Multiple mechanistic pathways for zirconium-catalyzed carboalumination of alkynes. Requirements for cyclic carbometalation processes involving C-H activation

Article abstract of DOI:10.1021/ja9538039

The reactions of internal and terminal alkynes with organoalanes containing Et, n-Pr, and i-Bu groups in the presence of Cp₂ZrCl₂ and MeZrCp₂Cl were investigated with the goal of clarifying mechanistic details of some representative cases. Three fundamentally different processes, i.e., (i) C-M bond addition without C-H activation in the alkyl group, (ii) cyclic C-M bond addition via C-H activation, and (iii) hydrometalation, have been observed, and the courses of these reactions significantly depend on (i) the nature and number of alkyl groups in organoalanes, (ii) their amounts, and (iii) solvents. The reaction of alkynes with Et₃Al in the presence of 0.1 equiv of Cp₂ZrCl₂ in nonpolar solvents, e.g., hexanes, proceeds via C-H activation to give the corresponding aluminacyclopentenes. Investigation of the reaction of 5-decyne with 1-3 equiv of Et₃Al and 1 equiv of Cp₂ZrCl₂, which gave mono-, di-, or trideuterated (Z)-5-ethyl-5-decene as shown, together with the previously reported structural study on the reaction of Et₃Al with Cp₂ZrCl₂ leading to the formation of well-characterized bimetallic species 9, 10, and 11, supports a catalytic cycle involving bimetallic species 10 and 18. In summary, this process requires a zirconocene derivative containing one Zr-bound Et group which is linked to Et₃Al (but not to Et₂AlCl) through a Cl bridge, i.e., 18, to produce 10 via β C-H activation. In sharp contrast, the reaction of Et₂AlCl-Cp₂ZrCl₂ as well as of (n-Pr)₂AlCl-Cp₂ZrCl₂ does not involve any C-H activation processes. It proceeds well in chlorinated hydrocarbon solvents, e.g., (CH₂Cl)₂, but it is extremely sluggish in nonpolar solvents, e.g., hexanes. The reaction may well involve direct C-Al bond addition to alkynes, as suggested earlier for Zr-catalyzed Me-Al bond addition to alkynes, but a few other alternatives cannot be ruled out on the basis of the currently available data. The reaction of alkynes with (n-Pr)₃Al-Cp₂ZrCl₂ in nonpolar solvents proceeds partially via C-H activation and partially via hydrometalation. In contrast with the C-H activation process observed with Et₃Al, that with (n-Pr)₃Al is totally dominated by dimerization of alkynes to give aluminacyclopentadienes rather than aluminacyclopentenes, reflecting a previously established generalization that propene can be much more readily displaced from Zr by alkynes than ethylene. Hydrometalation is the exclusive process with (i-Bu)₃Al-Cp₂ZrCl₂. This hydrometalation reaction, however, reveals a few interesting complications. Alkyl-substituted internal alkynes give double bond migrated products in addition to the expected hydrometalation products. With terminal alkynes the reaction produces the expected hydrometalation products and the 1,1-dimetalloalkanes in comparable yields. Various other related reactions involving other alkynes, e.g., PhC≡CPh, n-OctC≡CH, and PhC≡CH, and other reagents, e.g., Et₃Al-MeZrCp₂Cl, Et₂AlCl-MeZrCp₂Cl, and (n-Pr)₃Al-MeZrCp₂Cl, were also studied.

Full text of DOI:10.1021/ja9538039

J. Am. Chem. Soc. 1996, 118, 9577-9588
9577
Multiple Mechanistic Pathways for Zirconium-Catalyzed
Carboalumination of Alkynes. Requirements for Cyclic
Carbometalation Processes Involving C-H Activation
Ei-ichi Negishi,*,† Denis Y. Kondakov,† Danie`le Choueiry,† Kayoko Kasai,‡,§ and
Tamotsu Takahashi*,‡,
Contribution from the Department of Chemistry, Purdue UniVersity,
West Lafayette, Indiana 47907, and the Institute for Molecular Science,
Myodaiji, Okazaki 444, Japan
ReceiVed NoVember 13, 1995X
Abstract: The reactions of internal and terminal alkynes with organoalanes containing Et, n-Pr, and i-Bu groups in
the presence of Cp2ZrCl2 and MeZrCp2Cl were investigated with the goal of clarifying mechanistic details of some
representative cases. Three fundamentally different processes, i.e., (i) C-M bond addition without C-H activation
in the alkyl group, (ii) cyclic C-M bond addition via C-H activation, and (iii) hydrometalation, have been observed,
and the courses of these reactions significantly depend on (i) the nature and number of alkyl groups in organoalanes,
(ii) their amounts, and (iii) solvents. The reaction of alkynes with Et3Al in the presence of 0.1 equiv of Cp2ZrCl2
in nonpolar solvents, e.g., hexanes, proceeds via C-H activation to give the corresponding aluminacyclopentenes.
Investigation of the reaction of 5-decyne with 1-3 equiv of Et3Al and 1 equiv of Cp2ZrCl2, which gave mono-, di-,
or trideuterated (Z)-5-ethyl-5-decene as shown in Scheme 10, together with the previously reported structural study
on the reaction of Et3Al with Cp2ZrCl2 leading to the formation of well-characterized bimetallic species 9, 10, and
11 (Scheme 11), supports a catalytic cycle involving bimetallic species 10 and 18 (Scheme 15). In summary, this
process requires a zirconocene derivative containing one Zr-bound Et group which is linked to Et3Al (but not to
Et2AlCl) through a Cl bridge, i.e., 18, to produce 10 via â C-H activation. In sharp contrast, the reaction of Et2-
AlCl-Cp2ZrCl2 as well as of (n-Pr)2AlCl-Cp2ZrCl2 does not involve any C-H activation processes. It proceeds
well in chlorinated hydrocarbon solvents, e.g., (CH2Cl)2, but it is extremely sluggish in nonpolar solvents, e.g.,
hexanes. The reaction may well involve direct C-Al bond addition to alkynes, as suggested earlier for Zr-catalyzed
Me-Al bond addition to alkynes, but a few other alternatives cannot be ruled out on the basis of the currently
available data. The reaction of alkynes with (n-Pr)3Al-Cp2ZrCl2 in nonpolar solvents proceeds partially via C-H
activation and partially via hydrometalation. In contrast with the C-H activation process observed with Et3Al, that
with (n-Pr)3Al is totally dominated by dimerization of alkynes to give aluminacyclopentadienes rather than
aluminacyclopentenes, reflecting a previously established generalization that propene can be much more readily
displaced from Zr by alkynes than ethylene. Hydrometalation is the exclusive process with (i-Bu)3Al-Cp2ZrCl2.
This hydrometalation reaction, however, reveals a few interesting complications. Alkyl-substituted internal alkynes
give double bond migrated products in addition to the expected hydrometalation products. With terminal alkynes
the reaction produces the expected hydrometalation products and the 1,1-dimetalloalkanes in comparable yields.
Various other related reactions involving other alkynes, e.g., PhCtCPh, n-OctCtCH, and PhCtCH, and other
reagents, e.g., Et3Al-MeZrCp2Cl, Et2AlCl-MeZrCp2Cl, and (n-Pr)3Al-MeZrCp2Cl, were also studied.
