Carbometalation reactions of diphenylacetylene and other alkynes with methylalanes and titanocene derivatives

Article abstract of DOI:10.1021/om960879k

The reaction of PhC=CPh with methylalanes and titanocene derivatives is multi-mechanistic. In cases where 1:1 mixtures of Me₃Al or Me₂AlCl with Cl₂TiCp₂ or MeTiCp₂Cl are used, the reaction proceeds exclusively via methyltitanation, which needs to be promoted by a methylalane but is stoichiometric in both Ti and Al. The product of methyltitanation is ≥98% stereoisomerically pure (E)-1,2-diphenyl-1-propenyltitanocene chloride (10) complexed with methylalanes, from which 10 can be obtained as a pure substance. In cases where a 2:1 mixture of Me₃Al and Cl₂TiCp₂ is used, the course of reaction varies and is very much dependent on several reaction parameters. To observe the known formation of the Tebbe reagent (4) and its reaction with PhC≡CPh to give a titanacyclobutene 5, it is necessary to premix Me₃Al and Cl₂TiCp₂ in a 2:1 ratio for a few days and run the reaction in the presence of a base, e.g., DMAP. If no base is added, fast methyltitanation is observed with Me₃Al and Cl₂TiCp₂ before their conversion to 4. Even after the formation of 4, only slow methyltitanation of PhC≡CPh is observed in the absence of a base, presumably via formation of a MeTiCp₂-containing reagent from 4 and Me₂AlCl. Some other intricate aspects of the reaction are also discussed. The reaction of 5-decyne with a 1:1 mixture of Me₃Al and Cl₂TiCp₂ provides 6-methyl-4,5-decadiene in 92% yield, while the corresponding reaction of 1-octyne gives, after protonolysis, 2-methyl-1-octene only in 25% yield along with at least 3 unidentified but apparently dimeric products.

Full text of DOI:10.1021/om960879k

Organometallics 1997, 16, 951-957
951
Ca r bom eta la tion Rea ction s of Dip h en yla cetylen e a n d
Oth er Alk yn es w ith Meth yla la n es a n d Tita n ocen e
Der iva tives
Ei-ichi Negishi,* Denis Y. Kondakov, and David E. Van Horn†
Department of Chemistry, Purdue University, W. Lafayette, Indiana 47907
Received October 17, 1996X
The reaction of PhCtCPh with methylalanes and titanocene derivatives is multi-
mechanistic. In cases where 1:1 mixtures of Me3Al or Me2AlCl with Cl2TiCp2 or MeTiCp2Cl
are used, the reaction proceeds exclusively via methyltitanation, which needs to be promoted
by a methylalane but is stoichiometric in both Ti and Al. The product of methyltitanation
is g98% stereoisomerically pure (E)-1,2-diphenyl-1-propenyltitanocene chloride (10) com-
plexed with methylalanes, from which 10 can be obtained as a pure substance. In cases
where a 2:1 mixture of Me3Al and Cl2TiCp2 is used, the course of reaction varies and is very
much dependent on several reaction parameters. To observe the known formation of the
Tebbe reagent (4) and its reaction with PhCtCPh to give a titanacyclobutene 5, it is necessary
to premix Me3Al and Cl2TiCp2 in a 2:1 ratio for a few days and run the reaction in the
presence of a base, e.g., DMAP. If no base is added, fast methyltitanation is observed with
Me3Al and Cl2TiCp2 before their conversion to 4. Even after the formation of 4, only slow
methyltitanation of PhCtCPh is observed in the absence of a base, presumably via formation
of a MeTiCp2-containing reagent from 4 and Me2AlCl. Some other intricate aspects of the
reaction are also discussed. The reaction of 5-decyne with a 1:1 mixture of Me3Al and
Cl2TiCp2 provides 6-methyl-4,5-decadiene in 92% yield, while the corresponding reaction of
1-octyne gives, after protonolysis, 2-methyl-1-octene only in 25% yield along with at least 3
unidentified but apparently dimeric products.
Sch em e 1
In tr od u ction
We reported in 19781 that treatment of diphenyl-
acetylene with 2 equiv each of Me3Al and Cl2TiCp2 in
1,2-dichloroethane at 20-22 °C for 12 h produced, after
quenching with H2O, (Z)-R-methylstilbene (1) in 84%
yield by GLC along with a minor amount (<3%) of an
unidentified byproduct. Iodinolysis of the product gave
(E)-1-iodo-1,2-diphenylpropene (2) (g97% E) in 75%
yield by GLC. These results pointed to the formation
of an alkenylmetal represented by 3 (Scheme 1). How-
ever, it was not further characterized.
A few years later, Tebbe et al.2 reported that treat-
ment of diphenylacetylene with a reagent represented
by 4, commonly known as the Tebbe reagent3 and
preformed by mixing Cl2TiCp2 with 2 equiv of Me3Al
for 2-3 d at room temperature, in the presence of THF
or some other base produced a titanacyclobutene 5
(Scheme 2). It should be noted here that, in the two
reactions shown in Schemes 1 and 2, the three reac-
tants, i.e., Cl2TiCp2, Me3Al, and PhCtCPh, are identi-
cal, even though the products are totally different.
