Titanium-catalyzed iminohydrazination of alkynes

Article abstract of DOI:10.1016/j.jorganchem.2005.03.025

Titanium pyrrolyl complexes Ti(NMe₂)₂(dap) ₂ (1), where dap is 2-(N,N-dimethylaminomethyl)pyrrolyl, and Ti(NMe₂)₃(bap) (3), where bap is 2,5-bis(N,N- dimethylaminomethyl)pyrrolyl, were found to be eff

Full text of DOI:10.1016/j.jorganchem.2005.03.025

Journal of Organometallic Chemistry 690 (2005) 5066–5077
www.elsevier.com/locate/jorganchem
Titanium-catalyzed iminohydrazination of alkynes
Sanjukta Banerjee, Yanhui Shi, Changsheng Cao, Aaron L. Odom *
Michigan State University, Department of Chemistry, East Lansing, MI 48824, United States
Received 5 February 2005; received in revised form 15 March 2005; accepted 15 March 2005
Available online 4 May 2005
Abstract
2 2 2 2 3
Titanium pyrrolyl complexes Ti(NMe ) (dap) (1), where dap is 2-(N,N-dimethylaminomethyl)pyrrolyl, and Ti(NMe ) (bap) (3),
where bap is 2,5-bis(N,N-dimethylaminomethyl)pyrrolyl, were found to be effective catalysts for the iminohydrazination of alkynes,
a new multicomponent coupling reaction involving an alkyne, hydrazine, and isonitrile. A brief study on the scope of the reaction
suggests that it is applicable to internal and terminal alkynes, alkyl and aryl isonitriles, and alkyl- and aryl-containing 1,1-disubsti-
tuted hydrazines. The best yields were obtained with terminal alkynes and alkyl isonitriles. The regioselectivity of the reactions is
quite sensitive to catalyst structure, and, in all cases, we were able to obtain one regioisomer of the iminohydrazination product
with either 1 or 3 as catalyst. The conformation of the products was probed by NMR spectroscopy and DFT calculations, which
suggest that the s-cis isomer of the hydrazone–enamine tautomer is the most favorable configuration. However, several configura-
tions are probably accessible in solution at room temperature. Reaction of 1 with 2 equivalents of H
tion of a dinuclear complex Ti (dap) (NNMe ) (NHNMe ) (4), where one dap ligand was removed protolytically. Examination of
2 2
NNMe results in the forma-
2
3
2 2
2
2 3
regioselectivities in iminohydrazination reactions using 4 and mono(dap) complex Ti(dap)(NMe ) (5) are consistent with these spe-
cies using the same catalytic cycle as 1. Consequently, the active species is likely a mono(dap) titanium complex. Current mechanistic
information is consistent with a hydrazido(2ꢀ) intermediate and a pathway reminiscent of the Bergman hydroamination mecha-
2 3 2 3 2 2 2
nism. Ti(NMe ) (bap) (3) and Ti (dap) (NNMe ) (NHNMe ) (4) were characterized by X-ray diffraction.
ꢀ
2005 Elsevier B.V. All rights reserved.
Keywords: Hydroamination; Hydrohydrazination; Iminoamination; Iminohydrazination; Titanium; Catalysis
1
. Introduction
Using titanium catalysts, alkynes can be hydrohyd-
razinated [4] (Scheme 2) with 1,1-disubstituted hydra-
zines, a process that generates hydrazones and indoles
(after Fischer cyclization) [5,6]. This procedure recently
has been elegantly expanded by Ackermann [7] and Bel-
ler [8] using alternative titanium catalysts to generate a
variety of indole derivatives.
Here we report that titanium complexes will also
catalyze the 3-component coupling of an isonitrile, 1,1-
disubstituted hydrazine, and alkyne. The alkyne is
formally iminohydrazinated during this process. The
products are tautomers of 3-imino-1-hydrazones, a,b-
unsaturated b-aminohydrazones, which are useful as
intermediates in organic synthesis and are derivatives
of the invaluable 1,3-diketone core [9]. In addition, these
compounds are related to 1,3-diimines, which are
The synthesis of complex and functional group-rich
organic products from simple building blocks [1] is an
important goal for transition metal catalysis and is aided
by multicomponent coupling reactions [2]. In this vein,
we recently reported that readily available titanium
complexes catalyze the 3-component coupling of an
amine, isonitrile, and alkyne in a new reaction that is
the formal iminoamination of an alkyne (Scheme 1).
[
1
3] The products of these reactions were tautomers of
,3-diimines, a,b-unsaturated b-iminoamines.
*
Corresponding author. Tel.: +1 5173557915x171; fax: +1
173531793.
E-mail address: odom@cem.msu.edu (A.L. Odom).
5
0
022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.03.025

S. Banerjee et al. / Journal of Organometallic Chemistry 690 (2005) 5066–5077
5067
NMe2
F5
NMe2
catalytic
N
NMe2
Ti NMe2
But
Ph
N
NMe2
NMe2
N
Ti
N
S
S
Ph
Me
PhNH2
N But
HN
Ti
NMe2
N
Me
N
Ph N
Me
Me
2
NHMe2
toluene, 100 C
˚
F5
C
Ti(dap) (NMe ) (1)
Ti(NMe ) (SC F )2(NHMe ) (2)
2 2 6 5 2
72%
2
2 2
Scheme 1. Example of iminoamination catalyzed by a titanium
pyrrolyl complex.
(
NMe2)3
Ti
NMe2
Me N
NMe2
2
N
NMe2
N
Ti
N
catalytic
Ph
N
NMe2
Me
NH2
2
N
N
N
Ti(bap)(NMe ) (3)
2 3
Me
1
Chart 1. Examples of titanium catalysts employed in these studies.
toluene, 100 C
˚
Ph
Me
For the current study, we also investigated the use of
the pyrrolyl ancillary ligand bis-2,5-(N,N-dimethylami-
nomethyl)pyrrolyl, bap. Addition of 1 equivalent of
Hbap to Ti(NMe ) results in the formation of Ti(N-
–
NH3
2
4
Ph
Me
N
Me ) (bap) (3). The two arms of the bap ligand are
2
3
equivalent by NMR spectroscopy in fluid solution. How-
ever, only one arm is coordinated in the solid-state
(
Fig. 1). In fact, the uncoordinated amine nitrogen is
˚
.1 A from titanium, and the equivalency of the two dim-
4
ethylamine donors in solution is likely due to fast exchage
66%
Scheme 2. Hydrohydrazination of an alkyne catalyzed by 1 and
Fischer cyclization.
processes. The tris(dimethylamido) Ti(NMe ) (bap) (3)
2
3
was advantageous for some substrates (vide infra). [11]
The anticipated route (Scheme 3) of the hydrohydraz-
ination was a modification of the Bergman mechanism
[12] for hydroamination [13,14] developed for zircono-
cene catalysis. In the presence of isonitrile, the azatitana-
cyclobutene [15] intermediate is trapped with C–C bond
formation to generate a new 5-membered metallacycle.
Protonolysis of the 4-membered metallacycle leads to
the hydrohydrazination product, and protonolysis of
the 5-membered metallacycle affords the iminohydrazin-
ation product.
common ligands for metal complexes [10]. However,
these unsymmetrical 1,3-iminohydrazones have not been
extensively utilized, perhaps due to the multistep proce-
dures that would ordinarily be required for their synthe-
sis. Using the iminohydrazination methodology, these
unsymmetrical compounds are available in a single,
multicomponent coupling step. In addition, some preli-
minary explorations into the mechanism of the imi-
nohydrazination reaction are detailed.
2
. Results and discussion
2
.1. Iminohydrazination results
The iminohydrazination reaction is a modification of
hydrohydrazination of alkynes [5–8] catalyzed by some
titanium complexes where a 1,1-disubstituted hydrazine
is added to an alkyne to generate a hydrazone (Scheme
2). In a previous study, we developed two catalysts for
alkyne hydrohydrazination, a titanium pyrrolyl complex
Ti(NMe ) (dap) (1), where dap is 2-(N,N-dimethylami-
2
2
2
nomethyl)pyrrolyl, and thiolate-containing Ti(NMe ) -
2
2
Fig. 1. Synthesis and solid-state structure of Ti(bap)(NMe ) (3) from
2
3
(
SC F ) (NHMe ) (2) (Chart 1).
5 2
X-ray diffraction.
6
2