Introduction
In 1978 we reported the zirconium-catalyzed controlled
single-stage carboalumination of alkynes1 (eq 1) as well as its
titanium analogue2 (e.g., eq 2), the latter of which has turned
out to be only stoichiometric in titanium.3 We initially
envisioned that the Zr-catalyzed methylalumination of alkynes
might involve (i) methylation of Cp2ZrCl2 with Me3Al to
produce MeZrCp2Cl and Me2AlCl, (ii) methylzirconation of
alkynes to give the corresponding alkenylzirconium derivatives,
and (iii) their transmetalation with Me2AlCl to yield the observed
alkenyldimethylalanes with regeneration of Cp2ZrCl2 (Scheme
1). This proposed mechanism was primarily based on a
reversible Me-Cl exchange between Me3Al and Cp2ZrCl2
observed by NMR spectroscopy,4 and the stoichiometric reaction
of RCtCAlMe2 with MeZrCp2Cl shown in eq 3.5 However,
our later study has indicated that the reaction may involve direct
addition of the Me-Al bond to alkynes assisted by a ZrCp2
derivative4 (Scheme 2). Specifically, Me2AlCl-Cp2ZrCl2 is a
reasonable methylaluminating agent4 (eq 4), even though no
† Purdue University.
‡ Institute for Molecular Science.
§ Visiting Scholar, Purdue University (1994).
Current address: Catalysis Research Center, Hokkaido University,
Sapporo 060, Japan.
X Abstract published in AdVance ACS Abstracts, October 1, 1996.
(1) (a) Van Horn, D. E.; Negishi, E. J. Am. Chem. Soc. 1978, 100, 2252.
(b) Negishi, E.; Van Horn, D. E.; Yoshida, T. J. Am. Chem. Soc. 1985,
107, 6639. (c) Negishi, E. Pure Appl. Chem. 1981, 53, 2333.
(2) Van Horn, D. E.; Valente, L. F.; Idacavage, M. J.; Negishi, E. J.
Organomet. Chem. 1978, 156, C20.
(4) Negishi, E.; Yoshida, T. J. Am. Chem. Soc. 1981, 103, 4985.
(5) Yoshida, T.; Negishi, E. J. Am. Chem. Soc. 1981, 103, 1276.
(3) Unpublished results by Kondakov, D. Y. and Negishi, E.
S0002-7863(95)03803-0 CCC: $12.00 © 1996 American Chemical Society

9578 J. Am. Chem. Soc., Vol. 118, No. 40, 1996
Negishi et al.
Scheme 1
Scheme 5
Scheme 6
Scheme 2
(Scheme 4). Although the authors initially reported tris(2-
ethylalkyl)alanes as the products,9a they later found that the
reaction yielded 3-substituted aluminacyclopentanes.10 In 1991
we11 clarified the mechanism of the Dzhemilev’s ethylmagne-
siation reaction (Scheme 5), and our conclusion has been further
supported by concurrent and subsequent related studies.12 In
summary, Zr-catalyzed reactions of organoalanes with alkenes
and alkynes may proceed by (i) direct C-M bond addition
without the formation of cyclic intermediates, (ii) C-M bond
additions involving metallacyclic intermediates, and (iii) hy-
drometalation.
Scheme 3
The contrasting reaction courses and mechanisms presented
above are not solely attributable to the difference in the alkyl
groups, i.e., Me, Et, and i-Bu, since even organoalanes contain-
ing the same alkyl group can undergo two or more distinct
reactions. For example, we have reported that the reaction of
R2AlCl-Cp2ZrCl2, where R ) Et, n-Pr, and higher n-alkyls,
with alkynes gives the corresponding alkylaluminated products,
for which a process similar to that shown in Scheme 2 has been
proposed.4 In 1992 Dzhemilev13 reported that the corresponding
reaction of Et3Al-Cp2ZrCl2 gave aluminacyclopentene deriva-
tives. In fact, a similar enyne bicyclization reaction with Et3-
Al-Cp2ZrCl2 had also been observed by us14 a few years before
the Dzhemilev’s publication. The dichotomous behavior shown
in Scheme 6 as well as those diverse results reported earlier
prompted us to systematically investigate various reactions of
alkynes and alkenes with organoaluminums and zirconocene
derivatives. Herein we discuss those results obtained with
alkynes with emphasis on various reaction parameters governing
strikingly multimechanistic aspects of these reactions. We
Scheme 4
Me-Cl exchange to produce MeZrCp2Cl is detectable by NMR
spectroscopy. However, rigorous exclusion of the mechanism
shown in Scheme 1 cannot be made on the basis of the available
data.
(8) For Zr-catalyzed methylalumination of alkenes catalyzed by chiral
zirconocene derivatives, see: Kondakov, D. Y.; Negishi, E. J. Am. Chem.
Soc. 1995, 117, 10771. See also Kondakov, D. Y.; Negishi, E. J. Am. Chem.
Soc. 1996, 118, 1577.
(9) (a) Dzhemilev, U. M.; Ibragimov, A. G.; Vostrikova, O. S.; Tolstikov,
G. A. IzV. Akad. Nauk SSSR, Ser. Khim. 1985, 207. (b) Dzhemilev, U. M.;
Ibragimov, A. G.; Vostrikova, O. S.; Tolstikov, G. A. IzV. Akad. Nauk SSSR,
Ser. Khim. 1989, 196. (c) Dzhemilev, U. M.; Ibragimov, A. G.; Zoloterev,
A. P.; Tolstikov, G. A. IzV. Akad. Nauk SSSR, Ser. Khim. 1989, 1324.
(10) Dzhemilev, U. M.; Ibragimov, A. G.; Zolotarev, A. P.; Muslukhov,
R. R.; Tolstikov, G. A. IzV. Akad. Nauk SSSR, Ser. Khim. 1991, 2570.
(11) Takahashi, T.; Seki, T.; Nitto, Y.; Saburai, M.; Rousset, C. J.;
Negishi, E. J. Am. Chem. Soc. 1991, 113, 6266.
(12) (a) Knight, K. S.; Waymouth, R. M. J. Am. Chem. Soc. 1991, 113,
6268. (b) Hoveyda, A. H.; Xu, Z. J. Am. Chem. Soc. 1991, 113, 5079. (c)
Lewis, D. P.; Muller, D. M.; Whitby, R. J.; Jones, R. V. H. Tetrahedron
Lett. 1991, 32, 6797.
(13) Dzhemilev, U. M.; Ibragimov, A. G.; Zolotarev, A. P. MendeleeV
Commun. 1992, 135.
In contrast with Me3Al-Cp2ZrCl2, i-Bu3Al-Cp2ZrCl2 would
hydroaluminate alkynes as well as alkenes, for which a
transmetalation-hydrozirconation-back transmetalation mech-
anism shown in Scheme 3 was proposed.6
Our initial attempts to observe Zr-catalyzed carboalumination
of alkenes did not yield the desired products in detectable yields
(vide infra). Several years later, Dzhemilev7 reported Zr-
catalyzed ethylmagnesiation of monosubstituted alkenes (Scheme
4). Methylmagnesium derivatives did not participate in this
reaction.8 A related reaction of Et3Al with monosubstituted
alkenes catalyzed by ZrCp2 derivatives was also reported9
(6) Negishi, E.; Yoshida, T. Tetrahedron Lett. 1980, 1501.