Sch em e 2
During the past few years, Petasis et al.4 and Doxsee
et al.5 have independently reported that Me2TiCp2 reacts
with PhCtCPh to give 5 and/or the methyltitanation
product 6. Although 6 can be slowly converted to 5 upon
prolonged heating,5 it must not be an intermediate in
the initial and relatively rapid formation of 5 at 75-80
°C.4 One plausible explanation for the dichotomous
behavior is that Me2TiCp2 undergoes R-H abstraction
to give CH2dTiCp2 (7) which rapidly adds to PhCtCPh
to give 5 in competition with methyltitanation of
Me2TiCp2 with PhCtCPh to give 6.4 The slow conver-
† Work by D.E.V.H. was performed at Syracuse University.
X Abstract published in Advance ACS Abstracts, February 15, 1997.
(1) Van Horn, D. E.; Valente, L. F.; Idacavage, M. J .; Negishi, E. J .
Organomet. Chem. 1978, 156, C20.
(2) Tebbe, F. N.; Harslow, R. L. J . Am. Chem. Soc. 1980, 102, 6149.
(3) Tebbe, F. N.; Parshall, G. W.; Reddy, G. S. J . Am. Chem. Soc.
1978, 100, 3611.
(4) Petasis, N. A.; Fu, D. K. Organometallics 1993, 12, 3776.
(5) Doxsee, K. M.; J uliette, J . J . J .; Mouser, J . K. M.; Zientara, K.
Organometallics 1993, 12, 4682.
S0276-7333(96)00879-5 CCC: $14.00 © 1997 American Chemical Society

952 Organometallics, Vol. 16, No. 5, 1997
Negishi et al.
Sch em e 3
Sch em e 5
Sch em e 4
Sch em e 6
sion of 6 into 5 is thought to proceed via rare γ-H
abstraction. Despite an apparent discrepancy between
the two studies 4,5 on the ease of thermal decomposition
of 6 to give 5, the nature of the dichotomy observed in
the reaction of Me2TiCp2 with PhCtCPh appears to be
reasonably clear (Scheme 3).
The structure of the Tebbe reagent (4)3 and the
mechanism of its formation from Cl2TiCp2 and Me3Al6
are both well clarified. The latter may be best repre-
sented by an R-H abstraction process shown in Scheme
4.6 Treatment of 4 with THF or some other base is
thought to generate 7 which can then add to diphenyl-
acetylene to give 5.2
Far less well established are the structure of 3 and
the nature of the dichotomous relationship between the
reactions shown in Schemes 1 and 2. The main goal of
this study is to present results and discussion shedding
some light on these aspects, thereby permitting fuller
understanding of the intriguingly multifaceted methyl-
titanation of alkynes. This study is also intended to
supplement our parallel study on the corresponding
reactions of alkynes with organoalanes and zirconocene
derivatives7 which have also displayed different but
related multimechanistic features.
MeTiCp2Cl (<2%). We then confirmed our previous
results1 that the reaction of diphenylacetylene with a
1:1 mixture (2 equiv each) of Me3Al and Cl2TiCp2 or
preformed 8 would produce, after iodinolysis, (E)-1-iodo-
1,2-diphenylpropene (2) in 80% yield. Examination of
the reaction mixture before quenching by NMR spec-
troscopy indicated the formation of titanocene deriva-
tives 9 in 81% yield. Also detectable was MeTiCp2Cl‚
AlMe2Cl (8) remaining unreacted to the extent of 11%.
No other Cp-containing species was detectable. After
treatment of the reaction mixture with Et2O and
removal of Al-containing compounds by washing with
Et2O, an Al-free titanocene derivative was isolated and
identified as 10 by NMR spectroscopy and high-resolu-
tion mass spectrometry. Its treatment with DCl-D2O
gave >95% isomerically pure (Z)-1-deuterio-1,2-diphen-
ylpropene (11) in 90% yield, the extents of D incorpora-
tion at the C-1 and C-3 positions being g95 and <5%,
respectively. It was stable at 22 °C for at least several
days. Its identity was further established by its conver-
sion by treatment with MeLi into 6.4,5 There was no
indication for the formation of 5. Similarly, the reaction
of diphenylacetylene with Me2AlCl-Cl2TiCp2 for 3 h at
22 °C produced, after quenching with Et2O, a 90% yield
of 10. We were a little surprised to find that even
MeAlCl2-Cl2TiCp2 reacted with diphenylacetylene to
give a methyltitanation product in 27% yield after 3 h
at 22 °C. However, this product was unstable under
the reaction conditions, and it completely decomposed
within 12 h. These experimental results are sum-
marized in Schemes 5 and 6.
Resu lts a n d Discu ssion
Rea ction of Dip h en yla cetylen e w ith 1:1 Mix-
tu r es of Meth yla la n es a n d Cl2TiCp 2. As reported
previously,6 treatment of Cl2TiCp2 with 1 equiv of Me3Al
for 1 h at 22 °C gave MeTiCp2Cl‚AlMe2Cl (8) exhibiting
13C NMR singlets at 60.24 and 117.33 ppm for the Ti-
bound Me and Cp, respectively. There was no indication
for the formation of Me2TiCp2. Its quenching with THF
provided MeTiCp2Cl8 (54.23 and 116.39 ppm for the Ti-
bound Me and Cp, respectively) in quantitative yield.
The reaction of Cl2TiCp2 with 1 equiv of Me2AlCl also
produced a methyltitanocene derivative. Although only
one set of 13C NMR signals were seen, quenching of the
reaction mixture with THF provided a mixture of
MeTiCp2Cl and Cl2TiCp2 in 66 and 29% yields, respec-
tively. The formation of Me2TiCp2 was not detectable.