5068
S. Banerjee et al. / Journal of Organometallic Chemistry 690 (2005) 5066–5077
R2N
N
NHR3
side reaction with some substrates. However, the hydraz-
ones are readily removed from the iminohydrazination
products by column chromatography or distillation.
Reactions with 1,1-diphenylhydrazine resulted in quite
low yields of multicomponent product, and the major
product observed was diphenylamine. While reactions
with 2,6-xylyl isonitrile were successful, yields were gen-
erally low with this substrate. Attempts to use acetylene
as the alkyne, which was very effective in our initial
hydrohydrazination studies, did not result in multicom-
ponent coupling products with 1 as catalyst.
R1
R2
NR2
N
iminohydrazination
H2NNR2
[
Ti]
R N
R1
2
N
R2
1
R
hydrohydrazination
R2
H2NNR2
R2N
R1
R N
R1
R2
2
N
N
R2
[
Ti]
[
Ti]
N
R3
2
1
.2. Studies on the conformation and tautomers of
,3-iminohydrazones
C
R3
N
Scheme 3. Titanium-catalyzed hydrohydrazination versus imino-
hydrazination.
In all of the reactions in Table 1, only one isomer is
observed by NMR. (However, see Section 2.6 for some
discussion of regioselectivity versus catalyst structure.)
From previous studies on related tautomers and con-
formers [16,9c], we assumed that the conformers shown
in Table 1 would be favored. The s-cis isomers are be-
lieved to be more favorable in most cases due to poten-
tial hydrogen bonding between the two nitrogens. From
our NMR studies, the favored tautomeric form is the
hydrazone–enamine.
Computational studies on the product of Entry 1 in
Table 1 were carried out to probe the energy differences
between some of the conformers and in an attempt to
confirm the s-cis conformer as the most stable species.
To insure that the sterics of the molecule were accurately
depicted, the entire molecule without truncation was
used in the study. Four of the expected isomers were
minimized (s-cis amine, s-trans amine, s-cis imine, and
s-trans imine) with DFT(B3LYP) using the 6-
Some results of the iminohydrazination study using 1
and 3 as catalysts are shown in Table 1. The reactions
utilized a variety of terminal and internal alkynes, alkyl
and aryl hydrazines, and alkyl and aryl isonitriles to
demonstrate the scope of the catalysis. The purified
yields in this fairly broad but short study varied from
1
2% to 73%.
In our initial studies on hydrohydrazination [5], the
thiolate-based catalyst 2 was quite efficient for many dif-
ferent types of substrates, often exceeding the pyrrolyl-
based catalyst 1 in activity for certain combinations.
However, 2 was ineffective for most substrate combina-
tions in iminohydrazination, often providing no ob-
served products. The one combination for which 2 was
effective was for that shown in Entry 5 of Table 1, which
used the quite reactive phenylacetylene as substrate.
However, the reaction also showed a significant amount
of hydrohydrazination product making it less desirable
than 3 for the same reaction. Some activity was obser-
ved with the substrates in Entry 1 involving 1-hexyne.
However, the major product was one having a mass con-
sistent with a 4-component coupling involving 2 equiva-
lents of tert-butylisonitrile, 1 equivalent of 1-hexyne,
and 1 equivalent of 1,1-dimethylhydrazine. The oily
product seems unstable to both distillation and column
chromatography; consequently, its structure is currently
unknown.
3
1++G** basis set and local minima were found for
each. The minimized conformation and calculated en-
ergy for each isomer are shown in Fig. 2.
Consequently, the experimental and computational
studies suggest that the s-cis amine isomer is preferred.
While the accuracy of the energy differences calculated
are unknown, the ꢁ2 kcal/mol gap, assuming Arrhenius
behavior and no entropy difference between the two
molecules, would result in a solution that was ꢁ97% s-
cis amine. As a result, this magnitude of gap, though
small, is consistent with the s-cis imine being the only
conformer observed by NMR.
Some problems observed with amine substrates were
not observed with hydrazines. For example, with amine
substrates the carbon adjacent to the isonitrile group
was required to be quaternized for effective catalysis.
2.3. Possible 1,2-insertion mechanism
[
3] With hydrazines, substrates such as cyclohexylisonit-
An alternative mechanism to the one shown in
Scheme 1 is certainly plausible. The reaction could pro-
ceed through a route involving 1,2-insertion of the al-
kyne into a hydrazido(1ꢀ) intermediate (Scheme 4), a
pathway extensively studied by Marks and coworkers
[17]. The Marks hydroamination mechanism likely is
rile worked quite well (Entry 2, Table 1). The major side
reaction observed with amines was the production of
formamidine by two-component coupling of the amine
and isonitrile; we did not observe the analogous reaction
with hydrazines. Hydrohydrazination is observed as a