(7) Dzhemilev, U. M.; Vostrikova, O. S.; Sultanov, R. M. IzV. Akad.
Nauk SSSR, Ser. Khim. 1983, 218.
(14) Observed in 1990 by Swanson, D. R. Work along this line is in
progress with Choueiry, D. and Kondakov, D. Y.

Zirconium-Catalyzed Carboalumination of Alkynes
J. Am. Chem. Soc., Vol. 118, No. 40, 1996 9579
Scheme 7
Scheme 8
Scheme 9
further focus our attention on elucidation of factors critically
responsible for those C-M bond addition reactions involving
C-H activation to produce metallacyclic intermediates.
Results and Discussion
With the goal of further exploring the synthetic scope and
probing mechanistic details of alkylmetalation other than
methylmetalation1 of alkynes with alkylalanes catalyzed or
promoted by zirconocene derivatives, various reactions involving
the following reagents were investigated: alkynes, internal
alkynes (5-decyne, 3-hexyne, and diphenylethyne) and terminal
alkynes (1-octyne, 1-decyne, 1-dodecyne, and phenylethyne);
organoalanes,15 R3Al and R2AlCl, where R ) Et, n-Pr, and i-Bu;
zirconocene derivatives, Cp2ZrCl2 and MeZrCp2Cl; and solvents,
hexanes, benzene, CH2Cl2, and (CH2Cl)2.
Scheme 10
Trialkylalanes, i.e., Et3Al, (n-Pr)3Al, and (i-Bu)3Al, and Et2-
AlCl, as well as Cp2ZrCl2, were purchased from commercial
sources. Di(n-propyl)aluminum chloride was prepared in situ
by mixing (n-Pr)3Al and AlCl3 in a 2:1 molar ratio, respectively,
according to the literature.16 Conversion of Cp2ZrCl2 to
O(ZrCp2Cl)2 followed by the treatment of the latter with Me3-
Al according to the literature17 provided MeZrCp2Cl.
Scheme 11
Reactions of Alkynes with Ethylalanes and Zirconocene
Derivatives. (a) Results of Representative Reactions of
5-Decyne with Et3Al in the Presence of a Catalytic Amount
of Cp2ZrCl2. The reaction of 5-decyne with Et3Al (3 equiv)
and 0.1 equiv of Cp2ZrCl2 in (CH2Cl)2 at 23 °C, following the
typical conditions for the Zr-catalyzed methylalumination,1
produced, after deuterolysis with DCl-D2O, mono- and/or
dideuterated 1-3 in the yields indicated in Scheme 7. It should
be noted that the extent of D incorporation in the Et group of
1 was only 50%. The use of hexanes in place of (CH2Cl)2 not
only accelerated the reaction but also led to a cleaner product.
Thus, the reaction was over within 6 h at 23 °C, and the product
obtained in 92% yield after deuterolysis as above was 1 in which
the extents of D incorporation were >98% at both positions.
Treatment of the reaction mixture provided the expected
diiodinated product 4 in 54% yield. These results support the
assignment of an aluminacyclopentene derivative 5 to the
product, as in the previous report,13 although other cyclooligo-
meric and polymeric structures may be present (Vide infra)
(Scheme 8).
a zirconacyclopentene 6 is generated as a crucial intermediate
(Scheme 9), even though there was no spectroscopic indication
for the formation of Cp2ZrEt2 by the reaction of Et3Al and Cp2-
ZrCl2 in a 1:1 molar ratio. Both the formation of (ethylene)-
zirconocene18 and its ring expansion to give 619 were known.
To our surprise, however, no desired reaction was observed at
a significant rate when 0.2 equiv of 6 preformed by the reaction
of Cp2ZrEt2 with 5-decyne18 was added to a mixture of 5-decyne
and Et3Al (1.2 equiv). The results ruled out the intermediacy
of 6 and hence the mechanism shown in Scheme 9.
(b) Initially Proposed but Untenable Mechanism via
Double Trasmetalation. We initially assumed that the cy-
cloalumination reaction shown in Scheme 8 would proceed in
a manner similar to Dzhemilev’s Zr-catalyzed ethylmagnesiation
of alkenes11 (Scheme 5). On this basis, we envisioned a
mechanism involving reversible double transmetalation in which
(c) Results of Representative Reactions of 5-Decyne with
Et3Al in the Presence of the Stoichiometric Amount of
Cp2ZrCl2. Highly informative from the viewpoint of mecha-
nistic clarification were the results of the reaction of 5-decyne
(15) Organoalanes generally exist as dimers. For the sake of simplicity,
however, monomeric structures are used unless the use of dimeric structures
is considered to be essential.
(16) Mole, T.; Jeffery, E. A. Organoaluminum Compounds, Elsevier,
Amsterdam, 1972; p 465.
(18) (a) Negishi, E.; Nguyen, T.; Maye, J. P.; Choueiry, D.; Suzuki, N.;
Takahashi, T. Chem. Lett. 1992, 2367. (b) For a review, see: Negishi, E.;
Takahashi, T. Acc. Chem. Res. 1994, 27, 124. See also Buchwald, S. L.;
Nielsen, R. B. Chem. ReV. 1988, 88, 1047.
(19) Takahashi, T.; Kageyama, M.; Denisov, V.; Hara, R.; Negishi, E.
Tetrahedron Lett. 1993, 34, 687.
(17) Surtees, J. R. J. Chem. Soc., Chem. Commun. 1965, 567.

9580 J. Am. Chem. Soc., Vol. 118, No. 40, 1996
Negishi et al.
Scheme 12
with Et3Al (1-3 equiv) in the presence of the stoichiometric
amount of Cp2ZrCl2. As summarized in Scheme 10, three
discrete carbometalation products, i.e., 1, 7, and 8, were obtained
after deuterolysis under three slightly different conditions.
Specifically, 1 is the predominant product (84%), when 5-de-
cyne, Et3Al (3 equiv), and Cp2ZrCl2 (1 equiv) were mixed all
at once in benzene. In sharp contrast, when only 1 equiv of
Et3Al was used, the major product obtained in 65% yield was
(Z)-5-ethyl-6-deuterio-5-decene (7). Interestingly, when 3 equiv
of Et3Al was allowed to react with 1 equiv of Cp2ZrCl2 for 24
h before addition of 5-decyne, (Z)-5-(2′,2′-dideuterioethyl)-6-
deuterio-5-decene (8) was obtained as the major product in 87%
yield. Clearly, three discrete, if related, processes must take
place under the indicated conditions.
(d) Previously Known Results of the Reaction of Et3Al
with Cp2ZrCl2 in the Absence of Alkynes. A series of detailed
investigations of the reaction of Et3Al with Cp2ZrCl2 using NMR
spectroscopy and X-ray analysis by Sinn20,21 and Kaminsky21
has proved to be highly relevant. These workers have reported
that the reaction of Cp2ZrCl2 with Et3Al in C6D6 rapidly
produces a mixture of 9a and 9b, which is relatively stable when
only 1 equiv of Et3Al is used. With an excess of Et3Al,
however, a C-H activation process takes place to give a
relatively unstable species 10 which is subsequently converted
to a more stable product 11 via the second C-H activation
process along with a smaller amount of 12. The X-ray structures
of 11 and 12 have also been reported.21c We have confirmed
these results mainly with NMR spectroscopy.
likely proceeds via direct ethylmetalation of 5-decyne with 9.