Treatment of Cl2TiCp2 with MeAlCl2 under similar
conditions did not produce a detectable amount of
(6) Ott, K. C.; deBoer, E. J . M.; Grubbs, R. H. Organometallics 1984,
3, 223. See also: Clauss, K.; Bestian, H. J ustus Liebigs Ann. Chem.
1962, 654, 8.
(7) (a) Van Horn, D. E.; Negishi, E. J . Am. Chem. Soc. 1978, 100,
2252. (b) Negishi, E. Pure Appl. Chem. 1981, 53, 2333. (c) Yoshida, T.;
Negishi, E. J . Am. Chem. Soc. 1981, 103, 1276. (d) Negishi, E.; Yoshida,
T. J . Am. Chem. Soc. 1981, 103, 4985. (e) Negishi, E.; Van Horn, D.
E.; Yoshida, T. J . Am. Chem. Soc. 1985, 107, 6639.
Rea ction of Dip h en yla cetylen e w ith 2:1 Mix-
tu r es of Me3Al a n d Cl2TiCp 2. As previously re-
ported,3 treatment of Cl2TiCp2 with 2 equiv of Me3Al
for 3 d provided the Tebbe reagent 4. Complete con-
sumption of Cl2TiCp2 was observed by NMR spec-
troscopy. Addition of diphenylacetylene to the Tebbe
reagent in the presence of 4 equiv of 4-(dimethylamino)-
(8) (a) Long, W. P. J . Am. Chem. Soc. 1959, 81, 5312. (b) Beachell,
H. C.; Butler, S. A. Inorg. Chem. 1965, 4, 1133.

Carbometalation Reactions
Organometallics, Vol. 16, No. 5, 1997 953
Sch em e 7
Sch em e 8
pyridine (DMAP) at 22 °C for 1 h led to smooth
formation of 55 which, upon treatment with DCl-D2O,
gave (Z)-1,3-dideuterio-1,2-diphenylpropene in 93% yield.
The extents of D incorporation at the C-1 and C-3
positions were >90 and >87%, respectively. In the
absence of DMAP or any other added base, however, a
totally different and very slow reaction took place under
otherwise the same conditions. After 24 h at 22 °C, the
product obtained in 86% yield after deuterolysis was 11.
Addition of DMAP to the reaction mixture after 24 h
did not change the outcome of deuterolysis. Although
D incorporation at the C-1 position was about 90%, that
at the C-3 position was only <5%. It is likely that
Me2AlCl formed as a byproduct reacts with 4 to generate
an equilibrium quantity of a methyltitanocene deriva-
tive which may tentatively be represented as MeTiCp2-
Cl‚Me(Cl)AlCH2AlMe2 and reacts with diphenylacet-
ylene to undergo methyltitanation. The formation of
MeTiCp2Cl‚Me(Cl)AlCH2AlMe2 may occur via substitu-
tion of the Me2AlCH2 group in 4 with Me. Similar
reactions producing polymethyl(methylene)aluminum
derivatives have been previously reported by other
workers.9 These results are summarized in Scheme 7.
To further clarify the relationship between our meth-
yltitanation reaction and Tebbe’s reaction which pro-
duced 5 via 4,2 Me3Al and Cl2TiCp2 were mixed in a 2:1
ratio, and diphenylacetylene was added to this mixture
within several minutes at 22 °C. Protonolysis after 24
h afforded a 90:10 mixture of the Z and E isomers of
1,2-diphenylpropene in 95% combined yield. After 5 d
at 22 °C the Z-to-E ratio decreased to 81:19 even though
the combined yield remained essentially the same at
91%. An essentially 1:1 mixture of the E and Z isomers
was obtained in 82% yield by heating the reaction
mixture at 75 °C for 24 h. Deuterolysis with DCl-D2O
after 5 d incorporated D only at the C-1 position, the D
incorporation at the C-3 center being <5%. Signifi-
cantly, there was no indication for the formation of 5
under these conditions.
The foregoing results suggested to us that it should
be possible to observe simultaneously both the straight-
forward methyltitanation reaction1 and the cyclic proc-
ess producing 52 in one reaction mixture. Indeed, when
a 2:1 mixture of Me3Al and Cl2TiCp2 was stirred at 22
°C for 24 h in C6D6, its analysis by NMR spectroscopy
indicated the formation of 4 and MeTiCp2Cl complexed
with methylalanes in 59 and 29% yields, respectively.
Addition of diphenylacetylene followed, 3 h later, by
DMAP at 22 °C produced, after deuterolysis, a roughly
70:30 mixture of (Z)-1-monodeuterio- and (Z)-1,3-dideu-
terio-1,2-diphenylpropenes in 95% combined yield. The
overall D incorporation at the C-1 position was >90%.
Here again, omission of DMAP led only to the straight-
forward methyltitanation reaction which produced within
1 h at 22 °C (Z)-1,2-diphenylpropene in 45% yield, after
protonolysis, with 50% of diphenylacetylene remaining
unreacted. When this reaction was continued for 24 h,
the only alkene product obtained in 90% yield after
deuterolysis was (Z)-1-monodeuterio-1,2-diphenylpro-
pene (Scheme 8).
It now is very clear that there are at least three
critical factors for observing the formation of 5 via 4,
(9) Sinn, H.; Hinck, H.; Bandermann, F.; Gru¨tzmacher, H. F. Angew.
Chem., Int. Ed. Engl. 1968, 7, 217.

954 Organometallics, Vol. 16, No. 5, 1997
Negishi et al.