S. Banerjee et al. / Journal of Organometallic Chemistry 690 (2005) 5066–5077
5069
Table 1
Examples of alkyne iminohydrazination
R3
5
R HN
R3
R4
N
R4
N
R1
R2
H N
N
C N R5
2
R1
R2
1
R , R
2
3
R , R
4
5
a
Entry
R
Conditions
product (% yield)
NHBut
n
Bu , H
t
1
Me, Me
Bu
A,16 h
Me N
N
2
(63)
Bun
n
Bu , H
b
HN
2
3
4
5
Me, Me
Cy
A, 16 h
B, 43 h
A, 16 h
C, 16 h
A, 16 h
(73)
Me N
N
2
Bun
c
HN
Me, Ph
Me, Me
Ph, Me
Me, Me
Me, Me
Ar
(14)
Me N
N
2
Me
Ph
NHBut
Ph(Me)N
N
n
Bu , H
t
Bu
(27)
Bun
NHBut
Me N
N
t
2
H, Ph
Bu
(43)
Ph
n
Bu , H
c
HN
6
Ar
(12)
Me N
N
2
Bun
a
A is 10 mol% 1 in toluene at 100 ꢁC, B is 10 mol% 1 in toluene at 130 ꢁC, C is 10 mol% 3 in toluene at 100 ꢁC.
Cy is cyclohexyl.
b
c
Ar = 2,6-dimethylphenyl.
operative for some Group-4 [18], lanthanide [19], and
A reaction under the same conditions as those used
in Entry 1 of Table 1 with trimethylhydrazine in
place of 1,1-dimethylhydrazine was carried out, which
resulted in no observed reaction (Scheme 5) when mon-
itored by GC/FID. The inactivity of trimethylhydr-
azine is inconsistent with the 1,2-insertion mechanism
shown in Scheme 4, which only requires access to
hydrazido(1ꢀ) intermediates. This result suggests that
Group-3 hydroamination catalysts [20]. If the isonitrile
traps a resulting vinyl complex due to 1,1-insertion in
our system, the same iminohydrazination product would
result. For this mechanism, only hydrazido(1ꢀ) interme-
diates are required and reactions with trimethylhydr-
azine would be expected to give products similar to
those shown in Table 1.

5070
S. Banerjee et al. / Journal of Organometallic Chemistry 690 (2005) 5066–5077
Bun
H
Me
Me
Me
1
0 mol %1
00 C, 16h
No Reaction
HN
N
1
˚
C N But
Scheme 5. Attempted reaction of trimethylhydrazine, 1-hexyne, and
tert-butyl isonitrile with added 1.
about the route of the catalysis. Treatment of 1 with
1
,1-dimethylhydrazine results in the generation of a
2
1
new dinuclear complex Ti (dap) (l :g ,g -NNMe )
(
2
3
2
2
1
l :g -NHNMe ) (4), which has two bridging hydraz-
1 2
ido(2ꢀ) ligands and where one dap has been protolyti-
cally replaced with a hydrazido(1ꢀ). The synthesis and
structure from X-ray diffraction are shown in Fig. 3;
in that figure, the a-nitrogen for the hydrazido(1ꢀ) li-
gand is labeled N(11) and is attached to Ti(2). From
the isolated dinuclear complex, it is obvious that at least
one of the dap ligands is protolytically labile in the pres-
ence of 1,1-dimethylhydrazine. However, the active spe-
cies probably does contain at least one dap ligand
considering Ti(NMe ) is not a catalyst for hydrohyd-
Fig. 2. Minimized conformations and energies of the product in Entry
of Table 1 by DFT. The energies listed are relative to the s-cis amine
isomer, which is defined as 0 kcal/mol.
1
2
4
razination or iminohydrazination under any conditions
we have found.
t
Bu HN
Me NN
In order to determine if the complex 4 is competent
to be involved in the catalytic cycle, kinetic experi-
ments were attempted using 1 and 4 as catalysts. How-
ever, the reaction is apparently not suitable for a
detailed kinetic study, probably due to somewhat low
yields, and the results were highly variable even using
2
Bun
NH
Ti]
Me N
Bun
2
[
H NNMe
2
2
H
1
as catalyst. Values for rate constants had very large
Bun
Bun
errors. Consequently, we resorted to the use of a reac-
tion that provides a mixture of regioisomers (see
H
HN
Me N
HN
Me N
2
2
H
NBut
[Ti]
[
Ti]
C
N
But
Scheme 4. Possible 1,2-insertion mechanism for iminohydrazination.
hydrazido(2ꢀ) intermediates are a requirement for the
catalysis.
2
.4. Reactions between Ti(NMe ) (dap) (1) and
2 2 2
1
,1-dimethylhydrazine
The stoichiometric reaction of 1 with hydrazine was
carried out in an attempt to see what may be gleaned
Fig. 3. Synthesis and structure from X-ray diffraction of
1
2
1
2 3 2 2 1 2
Ti (dap) (l :g ,g -NNMe )(l :g -NHNMe ) (4).