Judging from the extents of D incorporation, 1 and 8 must be
formed via the reactions of 5-decyne with 10 and 11, respec-
tively. Among several possible alternatives we favor the four-
centered carbozirconation process proceeding via 13 and 14,
respectively. This process should provide 15 and 16, respec-
tively, as the initial carbometalation products which may
undergo subsequent transformations (vide infra). Similar modes
of activation of C-Zr bonds via polarization by ring opening
have been proposed for carbometalation of alkenes.22 Further-
more, the regiochemistry of D incorporation in 8 is compatible
with the proposed carbozirconation but incompatible with
carboalumination, which would produce the 1,2-dideuterioethyl-
containing isomer of 8. By analogy, we favor the proposed
carbozirconation process producing 15 as the initial product over
a carboalumination process which would initially give 17. Of
these three stoichiometric processes, however, only the process
involving the formation of 10 and its reaction with 5-decyne to
give 1 upon deuterolysis are relevant to the catalytic process,
since neither 7 nor 8 was formed in the catalytic reaction shown
in Scheme 8.
(f) Mechanistic Interpretation of the Formation of 10 via
Bimetallic â C-H Activation and Its Reaction with 5-Decyne
Under Stoichiometric Conditions. The formation of 10 by
the reaction of 9 with Et3Al requires a â C-H activation process.
Addition of an excess of ClAlEt2 to 9 does not induce the desired
C-H activation to produce 10. Evidently, this process requires
the second equivalent of Et3Al. We propose that Et3Al displaces
ClAlEt2 in an unfavorable equilibrium and that the EtZrCp2-
Cl-AlEt3 complex 18 thus formed undergoes a bimetallic â
C-H activation reaction, most probably triggered by â agostic
interaction of the EtZrCp2 moiety, to give 10, as depicted in
Scheme 13. An extra equivalent of Et3Al rather than ClAlEt2
is necessary probably because ClAlEt2 forms a relatively stable
complex 9 which can exist as a doubly chlorine-bridged species
9b and is hence less prone to give an open and hence activated
species corresponding to 18. Et3Al should also be more basic
and hence better able to abstract H than ClAlEt2. To further
(e) Correlation between the Stoichiometric Processes
Shown in Schemes 10 and 11. Comparison of the results
shown in Schemes 10 and 11 suggested to us that there must
be 1:1 correspondences between the three reactions in Scheme
10 and those in Scheme 11 as shown in Scheme 12. Since the
formation of 7 does not incorporate D in the Et group, it most
(20) (a) Sinn, H.; Oppermann, G. Angew. Chem., Int. Ed. Engl. 1966, 5,
962. (b) Sinn, H.; Kolk, E. J. Organomet. Chem. 1966, 6, 373.
(21) (a) Kaminsky, W.; Sinn, H. Liebigs Ann. Chem. 1975, 424. (b)
Kaminsky, W.; Vollmer, H. J. Liebigs Ann. Chem. 1975, 438. (c) Kaminsky,
W.; Kopf, J.; Sinn, H.; Vollmer, H. J. Angew., Chem., Int. Ed. Engl. 1976,
15, 629.
(22) Erker, G.; Noe, R.; Wingbermu¨hle, D. Chem. Ber. 1994, 127, 805.

Zirconium-Catalyzed Carboalumination of Alkynes
J. Am. Chem. Soc., Vol. 118, No. 40, 1996 9581
Scheme 13
Scheme 14
support the mechanism shown in Scheme 13, an Al-free sample
of EtZrCp2Cl was generated by hydrozirconation of ethylene
with HZrCp2Cl in C6D6 in 90% NMR yield and then treated
with 1 equiv of Et3Al at 23 °C. This reaction cleanly produced
within 30 min an 83% yield of 10. In contrast, the reaction of
Cp2ZrCl2 with two or more equivalents of Et3Al was much
slower, and is complicated by side reactions. The major
difference in these two reactions may be attributable to the
absence of ClAlEt2 in the former and its presence in the latter
in which Et3Al must displace in situ generated ClAlEt2.
(g) Mechanism of the Catalytic Reaction of 5-Decyne with
an Excess of Et3Al in the Presence of Cp2ZrCl2. The
observed results and interpretations of the stoichiometric reac-
tions shown in Schemes 13 and 14 combine to point to the
mechanism shown in Scheme 15 for the Cp2ZrCl2-catalyzed
reaction of 5-decyne with an excess of Et3Al. In this scheme,
the catalytic process is initiated by the reaction of Cp2ZrCl2
with two or more equivalents of Et3Al to produce 10 via
bimetallic â C-H activation (Scheme 13). This bimetallic
reagent then undergoes carbozirconation with 5-decyne to give
EtZrCp2Cl and 5, most probably via 13, 15, and 19 (Schemes
12 and 14). EtZrCp2Cl thus generated reacts with Et3Al to
regenerate 10 via 18 (Scheme 13) to complete a catalytic cycle.
The crucial bimetallic â C-H activation proces depicted in 18
requires (i) a coordinatively unsaturated EtZrCp2 moiety capable
of exhibiting â C-H agostic interaction, (ii) the second
equivalent of Et3Al, and (iii) one Cl atom to bind Zr and Al via
a Zr-Cl-Al bond. The requirement for the second equivalent
of Et3Al or an equivalent trialkylalane has been experimentally
demonstrated under both stoichiometric and catalytic conditions.
To further substantiate the need for one Cl atom, the following
comparative experiments were carried out. As stated earlier, a
zirconacyclopentene 6 did not induce the cyclic carboalumina-
tion of 5-decyne with Et3Al. However, addition of Et2AlCl to
the reaction mixture did generate an active catalyst for the
desired reaction. Similarly, the reaction of 5-decyne with 1
equiv of Et3Al and 0.2 equiv of (n-Bu)2ZrCp2, generated from
Cp2ZrCl2 and 2 equiv of n-BuLi23 in toluene and added as a
source of “ZrCp2”, produced, on hydrolysis, only traces (<5%)
of (Z)-5-ethyl-5-decene along with (E,E)-6,7-di(n-butyl)-5,7-
dodecadiene formed as the major product (20%). In this
reaction, all Cl atoms are sequestered in the form of LiCl. In
sharp contrast, addition of 0.2 equiv of Et2AlCl to the same
reaction mixture at the beginning of the reaction followed by
protonolysis led to a 73% yield of (Z)-5-ethyl-5-decene along
with a minor amount (14%) of the conjugated diene. On
deuterolysis, 1 was obtained in a comparable yield. These
results indicate that alkene-zirconocenes alone do not serve as
catalysts for cyclic carboalumination of alkynes with Al-Zr
Analysis of 10 prepared by the reaction of EtZrCp2Cl and
Et3Al by 1H (500 MHz) and 13C (75.4 MHz) NMR spectroscopy
including COSY and HETCOR techniques led to the signal
assignments shown in Scheme 13. Although the 1H NMR
signals were previously reported,20 there exists a significant
discrepancy between the chemical shift value of δ 1.45-1.5
ppm assigned by us to a multiplet attributable to the Zr-bound
CH2 group and the previously assigned shift value of δ 0.7
ppm.20 We presume that the use of a low-field frequency in
the previous study must have led to an erroneous assignment.