Sch em e 9
Sch em e 10
i.e., (i) an excess of Me3Al relative to Cl2TiCp2, (ii)
deferment of addition of diphenylacetylene to allow
completion of the formation of 4, and (iii) use of a base,
such as DMAP, to induce the formation of 7 as an active
cyclization reagent. Unless all of these requirements
are satisfied, the straightforward methyltitanation reac-
tion is observed even with a mixture of 4 and Me2AlCl.
It is also noteworthy that, unlike 6 which was reported
to slowly produce 54,5 presumably via intramolecular γ
C-H activation, 10 did not show any sign of γ C-H
activation leading to the formation of 5. In contrast
with MeLi and methylmagnesium halides, Me3Al does
not readily methylate monoorganyltitanocene chlorides.
In principle, 10 could undergo bimetallic γ C-H activa-
tion. A related bimetallic R C-H activation shown in
Scheme 4 is known,6 and we have recently demonstrated
that bimetallic â C-H activation can play a significant
role in Zr-catalyzed carboalumination of alkynes.10
These processes are thought to be six-centered and
seven-centered, respectively. If 10 were to undergo a
related bimetallic γ C-H activation, such a process
would be eight-centered and hence potentially unfavor-
able (Scheme 9).
Bim eta llic a n d Stoich iom etr ic Na tu r e of th e
Meth yltita n a tion of Dip h en yla cetylen e. Neither
methylalanes,11 i.e., Me3Al, Me2AlCl, and MeAlCl2, nor
preformed MeTiCp2Cl reacts with diphenylacetylene
under the conditions that are satisfactory for the reac-
tion of diphenylacetylene with MenAlCl3-n-Cl2TiCp2,
where n ) 3 or 2, clearly indicating that both Al and Ti
are necessary at the crucial step of methyltitanation (net
addition of Me and Ti to alkynes or alkenes regardless
of its precise mechanism). The fact that the products
are alkenyltitanocene derivatives, e.g., 10, has estab-
lished the stoichiometric nature of the reaction with
respect to Ti. Indeed, the reaction of diphenylacetylene
with 3 equiv of Me3Al with 0.2 equiv of Cl2TiCp2
produced, after protonolysis, (Z)- and (E)-1,2-diphenyl-
proprene only in 14 and 4% yields, respectively. This
is a sharp contrast with the catalytic nature of the
corresponding reaction of MenAlCl3-n-Cl2ZrCp2 with
respect to Zr7 and the reaction of alkenes with Et2AlCl
catalyzed by titanium tetraalkoxides.12 The methyl-
titanation reaction reported herein is not catalytic in
Al either. Thus, the reaction of diphenylacetylene with
1 equiv of preformed MeTiCp2Cl8 and 0.2 equiv of Me3Al
Sch em e 11
or Me2AlCl gave the desired carbotitanation product
only up to 20% yield based on Ti. Methylalanes are
therefore stoichiometric promoters. Our attempts to
find alternate promoters or potential catalysts have thus
far failed. Specifically, no desired methyltitanation
products were obtained in the reactions of diphenyl-
acetylene with 1 equiv of MeTiCp2Cl in the presence of
BCl3 or SnCl4, further pointing to the uniquely effective
nature of the Al-Ti bimetallic systems. We tentatively
propose a mechanism involving a concerted direct
addition of the C-Ti bond activated by Al represented
by Scheme 10, but a few other alternatives including
some six-centered processes cannot be rigorously ruled
out on the basis of the currently available data.
Reaction s of 5-Decyn e an d 1-Octyn e with Me3Al-
Cl2TiCp 2. The reactions of alkyl-substituted internal
and terminal alkynes have been only briefly investi-
gated. The following results are presented here mainly
to provide a proper perspective of the scope and limita-
tions of the carbotitanation of alkynes with Me3Al-
Cl2TiCp2, even though full delineation of the scope will
require extensive further studies. The reaction of
5-decyne with 2 equiv each of Me3Al and Cl2TiCp2 in
1,2-dichloroethane at 22 °C for 3 h produced, after
hydrolytic workup, a 92% GLC yield of 6-methyl-4,5-
1
decadiene (12) exhibiting a well-defined H NMR mul-
tiplet at 4.7-5.1 ppm, 13C NMR signals at 90.08, 99.12,
and 191.00 ppm, and an IR absorption at 1970 (w) cm-1
characteristic of an allene. Attempted iodination and
deuteration of the presumed intermediate 13 did not
produce 14 and 15, respectively, indicating that 13 must
have been converted into 12 before workup (Scheme 11).
Thus, although potentially attractive as a method for
the preparation of allenes, the reaction with Me3Al-
Cl2TiCp2 reagent system does not provide alkenylmetals
as products.
(10) Negishi, E.; Kondakov, D. Y.; Choueiry, D.; Kasai, K.; Taka-
hashi, T. J . Am. Chem. Soc. 1996, 118, 9577.
The reaction of 1-octyne with 2 equiv each of Me3Al
and Cl2TiCp2 under the same conditions as for the
reaction of 5-decyne provided, after quenching with 3
N HCl, 2-methyl-1-octene in 25% GLC yield and a
mixture of at least 3 higher boiling and apparently
dimeric products which were not identified. Several
attempts to improve the yield of 2-methyl-1-octene, such
as running the reaction at -20 °C, were unsuccessful.
(11) At much higher temperatures organoalanes are known to
undergo carboalumination with internal alkynes to give mainly
oligomeric products, while terminal alkynes are mainly converted to
alkynylalanes: (a) Mole, T.; J effery, E. A. Organoaluminium Com-
pounds; Elsevier Publishing Co.: Amsterdam, 1972. (b) Zweifel, G.;
Miller, J . A. Org. React. 1984, 32, 375.