S. Banerjee et al. / Journal of Organometallic Chemistry 690 (2005) 5066–5077
5071
NHR2
Section 2.6). With 1 as catalyst, the iminohydrazination
of phenylacetylene provides a mixture of regioisomers
along with small amounts of hydrohydrazination prod-
ucts. This catalysis was run six times, and the crude
GC/FID ratios were obtained. The ratio of iminohyd-
razination products was found to be 0.453 ± 0.177,
where the error is at the 99% confidence level. The ra-
tio of hydrohydrazination products observed was
Me N
N
2
NMe2
N
R1
R1
[
Ti]
NH
H2NNMe2
N
Me
NMe2
2
H
0
.443 ± 0.339. If the dinuclear complex gives catalysis
R2
N
Me2
N
resulting in the same ratios within error, this is reason-
ably good evidence for its involvement during catalyses
involving 1. The ratio found for dinuclear complex 4
was 0.383 for iminohydrazination and 0.172 for hydro-
hydrazination products, which is consistent with its
involvement when 1 is used.
N
Me N
R1
2
Ti
N
N
N
HN
[Ti]
R1
NMe2
NMe2
Me2N
Me N
2
N
R1
Considering the apparent protolytic lability of one
dap in 1, we generated and isolated the mono(dap) com-
plex Ti(dap)(NMe2) (5) by reaction of Lidap with
[Ti]
HN
C
3
N
ClTi(NMe ) [21]. Attempts to synthesize 5 by addition
2
N
3
R2
R2
of one equivalent of Hdap to Ti(NMe2)4 provided
mostly the bis(dap) complex 1. The mono(dap) com-
pound 5 appears to be comparable in catalytic activity
to 1. It provided a comparable yield when used instead
of 1 for the reaction shown in Entry 1 of Table 1. In
addition, its regioisomeric ratio for the reaction involv-
ing phenylacetylene, 1,1-dimethylhydrazine, and tert-
butylisonitrile was 0.478 for iminohydrazination
products and 0.238 for hydrohydrazination products,
the same within error as the ratios for 1. Consequently,
our current evidence is consistent with an active species
only bearing one dap ligand.
Scheme 6. Working model for iminohydrazination catalyzed by 1.
Ti] = Ti(dap).
[
2
.6. Some experimental observations on regioselectivities
The multicomponent coupling reaction between
tert-butylisonitrile, phenylacetylene, and 1,1-dimethylhy-
drazine using 1 as catalyst results in a mixture of
hydrohydrazination and iminohydrazination due to
competitive protonolysis and 1,1-insertion (Scheme 7).
In addition, both regioisomers are observed for both of
the two product types. As a result, the reaction provides
the opportunity to compare hydrohydrazination and
iminohydrazination regioselectivity in a single system.
For the 3-component coupling reaction, the isomer
having the phenyl group in the 2-position of the 1,3-hyd-
razonylimine (same product as that shown in Entry 5
of Table 1) is favored. The reaction was run six times
with 1 as catalyst. The ratio of amounts of 3-component
coupling products was found to be 0.453 ± 0.117 (99%
confidence level, m = 5). The range for the ratio of
regioisomers in the reactions run under the same
conditions was fairly large from 0.351 to 0.510. For the
2
.5. A working model for the catalytic cycle
From the information known about the mechanism
thus far, one can postulate the catalytic cycle shown in
Scheme 6. Here we assume based on the evidence
above that a hydrazido(2ꢀ) intermediate is involved
in a similar capacity as in the Bergman mechanism
for hydroamination [12]. Considering the mild condi-
tions under which 4 is formed relative to the catalytic
conditions and catalysis results using 5, it is likely that
the active species has only one dap ligand. The dinu-
clear complex 4 has 6-coordinate and 7-coordinate
titanium centers making it unlikely to be involved di-
rectly in the catalytic cycle. Consequently, we assume
that it is an intermediate between 1 and the active spe-
cies, which is likely a lower coordinate, monomeric
titanium complex with one dap ligand. When possible,
the b-nitrogen of hydrazido complexes is often acting
as a donor towards titanium, e.g., complex 4 above,
and is depicted as doing so below. Additional experi-
mental evidence concerning the mechanism of imino-
amination and iminohydrazination will be sought in
future investigations [22].
NMe2
Me
t
Bu HN
N
N
Ph
C
H
Me N
2
A'
B'
A
Ph
catalytic 1
Ph
N
But
t
Me2N
H
Bu HN
N
N
Me N
B
2
2
H NNMe2
Ph
Ph
[
A]
B]
[A']
[B']
0
.453± 0.117
0.442 ± 0.339
[
Scheme 7. Results of iminohydrazination of phenylacetylene when
catalyzed by 1.

5072
S. Banerjee et al. / Journal of Organometallic Chemistry 690 (2005) 5066–5077
same experiments, the ratio of hydrohydrazination
products was 0.442 ± 0.339 with a range from 0.236 to
strate. Initial indications, albeit based on circumstantial
evidence, are that the mechanism involves terminal
hydrazido(2ꢀ) complexes that undergo [2 + 2] cycload-
dition with the alkyne. In addition, current evidence sug-
gests that the active species is a mono(dap) complex,
which maybe formed under relatively mild conditions
when Ti(dap) (NMe ) is reacted with H NNMe .
0
.750. While the errors are large on these ratios, it
should be kept in mind that the values are quite sensitive
to catalyst structure. For example, the ratios of regioi-
somers when using the closely related catalyst Ti
(
bap)(NMe ) (3) for the same reaction are <0.01 for
2 3
2
2 2
2
2
both the hydrohydrazination and iminohydrazination
products, only one regioisomer is observed for each
product.
Admittedly, the errors are quite large, but the mean
values are remarkably close. This suggests that, to a first
approximation, the ratio of the different isomers is
nearly the same for the hydrohydrazination and imi-
nohydrazination reactions. The similar regioselectivities
are consistent with an important regiochemical event
being associated with a step prior to protonolysis or
As can be seen from the content of Table 1, the reac-
tions are significantly enhanced by having terminal alky-
nes. Many attempted substrate combinations were quite
sluggish due to the relatively low activity of these initial
catalysts. It is hoped that additional studies will lead to
improved catalyst performance and enable the use of
internal alkynes on a routine basis. However, these re-
sults suggest that iminohydrazination is an effective
methodology for 3-imino-1-hydrazones with some sub-
strates even using these initially discovered catalyst
architectures.
1
,1-insertion (Scheme 3), e.g., [2 + 2] cycloaddition
and/or alkyne coordination. This is in agreement with
a recent assertion from the Beller group that titanium
hydroamination regioselectivities correlate with calcu-
lated relative energies associated with alkyne coordina-
tion regioselectivity [23]. However, the experimental
protonolysis and 1,1-insertion regioselectivities may or
may not be identical, since the gross regioselectivity-
determining events are the same (the [2 + 2] cycloaddi-
tion) but other factors still contribute to the final value.
In other words, the equilibrium between the two azame-
tallacycles contributes to the regioselectivities in both
reactions, but the relative trapping rates of the two
metallacycles may be slightly different with protons
and isonitriles.
Switching the ancillary ligands on titanium can favor-
ably affect the regioselectivities. Using 3 as catalyst
provides only one regioisomer; however, both hydro-
hydrazination and iminohydrazination products are still
observed. In fact, they are observed in a similar ratio as
when using catalyst 1, suggesting that the regioselectiv-
ity of the [2 + 2] cycloaddition was dramatically effected,
but the relative rate of protonation versus 1,1-insertion
was not greatly perturbed by the change in ancillary li-
gand in this particular case.
4. Experimental
4.1. General considerations
All manipulations of air sensitive compounds were
carried out in an MBraun drybox under a purified nitro-
gen atmosphere. Anhydrous ether was purchased from
Columbus Chemical Industries Inc. and freshly distilled
from purple sodium benzophenone ketyl. Toluene was
purchased from Spectrum Chemical Mfg. Corp. and
purified by refluxing over molten sodium under nitrogen
for at least 2 days. Pentane (Spectrum Chemical Mfg.
Corp.), tetrahydrofuran (JADE Scientific), and benzene
(EM Science) were distilled from purple sodium benzo-
phenone ketyl. Dichloromethane (EM Science) and ace-
tonitrile (Spectrum Chemical) were distilled from
calcium hydride. Hydrazines were purchased from Al-
drich Chemical Company and dried by distillation from
KOH under dry nitrogen. Alkynes were distilled under
dry nitrogen. Ti(NMe ) [24] and TiCl(NMe ) [21] were
2
4
2 3
prepared using the literature procedures. The Hdap li-
gand was prepared as described in the literature
[
25,26]. Lidap was prepared by addition of 1.1 equiva-
n
lents of LiBu to a toluene solution of Hdap; the Lidap
was collected by filtration and washed with pentane to
afford the colorless product. Hbap was prepared using
the literature procedure [26]. tert-Butyl isonitrile [27]
and 2,6-xylyl isonitrile [28] were prepared from the
amine using published methods. Cyclohexyl isonitrile
was purchased from Aldrich Chemical Company and
distilled under dry nitrogen prior to use. Deuterated sol-
vents were dried over purple sodium benzophenone ke-
tyl (C D ) or phosphoric anhydride (CDCl ) and
3
. Concluding remarks
Titanium pyrrolyl complexes have allowed the exam-
ination of a new reaction, iminohydrazination of an al-
kyne. The reaction seems to have a fairly large substrate
scope. Attempts to use trimethylhydrazine in place of
1
,1-dimethylhydrazine, which would prevent formation
of the terminal hydrazido(2ꢀ) ligand, resulted in no
multicomponent coupling product being observed. If a
1
6
6
3
1
13
,2-insertion pathway (cf. the Marks Hydroamination
mechanism and Scheme 4) was accessible, one might ex-
pect that some product would be formed using this sub-
distilled under nitrogen. H and C spectra were re-
1
corded on Inova-300 or VXR-500 spectrometers. H
1
3
and C assignments were confirmed when necessary