The 13C NMR data have not been previously reported.
As expected, the reaction of 10 with 1 equiv of 5-decyne
proceeded smoothly in C6D6 at 23 °C and was fast and complete
in 10 min to give EtZrCp2Cl and 5. This reaction is much faster
than either the catalytic reaction shown in Scheme 8 or the
stoichiometric reaction producing 1 on deuterolysis shown in
Scheme 10. Here again, the difference may be attributable to
the inhibitory effect of in situ generated Et2AlCl on the
formation of 10 in the latter two reactions. The formation of
EtZrCp2Cl was readily indicated by the 1H and 13C NMR signals
at δ 5.78 ( 0.04 and 112.60 ( 0.35, respectively, for the Cp
group of EtZrCp2Cl regardless of whether or not Et2AlCl and/
or Et3Al were additionally present. Consequently, they did not
provide accurate information about the interactions between
EtZrCp2Cl and organoalanes. These signals were also very
insensitive to various solvents such as THF, provided that C6D6
was used as an NMR solvent. Luckily, we found that the 13C
NMR signal for the Zr-bound CH2 of Et was very sensitive to
the presence or absence of an additional organoalane, even
though it was still insensitive to THF. Specifically, it appeared
at δ 46.5 ( 0.16 in the absence of Et2AlCl, but it shifted
downfield (δ 49-54) in the presence of Et2AlCl. Analysis of
this signal also indicated that there was little, if any, interaction
between EtZrCp2Cl and the alkyne-inserted organoaluminum
product, although this point should be further clarified. The
organoaluminum product showed as before a relatively complex
set of signals, but it was cleanly converted to 1 upon deuteroly-
sis. We suggest that the stoichiometric reaction of 5-decyne
with 10 to give EtZrCp2Cl and 5 proceeds via 15 and 19 as
shown in Scheme 14. Conversion of 15 into 19 merely requires
Et-vinyl exchange, which should be kinetically facile, and 19
must prefer to exist as a mixture of EtZrCp2Cl and 5.
(23) (a) Negishi, E.; Cederbaum, F. E.; Takahashi, T. Tetrahedron Lett.
1986, 27, 2829. (b) Negishi, E.; Holmes, S. J.; Tour, J. M.; Miller, J. A.;
Cederbaum, F. E.; Swanson, D. R.; Takahashi, T. J. Am. Chem. Soc. 1989,
111, 3336.

9582 J. Am. Chem. Soc., Vol. 118, No. 40, 1996
Negishi et al.
Scheme 15
AlCl-Cp2ZrCl2 reagent system lacking Et3Al is incapable of
inducing cyclic carboalumination of alkynes via C-H activation.
This reaction is also sensitive to the nature of solvents. Thus,
treatment of 5-decyne with 1 equiv of Et2AlCl in the presence
of either 0.1 or 1 equiv of Cp2ZrCl2 in hexanes at 23 °C did
not induce any reaction over at least 1 day, with g90-95% of
the starting materials remaining unchanged. In sharp contrast,
the same reaction run in (CH2Cl)2 at 23 °C using either 0.1 or
1 equiv of Cp2ZrCl2 proceeded smoothly to give, after treatment
with DCl-D2O, a 90% yield of 7, in which the extent of D
incorporation was g95%. Zirconocene dichloride was regener-
ated to the extent of g95%. The observed solvent effects are
analogous to those observed in the methylalumination reaction
with Me3Al-Cp2ZrCl2,1,4 suggesting that significant bond
polarization occurs in the transition state, which must be
essential to the observed reaction. Examination of a 1:1 mixture
of Et2AlCl and Cp2ZrCl2 by NMR spectroscopy indicates that
no Et transfer from Al to Zr occurs beyond the detection limit
of 0.1%. It should also be noted that both stoichiometric and
catalytic reactions with Et2AlCl and Cp2ZrCl2 produce the same
products including regenerated Cp2ZrCl2 most probably via the
same mechanism. As in the case of the Zr-catalyzed methy-
lalumination, we are inclined to propose direct C-Al bond
addition mechanisms similar to that shown in Scheme 2
(designated as 4-C-Al).25 However, other mechanisms such as
that involving direct C-Zr bond addition similar to the one
shown in Scheme 1 (4-C-Zr)25 and even some six-centered
processes represented by 20 (6-C-Zr)25 and 21 (6-C-Al)25 cannot
be rigorously ruled out on the basis of the currently available
data. Despite mechanistic ambiguities, the highly contrasting
features of this reaction and its cyclic analogue as well as its
synthetic value should be clearly noted.
Scheme 16
reagent systems but that introduction of Cl converts them to
active catalysts. It is very likely that Et2AlCl converts (ethyl-
ene)zirconocene into 10 as shown in Scheme 13.
(h) Comparison of r and â C-H Activation Processes of
Zirconocenes and Titanocenes. It is worth mentioning here
that the C-H activation process depicted in 18 in Scheme 13
and the catalytic process and principle involving 10 and 18
shown in Scheme 15 represent novel modes of C-H activation
and catalysis, although some related but different processes such
as (i) â C-H activation of dialkylzirconocenes18 and its
involvement in the Zr-catalyzed carbomagnesiation reaction11,21b
and (ii) R C-H activation processes involving Al and Ti
compounds24 are known. In this connection, it is instructive to
compare some salient features of these related processes, which
are summarized in Scheme 16. In contrast with the Zr-catalyzed
carbomagnesiation of alkenes7,11,12 proceeding via monometallic
C-H activation, the mode of C-H activation shown in 18 is
bimetallic. Whereas the former requires double alkylation of
zirconium, the latter proceeds via single alkyl transfer. The
three crucial requirements for the Al-Zr bimetallic â C-H
activation process are as discussed above. In these respects,
the Al-Zr reaction might more closely resemble the formation
of the Tebbe reagent24 from Cp2TiCl2 and Me3Al. However,
this Al-Ti reaction involves R C-H activation. Furthermore,
to the best of our knowledge, essentially all known reactions
of the Tebbe reagents appear to be only stoichiometric. On
the other hand, both of the â C-H activation processes of
organozirconiums can be crucial steps in catalytic processes.