(12) (a) Dzhemilev, U. M.; Ibragimov, A. G.; Vostrikova, O. S.;
Tolstikov, G. A.; Zelenova, L. M. Izv. Akad. Nauk SSSR, Ser. Khim.
1981, 361. (b) Negishi, E.; J ensen, M. D.; Kondakov, D. Y.; Wang, S.
J . Am. Chem. Soc. 1994, 116, 8404.

Carbometalation Reactions
Con clu sion s
Organometallics, Vol. 16, No. 5, 1997 955
MeTiCp2Cl was formed in 66% yield along with Cl2TiCp2 (29%),
as judged from the 13C NMR signals of the Cp groups at δ
115.95 and 120.25, respectively.
Rea ction of Cl2TiCp 2 w ith MeAlCl2. To Cl2TiCp2 (0.25
g, 1 mmol) and 5 mL of C6D6 was added MeAlCl2 (1 mL, 1 M
in hexanes). The reaction mixture was stirred for 1 h at 22
°C. After quenching of the reaction with THF (0.2 mL), NMR
examination indicated that essentially all of that Cl2TiCp2
remained unreacted. The extent of the formation of MeTiCp2Cl
was e2%.
The multimechanistic nature of the reaction of di-
phenylacetylene with methylalane-titanocene reagent
systems has been clarified in considerable detail.
1. One-to-one mixtures of Me3Al or Me2AlCl with
Cl2TiCp2 provide MeTiCp2Cl derivatives. These mix-
tures react with diphenylacetylene to give (E)-1,2-
diphenyl-1-propenyltitanocene derivatives via Al-pro-
moted stoichiometric syn-methyltitanation. After
removal of organoalanes as their ether complexes, pure
(E)-1,2-diphenyl-1-propenyltitanocene chloride may be
obtained in good yield. Its deuterolysis gives 1-deuterio-
1,2-diphenylpropene.
2. The corresponding reaction of diphenylacetylene
with a 2:1 mixture of Me3Al and Cl2TiCp2 is much more
complex and condition dependent. If Me3Al and Cl2TiCp2
is premixed in a 2:1 ratio for 3 d to produce the Tebbe
reagent and then reacted with diphenylacetylene in the
presence of DMAP, the known formation of a titana-
cyclobutene 5 is observed. Deuterolysis of 5 indeed
gives (Z)-1,3-dideuterio-1,2-diphenylpropene. In the
absence of DMAP, however, the methyltitanation reac-
tion takes place slowly over 24 h. If all three reagents
are mixed essentially at once, only the methyltitanation
reaction of diphenylacetylene is observed. However, an
excess of Me3Al induces partial stereoisomerization.
When 2 equiv of Me3Al and Cl2TiCp2 is mixed only for
24 h and then reacted with diphenylacetylene, the
reaction proceeds partially to undergo methyltitanation
and partially to produce a titanacyclobutene 5 in the
presence of DMAP.
Rea ction of a 1:1 Mixtu r e of Cl2TiCp 2 a n d Me3Al w ith
Dip h en yla cetylen e. To Cl2TiCp2 (0.25 g, 1 mmol), 5 mL of
(CH2Cl)2, and diphenylacetylene (178 mg, 1 mmol) was added
Me3Al (0.5 mL, 2 M in toluene). The reaction mixture was
stirred for 24 h at 22 °C. NMR examination indicated that
11% of MeTiCp2Cl‚AlMe2Cl was present along with 81% of 9,
as judged by quantitative analysis of the 1H NMR signals of
the Cp groups: δ 6.03 and 6.15, respectively. The reaction
mixture was treated with 5 mL of Et2O, and the precipitate
was allowed to settle. The clear supernatant layer was
removed by canula decantation. This washing procedure was
applied 3 times, and the residual red powder was dried under
vacuum to give 10 (273 mg, 67%): 1H NMR (CD2Cl2, Me4Si) δ
1.65 (s, 3 H), 6.50 (s, 10 H), 6.80-7.30 (m, 10 H); 13C NMR
(CD2Cl2, Me4Si) δ 27.50, 115.76, 124.24, 124.96, 127.20, 127.46,
128.21, 130.57, 138.35, 147.71, 149.60, 187.09. HRMS/FAB
calcd for C25H23Ti ([M - Cl]) m/ z 371.1279, found m/ z
371.1283.
Rea ction of 10 w ith DCl-D2O. A suspension of 10 (0.2
g, 0.5 mmol) in 5 mL of benzene was treated with 1 mL of
10% DCl in D2O for 1 h at 22 °C. The reaction mixture was
extracted with Et2O, washed with water, dried over MgSO4,
filtered, and concentrated. Column chromatography on silica
gel afforded 88 mg of 11 (90%): 1H NMR (CDCl3, Me4Si) δ
2.15 (s, 3 H), 6.95-7.35 (m, 10 H); 13C NMR (CDCl3, Me4Si) δ
27.05, 126.03, 126.56 (t, J ) 24 Hz), 126.84, 127.78, 128.09,
128.40, 128.89, 137.51, 138.57, 142.00.