S. Banerjee et al. / Journal of Organometallic Chemistry 690 (2005) 5066–5077
13
5073
1
1
1
with the use of two-dimensional H– H and C– H cor-
relation NMR experiments. All spectra were referenced
Under an atmosphere of dry nitrogen, a threaded
pressure tube was loaded with toluene (6 mL), Ti-
(dap) (NMe ) (0.457 g, 1.20 mmol), 1,1-dimethylhydra-
1
13
internally to residual protiosolvent ( H) or solvent ( C)
resonances. Many common coupling constants are not
listed. Chemical shifts are quoted in ppm and coupling
constants in Hz.
2
2 2
zine (910 lL, 12 mmol), 1-hexyne (1399 lL, 12.00
mmol), and cyclohexyl isocyanide (1790 lL, 14.4 mmol).
The tube was sealed with a Teflon cap and heated
at 100 ꢁC for 16 h. The solvent was removed under
vacuum. The product was isolated by distillation under
vacuum (ꢁ110 ꢁC, 0.65 Torr) in 73% yield (2.205 g,
4
4
.2. Synthesisandcharacterizationofcompoundsin Table1
.2.1. Entry 1 of Table 1
1
.785 mmol) as brown oil. H NMR (300 MHz, CDCl ):
8
3
e
d = 9.61 (br s, 1H, NH.6 ), 6.74 (d, 1H, J = 8.1 Hz,
HH
g
f
CH.6 ), 4.61 (d, 1H, J = 8.1 Hz, CH.6 ), 2.68 (m,
HH
i
j
8
H, CH and CH ), 2.09–1.93 (m, 11H, a, b, c, d),
3
2
k l
CbMea
3
1.73 (m, 2H, CH ), 1.57 (m, 2H, CH ), 1.14 (t, 3H,
2 2
m
13 1
Hc
N
JHH = 7.1 Hz, CH ).
C{ H} NMR (300 MHz,
Me2gN N
3
d
h
f
g
CDCl ): d = 171.9 (C N), 142.5 (C H), 89.9 (C H),
3
f
e
j
56.0 (C H
i
), 49.8 (C H
k
), 47.9 (C H
l
), 34.8 (C H
h
j
2
3
2
2
),
1.5 (C H ), 26.2 (C NH), 24.9 (C H ), 23.0 (C H ),
i
m
a
b
c
3
1
3
2
2
d
3.9 (C H ). Elemental analysis; experimental (Calc.),
2
k
C: 71.71 (71.71). H: 11.96 (11.55). N: 16.80 (16.73).
+
MS (EI) m/z = 251(M ).
Under an atmosphere of dry nitrogen, a threaded
pressure tube was loaded with toluene (6 mL), Ti
4.2.3. Entry 3 of Table 1
(
zine
dap) (NMe ) (0.458 g, 1.20 mmol), 1,1-dimethylhydra-
2 2 2
(910 lL,
12 mmol),
1-hexyne
(1399 lL,
1
2.00 mmol), and tert-butyl isocyanide (1355 lL,
e
1
2.00 mmol). The tube was sealed with a Teflon cap
d
b
c
and heated at 100 ꢁC for 16 h. The solvent was removed
under vacuum. The product was isolated by distillation
Hf
N
N
a
j
Me N
g
2
under vacuum (ꢁ65 ꢁC, 0.65 Torr) in 63% yield (1.702 g,
h
1
.564 mmol) as red oil. H NMR (300 MHz, CDCl ):
i
l
k
7
Meo
3
c
d = 9.82 (br s, 1H, NH ), 6.88 (t, 1H, J = 6.2 Hz,
HH
d
CH ), 4.68 (d, 1H, J = 8.1 Hz, CH ), 2.71 (m, 8H,
e
HH
n
m
g
3
i
2
k
3
j
2
h
2
CH and CH ), 1.77 (m, 2H, CH ), 1.64 (m, 2H,
g
CH ), 1.52 (s, 9H, CH ), 1.17 (t, 3H, J = 8.0 Hz,
3
HH
13
1
Under an atmosphere of dry nitrogen, a threaded
pressure tube was loaded with toluene (4.5 mL), Ti
dap) (NMe ) (0.344 g, 0.900 mmol), 1,1-dimethylhy-
drazine (1024 lL, 13.50 mmol), 1-phenylpropyne
1078 lL, 9 mmol), and xylyl isocyanide (1.769 g,
3.50 mmol). The tube was sealed with a Teflon cap
CH ). C{ H} NMR (300 MHz, CDCl ): d = 171.5
3
f
NNC ), 139.6 (C H), 89.5 (C H), 51.5 (C H ), 48.9
d
e
g
(
(
3
h
i
j
C H ), 47.5 (C H ), 31.2 (C H ), 30.4 (C (CH ) ),
b
(
2
2 2
2
2
2
3 3
k
a
2
mental (Calc.), C: 69.41 (69.33). H: 12.35 (12.00). N:
3.1 (C H ), 13.9 (C H ). Elemental analysis; Experi-
3 3
(
1
+
8.85 (18.67). MS (EI) m/z = 225(M ).
1
and heated at 130 ꢁC for 43 h. The volatiles were re-
moved under vacuum. The product was then isolated
by column chromatography on Florisil. The impurities
were removed as the first fraction using 1:1 pen-
tane:ethyl acetate mixture. The product was then iso-
lated with pure ethyl acetate in 15% yield (0.401 g,
4
.2.2. Entry 2 of Table 1
1
d
c
1.31 mmol) as a dark brown viscous oil. H NMR
f
(300 MHz, CDCl
): d = 11.31 (br s, 1H, NH ), 7.35–
6.69 (m, 8H, Ph, d, e, l, m, n), 6.82 (d, 1H, JHH = 7.3 Hz,
3
a
f
b
He
N
g
CH ), 2.66 (s, 6H, CH ), 2.43 (s, 6H, CH ), 2.23 (s, 3H,
j
a
N
3
3
i
Me N
o
13
1
2
CH ). C{ H} NMR (300 MHz, CDCl ): d = 166.3
3
3
h
k
g
i
g
C N), 142.7 (C H), 142.0–118.0 (Ph), 108.3 (H CC ),
h
(
j
3
j
o
a
48.2 (N(C H ) ), 19.5 (C H ), 17.9 (C H ). Elemental
3 2 3 3
l
analysis; experimental (Calc.), C: 77.88 (78.17). H: 8.33
+
(8.14). N: 13.49 (13.68). MS (EI) m/z = 307(M ).
m

