 than diate, crucial in such polymerization. Compelling preced-
11]
by 23 (entry 6 in Table 2 versus entry 9 in Table 1).
ents for SET mechanisms for both olefin isomerization and
3094
Eur. J. Inorg. Chem. 2002, 3091Ϫ3096

Evidence for SET Processes in Transition-Metal Oxidative Additions
SHORT COMMUNICATION
Scheme 4
Scheme 5
conjugated olefin polymerization are available in the work Radical 46 accepts an isopropyl radical from the caged TiIII
of Swarc and co-workers on the ‘‘living polymerizations’’ radical to form 47. Simple dehydrohalogenation by LiOiPr
of diolefins by alkali metals.[
12]
leads to the final product 30.
In summary, a most unusual intramolecular oxidative ad-
dition of an ionic titanium() alkoxide (23), leading to a
complex of titanium(), probably 25, has been observed to
occur with a variety of reducible organic substrates. The
organic substrate undergoes either simple reduction or isop-
ropylating reduction via pathways most likely involving
SET processes.
(
11)
Conclusions
Experimental Section
In light of the foregoing unexpected isopropylations of
carbon centers and the nature and stereochemistry of many Instrumentation, Analysis and Starting Reagents: All reactions were
of the observed reductions, we conclude that the actual re- carried out under a positive pressure of anhydrous, oxygen-free ar-
agent in most of these reactions is dilithium tetraisopropoxy- gon. All solvents employed with organometallic compounds were
dried and distilled from a sodium metal-benzophenone ketyl mix-
titanate() (23) and not titanium() isopropoxide (10)
ture prior to use.[
13]
The IR spectra were recorded with a
alone, and that such processes involve SET pathways. The
mode of action of 23 as an isopropylating agent towards
benzonitrile (15) is proposed in Scheme 5, Part A. The
caged radical-anions formed by SET (43) can then undergo
an isopropyl-radical transfer to the sterically accessible ni-
trile carbon to form the final adduct 44. In Part B, (dichloro-
PerkinϪElmer instrument (model 457) and samples were measured
1
either as mineral oil mulls or as KBr films. The NMR spectra ( H
1
3
and C) were recorded with a Bruker spectrometer (model EM-
60) and tetramethylsilane (Me Si) was used as the internal stand-
ard. The chemical shifts reported are expressed on the δ scale in
parts per million (ppm) from the Me Si reference signal. The GC/
3
4
4
methyl)benzene (29) undergoes SET with 23 to form rad- MS measurements and analyses were performed with
ical-anion 45, which loses a Cl anion to form radical 46. HewlettϪPackard GC 5890/HewlettϪPackard 5970 mass-selective-
a
Eur. J. Inorg. Chem. 2002, 3091Ϫ3096
3095

J. J. Eisch, J. N. Gitua
SHORT COMMUNICATION
detector instrument. The gas chromatographic analyses were car-
ried out with a HewlettϪPackard instrument (model 5880) pro-
benzonitrile (15). The small amounts of diketone formed from
26 and 27 (entries 2 and 3, Table 1) were probably generated
in a similar manner.
vided with
a
2-m OV-101 packed column or with
a
[
6]
J. J. Eisch, F. A. Owuor, P. O. Otieno, Organometallics 2001,
HewlettϪPackard instrument (model 4890) having a 30 m SE-30
capillary column. Melting points were determined on a Thomas-
Hoover Unimelt capillary melting point apparatus and are uncor-
rected.
20, 4132Ϫ4134.
[7]
In reactions of benzonitrile with other titanium() derivatives,
such as TiCl , considerable amounts (30%) of benzyl phenyl
2
ketone were isolated: J. J. Eisch, X. Shi, unpublished studies.
[
8] [8a]
Titanium() chloride, for example, forms anionic complexes
Preparation of Titanium(II) Isopropoxide (10, Free of LiOiPr):
nBuLi (1.28 g, 12.5 mL, 1.6  solution in hexane, 20 mmol) was
added slowly at Ϫ78 °C to a stirred solution of titanium() chlor-
ide (1.89 g, 10 mmol) in THF (40 mL) under an argon atmosphere
and the mixture stirred for 30 minutes at this temperature. Then
the slow addition of isopropyl alcohol (1.20 g, 1.53 mL, 20 mmol)
was performed at the same low temperature. The resulting reaction
mixture was allowed to warm to 25 °C over 10 h to yield a dark
brown suspension, which was then cooled to Ϫ78 °C and a further
two equivalents of nBuLi (20 mmol) were slowly added at the same
temperature. The resulting dark brown suspension was then al-
lowed to warm to 25 °C over a 10 h period to yield a black solution
of titanium() isopropoxide (1.66 g, 100%) from which white LiCl
precipitated on standing.