Rea ction of 10 w ith MeLi. A suspension of 10 (0.2 g, 0.5
mmol) in 5 mL of toluene was treated at 0 °C with MeLi (0.7
mL, 1.4 M in ether, 1.0 mmol). The reaction mixture was
stirred at 22 °C for 1 h, and the solvent was evaporated. The
resultant solid was dissolved in 5 mL of C6D6 and examined
by NMR spectroscopy, which indicated that 64,5 was formed
in 77% yield: 1H NMR (C6D6, Me4Si) δ -0.41 (s, 3 H), 1.46 (s,
3 H), 5.86 (s, 10 H), 6.65-7.05 (m, 10 H).
Rea ction of a 1:1 Mixtu r e of MeTiCp 2Cl a n d Me2AlCl
w ith Dip h en yla cetylen e. To MeTiCp2Cl (1.1 mL, 1 mmol,
0.9 M in C6D6), 5 mL of (CH2Cl)2, and diphenylacetylene (178
mg, 1 mmol) was added Me2AlCl (1 mL, 1 M in hexanes). The
reaction mixture was stirred for 24 h at 22 °C. NMR
examination indicated that 9 was formed in 85% yield, as
judged by quantitative analysis of the 1H NMR signal of the
Cp group (δ 6.15).
3. The reaction of 5-decyne with a 1:1 mixture of
Me3Al and Cl2TiCp2 gives 6-methyl-4,5-decadiene. Nei-
ther deuterium nor iodine is incorporated into the
product. The corresponding reaction of 1-octyne gives,
after protonolysis, 2-methyl-1-octene only in 25% yield
along with at least three unidentified but apparently
dimeric products.
Exp er im en ta l Section
Gen er a l P r oced u r es. Manipulations involving organo-
metallics were carried out under an atmosphere of N2 or Ar.
Hexanes, 1,2-dichloroethane, benzene, and toluene were dis-
tilled from CaH2; tetrahydrofuran was distilled from sodium
benzophenone ketyl. MeTiCp2Cl was prepared according to
the published procedure.8 The other starting materials were
1
purchased from commercial sources and used as received. H
Rea ction of a 1:1 Mixtu r e of Cl2TiCp 2 a n d Me2AlCl
w ith Dip h en yla cetylen e. To Cl2TiCp2 (0.25 g, 1 mmol), 5
mL of (CH2Cl)2, and diphenylacetylene (178 mg, 1 mmol) was
added Me2AlCl (1 mL, 1 M in hexanes). The reaction mixture
was stirred for 3 h at 22 °C. NMR examination indicated that
10 complexed with MeAlCl2 was formed in 90% yield, as judged
and 13C NMR spectra were recorded on Varian Gemini-200,
Varian VXR-500S, and GE QE PLUS 300 spectrometers.
Rea ction of Cl2TiCp 2 w ith Me3Al.6 To Cl2TiCp2 (0.25 g,
1 mmol) and 5 mL of C6D6 was added at 22 °C Me3Al (0.5 mL,
2 M in toluene). The reaction mixture was stirred for 1 h at
22 °C. NMR examination indicated that 8 was formed
quantitatively: 1H NMR (C6D6, Me4Si) δ -0.12 (br s, 6 H), 0.96
(s, 3 H), 5.79 (s, 10 H); 13C NMR (C6D6, Me4Si) δ 60.24, 117.33.
After quenching of the reaction with THF (0.2 mL), NMR
examination indicated that MeTiCp2Cl8 was formed
quantitatively: 1H NMR (C6D6, Me4Si) δ 0.85 (s, 3 H), 5.76 (s,
10 H); 13C NMR (C6D6, Me4Si) δ 49.43, 115.69.
1
by quantitative analysis of the H NMR signal of the Cp group
(δ 6.20).
Rea ction of a 1:1 Mixtu r e of Cl2TiCp 2 a n d MeAlCl2
w ith Dip h en yla cetylen e. To Cl2TiCp2 (0.25 g, 1 mmol), 5
mL of (CH2Cl)2, and diphenylacetylene (178 mg, 1 mmol) was
added MeAlCl2 (1 mL, 1 M in hexanes), and the reaction
mixture was stirred for 3 h at 22 °C. NMR examination
indicated that 10 complexed with a methylalane was formed
in 27% yield, as judged by quantitative analysis of the 1H NMR
signal of the Cp group (δ 6.16). After 12 h at 22 °C no signals
attributable to Cp were visible in the 1H and 13C spectra.
Rea ction of 4 w ith Dip h en yla cetylen e in th e P r esen ce
of N,N-Dim eth yl-4-a m in op yr id in e (DMAP ). Meth od a .
Rea ction of Cl2TiCp 2 w ith Me2AlCl. To Cl2TiCp2 (0.25
g, 1 mmol) and 5 mL of C6D6 was added Me2AlCl (1 mL, 1 M
in hexanes). The reaction mixture was stirred for 1 h at 22
°C. NMR examination showed a single set of 13C NMR
signals: 64.56 (CH3-Ti), 118.14 (Cp). After quenching of the
reaction with THF (0.2 mL), NMR examination indicated that

956 Organometallics, Vol. 16, No. 5, 1997
Negishi et al.
The following procedure is based on a previous study by Tebbe
et al.2,3 To Cl2TiCp2 (0.25 g, 1 mmol) and 5 mL of toluene was
added Me3Al (1.0 mL, 2 M in toluene, 2 mmol). After the
mixture was stirred for 3 days at 22 °C, diphenylacetylene (178
mg, 1 mmol) and DMAP (0.49 g, 4 mmol) were successively
added. After quenching of the reaction with 4% DCl in D2O
(5 mL) at 0 °C, the reaction mixture was extracted with Et2O,
washed with water, dried over MgSO4, filtered, and concen-
trated. Column chromatography on silica gel (hexanes) af-
forded 182 mg (93%) of (Z)-1,3-dideuterio-1,2-diphenylpro-
pene: 1H NMR (CDCl3, Me4Si) δ 2.13 (s, 2 H), 6.90-7.40 (m,
10 H); 13C NMR (CDCl3, Me4Si) δ 26.71 (t, J ) 20 Hz), 126.03,
126.50 (t, J ) 23 Hz), 126.84, 127.77, 128.07, 128.39, 128.86,
137.43, 138.43, 141.99.