5074
S. Banerjee et al. / Journal of Organometallic Chemistry 690 (2005) 5066–5077
4
.2.4. Entry 4 of Table 1
(300 MHz, CDCl ): d = 9.03 (br d, 1H, J = 13.0 Hz,
3 HH
c f
NH ), 7.65 (s, 1H, CH ), 7.40–7.15 (m, 5H, Ph, i, j, k),
d
g
3
6
.89 (d, 1H, J = 2.3 Hz, CH ), 2.83 (s, 6H, CH ),
j
HH
g
k
13
1
i
CbMea
1.36 (s, 9H, CH ). C{ H} NMR (300 MHz, CDCl
3
):
3
3
f
d
Hc
N
h
d = 143.0 (C N), 142.0 (Ph, h), 136.0 (C H), 128.5 (Ph,
i), 125.0 (Ph, j), 124.0 (Ph, k), 102.9 (C Ph), 50.9
e
N N
d
Meg
b
g
a
e
(C Me ,), 42.0 (C H ), 30.0 (C H ). Elemental analysis;
3 3 3
f
l
experimental (Calc.), C: 73.58 (73.47). H: 9.26 (9.39). N:
+
17.05 (17.14). MS (EI) m/z = 245(M ).
m
n
o
4
.2.6. Entry 6 of Table 1
Under an atmosphere of dry nitrogen, a threaded
pressure tube was loaded with toluene (4.5 mL), Ti
dap) (NMe ) (0.344 g, 0.900 mmol), 1-methyl-1-phen-
d
c
Me
(
2
2 2
a
b
ylhydrazine (1059 lL, 9.00 mmol), 1-hexyne (1119 lL,
Hf
Mee
N
j
9
9
.00 mmol), and tert-butyl isocyanide (1018 lL,
.00 mmol). The tube was sealed with a Teflon cap
Me N N
g
2
i
l
h
k
and heated at 100 ꢁC for 13 h. The solvent was removed
under vacuum. The product was isolated by distillation
m
under vacuum (ꢁ110 ꢁC, 0.65 Torr) in 27% yield
n
1
0.693 g, 2.414 mmol) as dark brown oil. H NMR
(
c
(
300 MHz, CDCl ): d = 9.69 (br s, 1H, NH ), 7.27–
3
d
.83 (m, 5H, Ph, i, j, k), 6.93 (m, 1H, CH ), 4.57 (d,
Under an atmosphere of dry nitrogen, a threaded
pressure tube was loaded with toluene (6 mL), Ti
(dap) (NMe ) (0.432 g, 1.20 mmol), 1,1-dimethylhydra-
6
1
2
2
e
g
H, JHH = 8.1 Hz, CH ), 3.11 (s, 3H, CH ), 2.36 (t,
H, JHH = 7.7 Hz, CH ), 1.50 (m, 2H, CH ), 1.39 (m,
H, CH ), 1.29 (s, 9H, CH ), 0.89 (t, 3H, J = 7.2 Hz,
3
m
l
2
2 2
2
2
n
2
13
g
3
zine (910 lL, 12 mmol), 1-hexyne (1399 lL, 12 mmol),
and xylyl isocyanide (1.573 g, 12 mmol). The tube was
sealed with a Teflon cap and heated at 100 C for 16 h.
The volatiles were removed under vacuum. The product
was then isolated by column chromatography on Flori-
sil. The impurities were removed as the first fraction
using 1:1 dichloromethane:ethyl acetate mixture. The
product was then isolated with ethyl acetate as the elu-
HH
o
3
1
CH ). C{ H} NMR (300 MHz, CDCl ): d = 176.3
3
f
C N), 152.2 (C H), 140.9 (C N), 128.5 (C N), 118.0
d
h
i
(
(
(
j
k
e
g
C H), 113.9 (C H), 89.1 (C H), 51.0 (C H ), 42.8
3
l
m
n
b
C H ), 32.0 (C H ), 30.3 (C H ), 30.1 (C (CH ) ),
2 2 2 3 3
o
a
22.8 (C H ), 13.8 (C H ). Elemental analysis; Experi-
3 3
mental (Calc.), C: 75.29 (75.26). H: 10.49 (10.10). N:
+
4.72 (14.63). MS (EI) m/z = 287(M ).
1
ent in 12% yield (0.401 g, 1.47 mmol) as a viscous oil.
1
H NMR (300 MHz, CDCl ): d = 10.89 (br s, 1H,
3
f
NH ), 7.15–6.85 (m, 3H, Ph, c, d), 6.78 (d, 2H,
4
.2.5. Entry 5 of Table 1
g
JHH = 7.8 Hz, CH ), 4.62 (d, 1H, J = 8.0 Hz, CH ),
h
HH
j
k
e
2
.58 (m, 8H, CH and CH ), 2.38 (s, 6H, CH ), 1.59
3
3 3
l m
b
a
C Me
3
Hc
(m, 2H, CH ), 1.41 (m, 2H, CH ), 0.99 (t, 3H,
N
2
2
n
3
13
1
C{ H} NMR (300 MHz,
Me2gN N
d
e
JHH = 7.3 Hz, CH ).
i
g
CDCl ): d = 170.4 (C N), 143.1 (C H), 141.8–117.9
3
f
h
h
j
k
(
(
Ph), 92.0 (C H), 48.8 (C H ), 46.6 (C H ), 31.4
3 2
i
l
C H ), 23.0 (C H ), 19.3 (C H ), 14.0 (C H ). High res-
e
m
n
2
3
2
3
j
k
olution MS (EI) m/z = 273.2200, calc. = 273.2205.
.3. SynthesisandcharacterizationofTi(bap)(NMe ) (3)
4
2
3
Under an atmosphere of dry nitrogen, a threaded
pressure tube was loaded with toluene (4.9 mL), Ti
bap)(NMe2)3 (0.353 g, 0.980 mmol), 1,1-dimethylhy-
drazine (743 lL, 9.80 mmol), phenylacetylene
1075 lL, 9.80 mmol), and tert-butyl isocyanide
1107 lL, 9.80 mmol). The tube was sealed with a Teflon
(
(NMea2)3
Ti
Me2bN
(
(
c
NMeb2
N
e
e
c
d
cap and heated at 100 ꢁC for 16 h. The solvent was re-
moved under vacuum. The product was isolated by dis-
tillation under vacuum (ꢁ125 ꢁC, 0.65 Torr) in 43%
d
Under an atmosphere of dry nitrogen, a solution of
Ti(NMe2)4 (2.00 g, 8.90 mmol) in ether (20 mL) was
1
yield (1.030 g, 4.20 mmol) as a red oil. H NMR