(i) Reaction of 5-Decyne with Et2AlCl-Cp2ZrCl2. Re-
markable Solvent Effects. As indicated in Scheme 6, the Et2-
(j) Synthetic Scope of Ethylalumination of Alkynes in the
Presence of Cp2ZrCl2. We have also studied the stoichiometric
reactions of 5-decyne with (i) Et3Al-MeZrCp2Cl and (ii) Et2-
AlCl-MeZrCp2Cl. The reaction of 5-decyne with 1 equiv each
of Et3Al and MeZrCp2Cl17 in hexanes at 23 °C for 2 h provided,
after deuterolysis, 1 in 67% yield with g90% D incorporation
at either position along with the dimer 3a (g90% D) obtained
in 20% yield. The same reaction in (CH2Cl)2 required 12-14
h at 23 °C for completion, and the products consisted of 1 (69%)
and 3a (e9%). These results clearly point to a C-H activation
process similar to that shown in Scheme 13. We earlier used
the same Et3Al-MeZrCp2Cl system and concluded that the
exclusive incorporation of Et rather than Me was an indication
of direct C-Al bond addition.4 This was clearly incorrect and
must therefore be corrected. Interestingly, the reaction of
5-decyne with Et2AlCl (3 equiv) and MeZrCp2Cl (1 equiv) in
(CH2Cl)2 cleanly produced, after deuterolysis, the monodeu-
terated alkene 7 in 93% yield. The extent of D incorporation
at the alkenyl position was g91%. No D incorporation in the
Et group was observed. Curiously, the amount of (Z)-5-methyl-
5-decene was negligible, even though a mixture of Et2AlCl and
MeZrCp2Cl undergoes Me-Et exchange. The courses of the
Zr-catalyzed ethylalumination of various alkynes including those
(24) (a) Tebbe, F. N.; Parshall, G. W.; Reddy, G. S. J. Am. Chem. Soc.
1978, 100, 3611. (b) Brown-Wensley, K. A.; Buchwald, S. L.; Cannizzo,
L.; Clawson, L.; Ho, S.; Meinhardt, D.; Stille, J. R.; Straus, D.; Grubbs, R.
H. Pure Appl. Chem. 1983, 55, 1733. (c) Ott, K. C.; deBoer, E. J. M.;
Grubbs, R. H. Organometallics 1984, 3, 223.
(25) In this designation, the first number indicates the number of
participating atoms, and C-Al and C-Zr indicate addition of C-Al and
C-Zr bonds to alkynes, respectively.

Zirconium-Catalyzed Carboalumination of Alkynes
J. Am. Chem. Soc., Vol. 118, No. 40, 1996 9583
Table 1. Reaction of Alkynes with Et3Al and Et2AlCl in the Presence of 10 mol % of Cp2ZrCl2
a By NMR spectroscopy or GLC. b Not detected or determined. c See Scheme 7 for information on the products.
observed with 5-decyne are summarized in Table 1. These
results permit the following generalizations. First, the courses
of the reactions of various other alkynes are similar to those
observed with 5-decyne. Specifically, the reaction with Et3Al
involves largely the C-H activation process leading to the
formation of dideuterated products via deuterolysis. On the
other hand, the reaction with Et2AlCl leads to the formation of
monodeuterated products. Second, two possible regioisomers
are obtained from terminal alkynes, although all of the reactions
proceed without producing stereoisomers to any detectable
Scheme 17
2
extents. The extent of D incorporation at the Csp center is
uniformly high (>90%), while that in the Me group of the Et
substituent varies. With Et2AlCl as the carbometallating agent,
no D incorporation in the Et substituent is observed. In the
reactions of terminal alkynes with Et3Al, the extent of D
incorporation in the Et substituent of the 1,2-disubstituted
alkenes is >90%, indicating that these products are obtained
via the C-H activation process. On the other hand, the extent
of D incorporation in the Et substituent of the 1,1-disubstituted
alkenes has been in the 40-60% range, suggesting that roughly
half of these products stem from the C-H activation process.
This represents a deviation from the course of the reaction of
internal alkynes.
Reactions of Alkynes with n-Propyl- and Isobutylalanes
and Zirconocene Derivatives. The reaction of 5-decyne with
either (n-Pr)3Al or (n-Pr)2AlCl in the presence of 0.1 equiv of
either Cp2ZrCl2 or MeZrCp2Cl was carried out in hexanes,
toluene, or (CH2Cl)2, and the results summarized in Table 2
indicate that the course of the reaction significantly depends
on the structure of the n-propylalane reagent and the solvent.
In addition to alkyl-metal bond addition and C-H activation
processes, hydrometalation can be a dominant process with
n-propylalanes. Specifically, the reaction of 5-decyne with (n-
Pr)3Al in hexanes with either Cp2ZrCl2 or MeZrCp2Cl as a
catalyst did not yield the expected n-propylmetalation product
22 in more than trace quantities, if any. The major products
were a mixture of 23a and 23b (∼65% combined yield) and a
dimer 24 (30-40% based on 5-decyne) (Scheme 17). The
hydroalumination products were stereoisomerically >98% pure.
On deuterolysis of the reaction mixtures, 2, (Z)-5-deuterio-4-
decene (25), and 3a were obtained. The extents of D incorpora-
tion were all g90-95%. Although 25 was regioisomerically
pure (>98%), its regiochemistry was not readily determined
on the basis of its NMR spectra. However, the corresponding
reaction of 3-hexyne gave, after deuterolysis, a mixture of 26

9584 J. Am. Chem. Soc., Vol. 118, No. 40, 1996
Negishi et al.
Table 2. Reaction of 5-Decyne with (n-Pr)3Al or (n-Pr)2AlCl in the Presence of 10 mol % of Cp2ZrCl2 or MeZrCp2Cl
a By GLC or NMR spectroscopy and based on the starting alkyne. b Not observed.
Scheme 18
Scheme 19
and Et2AlCl-Cp2ZrCl2, this reaction may involve direct C-Al
bond addition assisted by Zr either via 4-C-Al or the 6-C-Zr
process. In accord with the other cases, the reaction was very
sluggish in nonpolar solvents, such as hexanes.
and 27 along with 28, and the regiochemistry of 27 was
unequivocally assigned by NMR spectroscopy. The formation
of 25 and 27 and the regioselective D incorporation are
consistent with the hydrometalation-dehydrometalation mech-
anism shown in Scheme 18 for the reaction of 5-decyne, which
involves exclusive attachment of Zr to the central carbon atom
of an allene.26 Both predominant hydrometalation and alkyne
dimerization are attributable to the use of (n-Pr)3Al in place of
Et3Al. Evidently, n-PrZrCp2Cl generated in situ from (n-Pr)3Al
and Cp2ZrCl2 is a more efficient hydrometalating agent than
the corresponding Et derivative. It has been amply demonstrated
that, whereas (ethylene)zirconocene can react with alkynes to
produce zirconacyclopentenes, (1-butene)zirconocene gives
predominantly or exclusively zirconacyclopentadienes.23 (Pro-
pene)zirconocene containing a monosubstituted alkene must
react more like (1-butene)zirconocene than (ethylene)zir-
conocene. The course of the reaction observed with (n-Pr)3Al-
MeZrCp2Cl is very similar to that observed with (n-Pr)3Al-
Cp2ZrCl2. Here again, the absence of methylmetalation products
remains as a puzzle to be clarified.
The reaction of PhCtCPh, n-OctCtCH, and PhCtCH with
3 equiv of (n-Pr)3Al and 0.1 equiv of Cp2ZrCl2 in hexanes or
toluene was also briefly studied. The reaction of PhCtCPh in
toluene gave, after protonolysis, a 3:2 mixture of (E)- and (Z)-
stilbene in 68% yield along with (E,E)-1,2,3,4-tetraphenyl-1,3-
butadiene (24% based on PhCtCPh). The reaction of
n-OctCtCH and PhCtCH gave, after protonolysis, the corre-
sponding alkenes in 61 and 53% yields, respectively, along with
minor amounts of the doubly hydrometalated products.