Meth od c. The reaction mixture prepared as described
above was treated with SnCl4 (0.12 mL, 1 mmol) and stirred
for 24 h at 22 °C. GLC analysis of a quenched (3 N HCl)
aliquot indicated that diphenylacetylene remained unreacted
to the extent of 95%. The amount of 1,2-diphenylpropene was
below the detection limit of 1%.
Rea ction of Dip h en yla cetylen e w ith Me3Al in th e
P r esen ce of a Ca ta lytic Am ou n t of Cl2TiCp 2. To Cl2TiCp2
(0.05 g, 0.2 mmol), 5 mL of (CH2Cl)2, and diphenylacetylene
(178 mg, 1 mmol) was added Me3Al (0.5 mL, 2 M in toluene,
1 mmol). The reaction mixture was stirred for 3 h at 60 °C.
GLC analysis of a quenched (3 N HCl) aliquot indicated that
75% of diphenylacetylene remained unreacted. The yields of
(Z)- and (E)-1,2-diphenylpropenes were 14 and 4%, respec-
tively.
Meth od b. Examination of the mixture of Me3Al and
Cl2TiCp2, prepared as described above, by NMR spectroscopy
after 24 h at 22 °C indicated the formation of 4 (59%) and
MeTiCp2Cl‚AlMenCl3-n (29%), as judged by quantitative analy-
sis of the Cp signals: 1H δ 5.63, 13C δ 112.27 and 1H δ 5.67,
13C δ 117.66, respectively. Diphenylacetylene (178 mg, 1
mmol) was added, and the reaction mixture was stirred for 1
h. After quenching of an aliquot (ca. 2 mL) with 3 N HCl at
0 °C, GLC examination showed that (Z)-1,2-diphenylpropene
was formed in 45% yield, and diphenylacetylene remained
unreacted to the extent of 50%. The reaction mixture was
stirred for 3 h, treated with DMAP (0.25 g, 2 mmol), stirred
for 1 h, and quenched with 4% DCl in D2O. Examination by
GLC and NMR spectroscopy showed that a mixture 11 and
its 1,3-dideuterio analogue was formed in 95% combined yield
(>90% D at C-1, 30% D at C-3).
Rea ction of 4 w ith Dip h en yla cetylen e in th e Absen ce
of DMAP . To Cl2TiCp2 (0.25 g, 1 mmol) and 5 mL of toluene
was added Me3Al (1.0 mL, 2 M in toluene, 2 mmol). After
stirring of the mixture for 3 days at 22 °C, diphenylacetylene
(178 mg, 1 mmol) was added. Examination of the reaction
mixture by GLC revealed that diphenylacetylene was con-
sumed after 24 h at 22 °C. After quenching of an aliquot (ca.
2 mL) with 4% DCl in D2O at 0 °C, examination by GLC and
NMR spectroscopy showed that 11 was formed in 86% yield
(>90% D at C-1, <5% D at C-3). The rest of the reaction
mixture was treated with DMAP (0.25 g, 2 mmol), stirred for
1 h, and quenched with 4% DCl in D2O. Its analysis as above
showed that 11 was formed in 86% yield (>90% D at C-1, <5%
D at C-3) indicating that DMAP had no effect on the reaction.
Rea ction of Dip h en yla cetylen e w ith Me2AlCl in th e
P r esen ce of a Ca ta lytic Am ou n t of MeTiCp 2Cl. To
MeTiCp2Cl (0.046 g, 0.2 mmol), 5 mL of (CH2Cl)2, and
diphenylacetylene (178 mg, 1 mmol) was added Me2AlCl (1
mL, 1 M in hexanes, 1 mmol) The reaction mixture was stirred
for 3 h at 60 °C. GLC analysis of a quenched (3 N HCl) aliquot
indicated that 75% of diphenylacetylene remained unreacted.
The yields of (Z)- and (E)-1,2-diphenylpropene were 17% and
4%, respectively.
Rea ction of Cl2TiCp 2 w ith (E)-(1-Bu tyl-2-m eth yl-1-
h exen yl)d im eth yla la n e. To Cl2TiCp2 (0.25 g, 1.0 mmol) and
5 mL of CH2Cl2 was added dropwise at -78 °C (E)-(1-butyl-
2-methyl-1-hexenyl)dimethylalane (2 mL, ca. 0.5 M in CH2Cl2).
The reaction mixture was warmed to 22 °C. After 15 min at
22 °C Cl2TiCp2 was fully dissolved. Examination of a quenched
(THF) aliquot by NMR spectroscopy indicated the formation
of an 85% yield of MeTiCp2Cl: 1H NMR (C6D6-CH2Cl2, Me4Si)
δ 0.93 (s, 3 H), 6.01 (s, 10 H); 13C NMR (C6D6, Me4Si) δ 49.38,
115.90. Examination of a quenched (3 N HCl) aliquot by GLC
indicated that (Z)-5-methyl-5-decene was formed to the extent
of 90% along with 6-methyl-4,5-decadiene (8%). After stirring
of the reaction mixture for 3 h at 22 °C, examination by NMR
spectroscopy and GLC indicated the formation of the following
compounds in the yields shown in parentheses: MeTiCp2Cl
(50%), (Z)-5-methyl-5-decene (60%), and 6-methyl-4,5-decadi-
ene (20%). No 13C NMR signal attributable to dCsTi was
observed (detection limit <5%).