S. Banerjee et al. / Journal of Organometallic Chemistry 690 (2005) 5066–5077
5075
frozen in a liquid nitrogen cooled cold well. The solution
was allowed to warm enough to be stirred. Then, a cold
solution of Hbap (1.610 g, 8.90 mmol) in 10 mL ether
was added to the above solution dropwise over a period
of 20 min. It was allowed to warm up to room temper-
ature and stir overnight. The volatiles were removed un-
der vacuum. The solid was purified by crystallization as
C D ): d = 137.2 (pyrrole, u), 136.1 (pyrrole, o), 133.5
6 6
(pyrrole, g), 130.6 (pyrrole, x or r), 129.5 (pyrrole, h),
108.0 (pyrrole, j), 107.3 (pyrrole, q or w), 106.7 (pyrrole,
q or w), 102.1 (pyrrole, p or v), 101.8 (pyrrole, i), 101.4
(pyrrole, p or v), 65.5 (CH , n), 63.0 (CH , t), 62.9 (CH ,
2
2
2
f), 54.4 (CH , a or b or k or l), 54.3 (CH , a or b or k or
3
3
l), 51.0 (CH , e), 50.6 (CH , a or b or k or l), 50.3 (CH ,
3
3
3
orange–red crystals from pentane (2.950 g, 8.20 mmol)
1
a or b or k or l), 49.8 (CH , m or s), 49.4 (CH , m or s).
3 3
in 92% yield. H NMR (300 MHz, CDCl ): d = 6.34 (s,
Elemental analysis; experimental (Calc.), C: 50.93
(50.64). H: 8.48 (8.12). N: 26.07 (26.25).
3
d
c
2H, CH ), 3.48 (s, 4H, CH ), 3.13 (s, 12 H,
2
N(CH ) ), 2.07 (s, 18 H, N(CH ) ). C{ H} NMR
b
a
13
1
3
2
3 2
(
300 MHz, CDCl ): d = 137.9 (pyrrole, e), 106.9 (pyr-
3
c b
4.5. Synthesis and characterization of Ti(dap)(NMe2)3
(5)
role, d), 60.0 (C H ), 47.1 (N(CH ) ), 45.8
(
C: 53.19 (53.33). H: 10.09 (10.07). N: 22.82 (23.32).
2
3 2
a
N(CH ) ). Elemental analysis; experimental (Calc.),
3 2
Under an atmosphere of dry nitrogen, Ti(NMe ) (Cl)
2
3
(0.200 g, 0.929 mmol) was dissolved in 15 mL ether in a
4.4. Synthesis and characterization of
Ti (dap) (NHNMe )(NNMe ) (4)
filter flask. Lidap (0.121 g, 0.931 mmol) was dissolved in
5 mL ether in a vial. Both of them were cooled in the
cold well. Then Lidap solution was added to the solu-
tion of Ti(NMe ) (Cl) and allowed to warm up to the
2
3
2
2 2
2
3
room temperature and stir overnight. Then the solvent
was pumped down, and the residue was purified by crys-
tallization from ether as reddish-brown crystals in 77%
q
p
NMed
Mea
2
r
o
Mes
1
2
N
b
c
N Me NH
Mee
N
yield (0.218 g, 0.719 mmol). H NMR (300 MHz,
CDCl ): d = 6.80 (q, 1H, 5-pyrrolyl), 6.02 (t, 1H,
JHH = 2.6 Hz, 4-pyrrolyl), 5.82 (m, 1H, 3-pyrrolyl),
N
2
t
N
n
f
3
u
Ti
N
Ti
N
N
g
v
N
3
6
.51 (s, 2H, CH ), 3.22 (s, 18H, amido CH ), 2.36 (s,
2 3
h
13
H, amine CH3). C{ H} NMR (300 MHz, CDCl ):
1
m
x
Me
N
j
Mek
2
3
w
i
d = 142.9 (2-pyrrolyl), 133.3 (5-pyrrolyl), 122.0 (4-pyrr-
olyl), 107.5 (3-pyrrolyl), 65.2 (CH ), 53.3 (amido CH ),
Mel
2
3
51.6 (amine CH3).
All the manipulations were done inside a nitrogen
filled glove-box. In a vial, Ti(dap) (NMe ) (0.200 g,
0.500 mmol) was dissolved in toluene (250 lL). It was
then cooled in a liquid nitrogen-cooled cold well. To this
2
2 2
0
.6. Attempted reaction of 1-hexyne, N,N,N -
trimethylhydrazine, tert-butylisocyanide in presence of
4
Ti(dap) (NMe ) (1)
2 2 2
solution was added 1,1-Me NNH (76 lL, 1.00 mmol).
2
2
Then, the solution was allowed to warm up to room
temperature and stir for 1 h. The solution was kept in
the refrigerator at ꢀ35 ꢁC overnight. The volatiles were
removed in vacuo, and the reddish-brown residue was
crystallized from a 1:1 mixture of dichloromethane:pen-
Under an atmosphere of dry nitrogen, a threaded
pressure tube was loaded with toluene (300 lL), Ti
0
(
dap) (NMe ) (1) (0.023 g, 0.06 mmol), N,N,N -trim-
2 2
2
ethylhydrazine (0.044 g, 0.60 mmol), 1-hexyne (0.070
lL, 0.61 mmol), and tert-butyl isocyanide (68 lL, 0.60
mmol). The tube was sealed with a Teflon cap and
heated at 100 ꢁC for 16 h. The residue was analyzed
with GC-FID. Only starting materials were observed,
and no product was detected under these reaction
conditions.
tane to obtain 4 as yellow plates in 61% yield (0.195 g,
1
0
.305 mmol). H NMR (500 MHz, C D ): d = 7.68 (br,
6
6
1
H, c), 6.89 (br, 1H, r or x), 6.56 (t, 1H, JHH = 2.7 Hz,
q or w), 6.40 (t, 2H, JHH = 2.5 Hz, q or w and r or x),
.34 (br, 1H, p or v), 6.22 (br, 1H, j), 6.17 (t, 1H,
6
JHH = 2.6 Hz, i), 6.08 (br, 1H, p or v), 5.77 (br, 1H,
h), 3.99 (d, 1H, f, JHH = 13.8 Hz), 3.87 (d, 1H, n or t,
JHH = 13.8), 3.78 (d, 1H, n or t, JHH = 13.4), 3.57 (d,
4.7. X-ray crystallography
1
H, n or t, JHH = 13.4), 3.52 (d, 1H, n or t,
JHH = 13.8), 3.12 (d, 1H, f, JHH = 13.8), 2.95 (br, 3H,
a or b or k or l), 2.85 (br, 6H, m or s), 2.68 (br, 3H, a
or b or k or l), 2.42 (br, 6H, d), 2.32 (br, 3H, a or b
or k or l), 2.29 (br, 3H, a or b or k or l), 2.26 (br, 6H,
Crystals grown from concentrated solutions at
ꢀ35 ꢁC were moved quickly from a scintillation vial to
a microscope slide containing Paratone N. Samples were
selected and mounted on a glass fiber in wax and Par-
atone. The data collections were carried out at a sample
1
3
1
m or s), 1.86 (br, 6H, e). C{ H} NMR (500 MHz,