2Ϫ
3Ϫ
of the types [TiCl
4
]
5
and [TiCl ] : G. W. A. Fowler, T. E.
Lester, R. A. Walton, J. Am. Chem. Soc. A 1968, 1081Ϫ1085.
[8b]
More recently characterized anionic titanium() complexes
include Na TiCl (D. J. Hinz, T. Dedecke, W. Urland, G.
2
4
Meyer, Z. Anorg. Allg. Chem. 1994, 620, 801Ϫ804) and Na
Ti Cl (D. J. Hinz, G. Meyer, T. Dedecke, W. Urland, Angew.
Chem. Int. Ed. Engl. 1995, 34, 71Ϫ73).
9]
2
-
3
8
[
P. D. Bartlett, S. Friedman, M. Stiles, J. Am. Chem. Soc. 1953,
5, 1771Ϫ1772: Isopropyllithium reacts with diethyl ether exo-
7
thermally at room temperature to form lithium ethoxide and
ethylene:
The excess iPrLi then adds to the ethylene to form isoamylli-
thium, which can be trapped with CO
the observed diisoamyl ketone:
2
to give, after hydrolysis,
Preparation of Titanium(II) Isopropoxide (23, Containing LiOiPr):
nBuLi (1.28 g, 12.5 mL, 1.6  solution in hexane, 20 mmol) was
added slowly at Ϫ78 °C to a stirred solution of titanium() isoprop-
oxide (2.84 g, 10 mmol) in THF (40 mL) under an argon atmo-
sphere and the mixture stirred for 2 h at this temperature. The re-
sulting light-brown reaction mixture was then allowed to warm to
[10]
Solutions of 23 and 10 in THF are paramagnetic as shown by
ESR spectroscopic measurement at room temperature. In fact,
solutions of 23 give a strong triplet signal, consistent with the
presence of two unpaired electrons. However, from the magni-
tude of the spin coupling, the two electrons are not on the same
titanium atom, and probably not even on adjacent titanium
centers. (Studies in progress with Professor D. C. Doetschman).
25 °C over 10 h to yield a dark brown-black solution of titanium()
isopropoxide (1.66 g, 100%).
Acknowledgments
This research has been conducted with the financial support of the
U.S. National Science Foundation, a Senior Scientist Award to
J.J.E. from the Alexander von Humboldt Stiftung of Bonn, Ger-
many, and a grant from the Solvay Corporation of Brussels,
Belgium. Furthermore, we are indebted to former group members,
Drs. Xian Shi and Sven Thiele, for valuable orienting experiments.
[11] One-step deoxygenations of epoxides with polar reagents such
as lithium diphenylphosphide lead stereospecifically to the ol-
efin with inverted configuration. Deoxygenations with SET re-
agents, such as nickel() complexes, occur stereoselectively to
favor the more stable olefin: J. J. Eisch, K. R. Im, J. Organomet.
Chem. 1977, 139, C45ϪC50.
12] [12a]
[
M. Swarc, Ions and Ion Pairs in Organic Reactions, Wiley,
New York, Vols. 1 and 2, 1972. [
12b]
M. Swarc, in Polynuclear
[
1]
J. J. Eisch, F. A. Owuor, P. O. Otieno, Organometallics 2001,
0, 4132Ϫ4134.
J. J. Eisch, J. Organomet. Chem. 2000, 617Ϫ618, 148Ϫ157.
J. J. Eisch, J. R. Alila, Organometallics 2000, 19, 1211Ϫ1213.
J. J. Eisch, J. N. Gitua, P. O. Otieno, X. Shi, J. Organomet.
Chem. 2001, 624, 229Ϫ238.
Aromatic Compounds (Ed.: L. B. Ebert), American Chemical
Society, Washington, D. C., 1988, pp. 13Ϫ37.
A detailed description for conducting organometallic reactions
in a safe and reproducible manner is given in: J. J. Eisch, Or-
ganometallic Syntheses, Vol. 2, Academic Press, New York,
1981, pp.1Ϫ84.
2
[
[
[
2]
3]
4]
[13]
[
5]
1
,3-Diketone 19 undoubtedly arose from the lithium isopro-
Received August 9, 2002
poxide-promoted addition of isopropyl phenyl ketone (18) to
[I02451]
3096
Eur. J. Inorg. Chem. 2002, 3091Ϫ3096