In view of our recent report on the hydrozirconation of
alkynes with i-BuZrCp2Cl generated in situ from t-BuMgCl and
Cp2ZrCl2 in ether,27 similar results might be expected from (i-
Bu)3Al-Cp2ZrCl2. Indeed, the reaction of 5-decyne and
1-decyne with 3 equiv of (i-Bu)3Al and 0.1 equiv of Cp2ZrCl2
was totally dominated by hydrometalation with no indication
of carbometalation with a couple of notable but expected
deviations from the course of the corresponding reaction with
t-BuMgCl-Cp2ZrCl2. Thus, the reaction of 5-decyne gave, after
deuterolysis, an essentially 1:1 mixture of 2 and 25 in 87%
overall yield, while that of 1-decyne produced an essentially
1:1 mixture of (E)-1-deuterio-1-decene and 1,1-dideuteriodecane
in quantitative combined yield (Scheme 19).
As expected, the reaction of 5-decyne with 3 equiv of (n-
Pr)2AlCl and 0.1 equiv of Cp2ZrCl2 in (CH2Cl)2 produced the
n-propylmetalation product 22 in 75% yield, the amounts of
other monomeric and oligomeric products <5% each. Exami-
nation of a 1:1 mixture of (n-Pr)2AlCl and Cp2ZrCl2 in (CH2-
Cl)2 by NMR spectroscopy failed to reveal n-Pr-Cl exchange.
Conclusions
Various aspects of the reactions of internal and terminal
alkynes with organoalanes containing Et, n-Pr, and i-Bu groups
4
We suggest that, as in the reactions of Me2AlCl-Cp2ZrCl2
(26) Attachment of metals to the central carbon atom of allenes to varying
degrees has been observed in hydroboration. [For a review, see: Zaidlewicz,
M. In ComprehensiVe Organometallic Chemistry; Wilkinson, G., Stone, F.
G. A., Abel, E. W., Eds. Pergamon Press: Oxford, 1980; Vol. 7, pp 217-
218.] On the other hand, exclusive attachment of metals to the terminal
carbon atoms of allenes has been observed in carbopalladation. [Ahmar,
M.; Cazes, B.; Gore´, J. Tetrahedron Lett. 1984, 25, 4505.]
(27) Swanson, D. R.; Nguyen, T.; Noda, Y.; Negishi, E. J. Org. Chem.
1991, 56, 2590.
(28) An authentic sample of 2-ethyl-1-decene was prepared by the Wittig
methylenation of 3-undecanone. For the Wittig methylenation of alkenes,
see: Wittig, G.; Schoellkopf, U. Organic Syntheses; Wiley: New York,
1973; Collect. Vol. 5, p 751.
(29) Zweifel, G.; Steele, R. B. J. Am. Chem. Soc. 1967, 89, 5085.

Zirconium-Catalyzed Carboalumination of Alkynes
J. Am. Chem. Soc., Vol. 118, No. 40, 1996 9585
decene along with 2 (>95% D), 3a (>90% D), and (E,E)-6-(n-butyl)-
5,8-dideuterio-9-ethyl-7-(n-propyl)-5,7-tridecadiene (3b): 1H NMR
(CDCl3, Me4Si) δ 0.75-1.05 (m, 15 H), 1.05-1.55 (m, 16 H), 1.85-
2.15 (m, 8 H), 2.75-2.9 (m, 1 H); 13C NMR (CDCl3, Me4Si) δ 13.06,
14.06 (3 C), 14.28, 20.81, 22.49, 23.14, 23.22, 27.43, 29.30, 29.54,
30.16, 30.75, 31.88, 32.45, 37.29, 44.14, 123.76 (t, J ) 23 Hz), 127.45
(t, J ) 23 Hz), 140.35, 142.69; g80% D at C-5 and g88% D at C-8
by 13C NMR.
in the presence of Cp2ZrCl2 and MeZrCp2Cl were elucidated.
Some of the noteworthy conclusions are as follows.
1. These reactions may involve one or more of at least three
fundamentally different processes, i.e., (i) C-M bond addition
without involving C-H activation, (ii) C-H activation, and (iii)
the hydrometalation, and the courses of these reactions signifi-
cantly depend on (i) the nature and number of alkyl groups in
organoalanes, (ii) their amounts, and (iii) solvents.
2. Exclusive or nearly exclusive carbometalation without
involving C-H activation is observed with Et2AlCl or (n-
Pr)2AlCl in the presence of 0.1 equiv of Cp2ZrCl2 in polar
solvents, e.g., (CH2Cl)2. We tentatively suggest that these
reactions involve direct carboalumination via either 4-C-Al or
6-C-Zr process, but others via 4-C-Zr and 6-C-Al processes
cannot be rigorously ruled out.
3. Exclusive or nearly exclusive C-H activation is observed
with Et3Al and 0.1 equiv of Cp2ZrCl2 in nonpolar solvents, e.g.,
hexanes. A catalytic cycle involving bimetallic species 10 and
18 shown in Scheme 15 accommodates the observed results.
Generation of 10, which acts as an active carbometalating agent,
requires 18, which contains (i) a coordinatively unsaturated
alkylzirconocene moiety containing the â C-H bond, (ii) one
Cl atom, and (iii) Et3Al.
4. Exclusive hydrometalation is observed with (i-Bu)3Al-
Cp2ZrCl2. This process, however, is complicated by double
bond migration observed with alkyl-substituted internal alkynes
and double hydrometalation observed with terminal alkynes.
5. Some reactions involve more than one process. For
example, the reaction with (n-Pr)3Al and Cp2ZrCl2 involves
simultaneously hydrometalation and C-H activation.
Although capricious and initially unpredictable, the results
herein presented as well as those reported earlier together with
the mechanistic interpretations discussed above help provide a
reasonable overview of the reactions of alkynes with orga-
noalanes and zirconocene derivatives, which may be used even
in a predictable manner. Perhaps most significantly, a novel
bimetallic mode of â C-H activation and a catalytic principle
involving such a C-H activation have been unravelled. This
study should provide a foundation on which to further develop
additional catalytic reactions.
Reaction of Various Alkynes with Et3Al in the Presence of a
Catalytic Amount of Cp2ZrCl2 in Hexanes or Benzene. (a)
5-Decyne. Representative Procedure. A mixture of Cp2ZrCl2 (0.059
g, 0.2 mmol) and 5-decyne (0.36 mL, 2 mmol) in hexanes (4 mL) cooled
to 0 °C was treated with Et3Al (0.82 mL, 6 mmol) and warmed to 23
°C. After 6 h, analysis of a protonolyzed aliquot by GLC indicated
that the reaction was complete. (i) Protonolysis. The reaction mixture
was cooled to 0 °C and quenched with 3 N HCl and THF (5 mL),
extracted with pentane, washed with NaHCO3 and H2O, dried over
MgSO4, and concentrated. Analysis of the product by NMR spectros-
copy indicated the formation of (Z)-5-ethyl-5-decene in >95% yield
(GLC). After Kugelrohr distillation (oven temperature ) 50 °C at 5
mmHg), 0.284 g (85%) of (Z)-5-ethyl-5-decene19 was obtained: g97%
1
Z; H NMR (CDCl3, Me4Si) δ 0.8-0.95 (m, 6 H), 0.98 (t, J ) 7 Hz,
3 H), 1.2-1.5 (m, 8 H), 1.9-2.15 (m, 6 H), 5.09 (t, J ) 7 Hz, 1 H);
13C NMR (CDCl3, Me4Si) δ 12.97, 14.06 (2 C), 22.54, 22.97, 27.48,
29.67, 29.99, 30.91, 32.56, 123.55, 140.99. (ii) Deuterolysis. In
another run, the reaction mixture was quenched at 0 °C with DCl (20
wt % in D2O, 5 mL) and THF (5 mL) and stirred for 2-3 h at 23 °C.