R ea ct ion of Cl2TiCp 2 w it h 2 equ iv of (Z)-(1-Bu t yl-2-
m eth yl-1-h exen yl)lith iu m F ollow ed by 1 equ iv of I2. To
Cl2TiCp2 (0.25 g, 1.0 mmol) and 5 mL of toluene was added
dropwise at -78 °C (Z)-(1-butyl-2-methyl-1-hexenyl)lithium (5
mL, ca. 0.4 M in Et2O/pentane, 2 mmol). The reaction mixture
was warmed to -23 °C, stirred for 1 h, and treated with I2 (2
mL, 0.5 M in THF, 1 mmol). After warming of the reaction
mixture to 22 °C, the solvent was removed in vacuo. After
addition of 2 mL of CD2Cl2, the product was examined by NMR
spectroscopy. No 13C NMR signal attributable to dCsTi was
observed (detection limit <5%).
6-Meth yl-4,5-d eca d ien e via th e Rea ction of 5-Decyn e
w ith Me3Al-Cl2TiCp 2. To a brick-red colored slurry of
Cl2TiCp2 (4.98 g, 20 mmol) in 30 mL of (CH2Cl)2 was added
Me3Al (1.92 mL, 20 mmol) at 22 °C. To the resultant deep
dark orange solution was added 5-decyne (1.83 mL, 10 mmol).
After 3 h at 22 °C, the blue-green reaction mixture was
quenched with H2O. Analysis by GLC indicated the clean
formation of 6-methyl-4,5-decadiene in 92% yield. The stand-
Rea ction of a 1:2 Mixtu r e of Cl2TiCp 2 a n d Me3Al w ith
Dip h en yla cetylen e in th e Absen ce of DMAP . To Cl2TiCp2
(0.25 g, 1 mmol) and 5 mL of toluene was added Me3Al (1.0
mL, 2 M in toluene, 2 mmol). After stirring of the mixture
for 2 min at 22 °C, diphenylacetylene (178 mg, 1 mmol) was
added. After stirring of the reaction mixture for 24 h at 22
°C, quenching of an aliquot (ca. 2 mL) with 3 N HCl at 0 °C
followed by GLC examination showed that 1 was formed in
85% yield along with an 8% yield of its E isomer. After being
stirred for 5 days at 22 °C, the reaction mixture was quenched
with 4% DCl in D2O at 0 °C. Examination by GLC and NMR
spectroscopy revealed that 11 was formed in 74% yield (94%
D at C-1, < 5% D at C-3) along with a 17% yield of its E isomer.
Rea ction of MeTiCp 2Cl w ith Dip h en yla cetylen e in th e
Absen ce of Alk yla lu m in u m Com p ou n d s. Meth od a . To
MeTiCp2Cl (0.23 g, 1 mmol) and 5 mL of (CH2Cl)2 was added
diphenylacetylene (178 mg, 1 mmol). After the mixture was
stirred for 24 h at 22 °C, analysis by NMR spectroscopy and
GLC indicated that the starting materials remained intact to
the extent of 95%. The reaction mixture was then heated for
4 h at 80 °C without any change in the NMR spectra.
ard workup and chromatographic isolation afforded a pure
1
sample of the title compound: n18.4 1.4516; H NMR (CCl4,
D
Me4Si) δ 0.7-1.1 (m, 6 H), 1.1-1.6 (m, 6 H), 1.62 (d, J ) 3 Hz,
3 H), 1.7-2.2 (m, 4 H), 4.7-5.1 (m with at least 9 signals
centered at 4.90, J ) 3 Hz, 1 H); 13C NMR (CDCl3, Me4Si) δ
13.75, 14.05, 19.36, 22.60, 22.79, 30.10, 31.82, 34.07, 90.08,
99.12, 191.00; IR (neat) 2900 (s), 1970 (w), 1460 (m), 1375 (w)
cm-1. Anal. Calcd for C11H20: C, 86.76; H, 20.16. Found: C,
86.49; H, 20.08.
Meth od b. The reaction mixture prepared as described
above was treated with BCl3 (1 mL, 1 mmol, 1 M in heptane)
and stirred for 24 h at 22 °C. GLC analysis of a quenched (3
N HCl) aliquot indicated that diphenylacetylene remained
unreacted to the extent of 95%. The amount of 1,2-diphenyl-
propene was below the detection limit of 1%.
Rea ction of 1-Octen e w ith 2 equ iv Ea ch of Me3Al a n d
Cl2TiCp 2. The reaction of 1-octene (1.50 mL, 10 mmol) with

Carbometalation Reactions
Organometallics, Vol. 16, No. 5, 1997 957
Me3Al-Cl2TiCp2 as in the preceding experiment was mildly
exothermic and complete within 1 h. After quenching of the
reaction with 3 N HCl, analysis by GLC indicated the forma-
tion of 2-methyl-1-octene in 25% yield along with at least 3
unidentified and apparently dimeric compounds produced in
considerable amounts. In view of the low yield of the desired
product, the reaction was not further investigated.
Ack n ow led gm en t. We thank the National Science
Foundation (Grant CHE-9402288) for support of this
research. We acknowledge that Louis F. Valente,
Michael J . Idacavage, and Wenke Li performed some
experiments related to this work.
OM960879K