5076
S. Banerjee et al. / Journal of Organometallic Chemistry 690 (2005) 5066–5077
Table 2
Crystallographic data and structure refinement parameters for
Ti(NMe (bap) (3) and Ti (dap) (NHNMe )(NNMe (4)
Research Fund administered by the American Chemical
Society, the Office of Naval Research, and the Depart-
ment of Energy – Defense Programs. ALO is an Alfred
P. Sloan Fellow. ALO thank Jim Harrison and Ned
Jackson for helpful discussions concerning the computa-
tional studies.
2
)
3
2
3
2
2 2
)
3
4
Formula
C
16
36
H N
6
Ti
27 52 2
C H N12Ti
Formula weight
Crystal size (mm)
Crystal shape
360.41
640.61
0.32 · 0.68 · 0.71 0.59 · 0.84 · 0.96
Parallelpiped
174(2)
Parallelpiped
174(2)
Temperature (K)
Crystal system
Space group
Monoclinic
P2(1)/c
Triclinic
P(–1)
Appendix A. Supplementary data
Unit cell dimensions
˚
Crystallographic tables from X-ray diffraction exper-
iments. Crystallographic data for the structural analysis
have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC 264853 3 and 264854 for
4. Supplementary data associated with this article can
be found in the online version, at doi:10.1016/
j.jorganchem.2005.03.025.
a (A)
˚
9.3023(11)
11.1907(14)
19.610(2)
90
10.090(3)
10.859(4)
17.152(5)
75.86(3)
79.47(3)
65.23(3)
1647.8(9)
2
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
V (A )
Z
93.075(3)
90
˚
3
2038.4(4)
4
1.174
ꢀ
3
D (g cm
l (mm
)
1.291
0.522
ꢀ
1
)
0.429
2.08–23.28
17217
h range (ꢁ)
Reflections measured
2.10–23.29
7483
References
Independent reflections (Rint
Number of parameters
R(F) for I > 2r(I)
wR(F ) (all data)
2
GOF(F )
)
2937 (0.0782)
208
0.0592
4697 (0.0668)
385
0.0556
[
1] (a) For some reviews on multicomponent coupling reactions see I.
Ugi, B. Werner, A. D o¨ mling, Molecules 8 (2003) 53;
(
(
(
(
b) A. D o¨ mling, I. Ugi, Angew. Chem., Int. Ed. 39 (2000) 3168;
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2
0.1566
1.049
0.1430
1.043
Maximum, minimum
ꢀ3
0.543, ꢀ0.474
1.345, ꢀ0.515
d) R.W. Armstrong, A.P. Combs, P.A. Tempest, S.D. Brown,
˚
Dq (e A
)
T.A. Keating, Acc. Chem. Res. 29 (1996) 123;
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(2000) 3321.
(
6
temperature of 173 K on a Bruker AXS platform three-
circle goniometer with a CCD detector. The data were
processed and reduced utilizing the program SAINT-
PLUS supplied by Bruker AXS. The structures were
solved by direct methods (SHELXTL v5.1, Bruker AXS)
in conjunction with standard difference Fourier tech-
niques Table 2.
[
2] (a) For some examples of recent transition metal-catalyzed multi-
component coupling reactions see H.P. Hratchian, S.K. Chow-
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(
4
[
[
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.8. Computational details
4
099;
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The calculated molecular structures were obtained by
geometry optimizations at the DFT level using the
(
[
B3LYP functional using GaussianÕs default grid size
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[
29]. The geometry optimizations on Entry 1 of Table
were initially carried out using the STO3G basis set
1
and further refined with the 6-31++G** basis set to ob-
tain the listed energies. The molecules shown in Fig. 1
were placed near the desired geometry and optimized
to the local or global minimum for that conformation.
All calculations used the Gaussian-03M program [30]
as implemented on a G5 Macintosh desktop with dual
processors.
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5
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Acknowledgments
(
The authors appreciate the generous financial sup-
port of the National Science Foundation, the Petroleum
(

S. Banerjee et al. / Journal of Organometallic Chemistry 690 (2005) 5066–5077
5077
(
e) F. Basuli, B.C. Bailey, J. Tomaszewski, J.C. Huffman, D.J.
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(
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[
[
11] While the precatalyst Ti(NMe
2
)
3
(bap) (3) has only one of the
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scrutiny in our laboratory.
(
(
(
(
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