In this case, (Z)-5-deuterio-6-(2-deuterioethyl)-5-decene was obtained
in 92% yield (GLC): 1H NMR (CDCl3, Me4Si) δ 0.8-1.05 (m, 8 H),
1.2-1.45 (m, 8 H), 1.9-2.1 (m, 6 H); 13C NMR (CDCl3, Me4Si) δ
12.65 (5, J ) 19 Hz), 14.05 (2 C), 22.52, 22.94, 27.35, 29.49, 29.97,
30.88, 32.51, 123.14 (t, J ) 23 Hz), 140.90; g98% D at the Me of the
ethyl group and g98% D at C-5. (iii) Iodinolysis. In the third run (1
mmol scale), the reaction mixture was quenched with a solution of I2
(3.1 g, 12.2 mmol) in THF (13 mL) at 0 °C and stirred at 23 °C for
8-10 h. After workup, purification by column chromatography af-
forded 0.21 g (54%, 69% by NMR) of (E)-5-iodo-6-(2-iodoethyl)-
5-decene: 1H NMR (CDCl3, Me4Si) δ 0.91 (t, J ) 7 Hz, 3 H), 0.92 (t,
J ) 7 Hz, 3 H), 1.25-1.45 (m, 6 H), 1.45-1.6 (m, 2 H), 2.19 (t, J )
7.5 Hz, 2 H), 2.49 (t, J ) 7.5 Hz, 2 H), 2.79 (t, J ) 9.5 Hz, 2 H), 3.15
(t, J ) 9.5 Hz, 2 H); 13C NMR (CDCl3, Me4Si) δ 1.46, 13.89, 14.00,
21.60, 22.58, 30.93, 31.56, 31.83, 41.00, 46.86, 107.78, 143.06.
(b) Diphenylacetylene. The corresponding reaction of dipheny-
lacetylene required heating for 75 h at 55 °C for completion. (i)
Protonolysis. After quenching the mixture as above, examination of
the crude product by NMR spectroscopy indicated the formation of
(Z)-1,2-diphenyl-1-butene30 in 16% NMR yield (using CH2Br2 as an
internal standard) and (E,E)-1,2,3,4-tetraphenyl-1,3-butadiene23b in 69%
NMR yield (based on diphenylacetylene). (ii) Deuterolysis. Deu-
terolysis provided a 2:1 mixture of (Z)-1,4-dideuterio-1,2-diphenyl-1-
butene and (E,E)-1,4-dideuterio-1,2,3,4-tetraphenyl-1,3-butadiene which
yielded the following spectral data. (Z)-1,4-Dideuterio-1,2-diphenyl-
1-butene: g98% D at C-1 and C-4; 1H NMR (CDCl3, Me4Si) δ 1.0-
1.1 (m, 2 H), 2.49 (t, J ) 7 Hz, 2 H), 6.7-7.45 (m, 10 H); 13C NMR
(CDCl3, Me4Si) δ 12.59 (t, J ) 19 Hz), 33.37, 124.67 (t, J ) 23 Hz),
125.98, 126.75, 127.73, 128.45 (2 C), 128.90, 137.41, 141.44, 144.77.
(E,E)-1,4-Dideuterio-1,2,3,4-tetraphenyl-1,3-butadiene: g98% D at
Experimental Section
General. Manipulations involving organometallics were carried out
under an atmosphere of N2 or Ar. Hexanes, 1,2-dichloroethane,
benzene, and toluene were distilled from CaH2; tetrahydrofuran from
sodium benzophenone ketyl; and HMPA from triphenylmethyllithium.
Di(n-propyl)aluminum chloride was prepared in situ by mixing (n-
Pr)3Al and AlCl3 in a 2:1 molar ratio.16 Chloro(methyl)zirconocene
was prepared by conversion of Cp2ZrCl2 to O(ZrCp2Cl)2 followed by
the treatment of the latter with Me3Al.17 The other starting materials
were purchased from commercial sources and used as received. 1H
and 13C NMR spectra were recorded on Varian Gemini-200, Varian
VXR-500, GE QE-300, and JEOL EX-270 FT NMR spectrometers.
Reaction of 5-Decyne with Et3Al in the Presence of a Catalytic
Amount of Cp2ZrCl2 in 1,2-Dichloroethane. The reaction of 5-de-
cyne (0.36 mL, 2 mmol) with Et3Al (0.82 mL, 6 mmol) and Cp2ZrCl2
(59 mg, 0.2 mmol) in (CH2Cl)2 (4 mL) for 72 h at 23 °C gave, after
protonolysis, (Z)-5-ethyl-5-decene in 67% yield along with (Z)-5-decene
(5%), (E,E)-6,7-di(n-butyl)-5,7-dodecadiene19 (2% based on 5-decyne),
and (E,E)-6-(n-butyl)-9-ethyl-7-(n-propyl)-5,7-tridecadiene (13% based
on 5-decyne): 1H NMR (CDCl3, Me4Si) δ 0.7-1.0 (m, 12 H), 0.98 (t,
J ) 7 Hz, 3 H), 1.05-1.5 (m, 16 H), 1.8-2.15 (m, 8 H), 2.75-2.9 (m,
1 H), 4.93 (d, J ) 10 Hz, 1 H), 5.09 (t, J ) 7 Hz, 1 H); 13C NMR
(CDCl3, Me4Si) δ 13.06, 14.06 (3 C), 14.28, 20.79, 22.47, 23.12, 23.21,
27.51, 29.29, 29.59, 30.15, 30.73, 31.87, 32.45, 37.28, 44.26, 124.10,
127.78, 140.45, 142.76. Deuterolysis gave a 1:1 mixture of (Z)-5-
deuterio-6-ethyl-5-decene and (Z)-5-deuterio-6-(2-deuterioethyl)-5-
1
C-1 and C-4; H NMR (CDCl3, Me4Si) δ 6.7-7.45 (m, 20 H); 13C
NMR (CDCl3, Me4Si) δ 126.56, 127.29, 127.73, 128.76, 129.40, 130.29,
131.21 (t, J ) 23 Hz), 137.07, 139.66, 145.39. The use of benzene as
a solvent instead of hexanes led to a considerable acceleration of the
carboalumination reaction, which was complete in 19 h at 55 °C. After
deuterolysis, the two products mentioned above were obtained as a
1:1 mixture in 90% combined yield. Deuterium incorporation was
g98% at all deuterated carbons.
(c) 1-Decyne. This reaction was complete in 17 h at 23 °C in
benzene. (i) Protonolysis. Quenching the mixture with 3 N HCl and
THF provided, after the usual workup, a 90% yield (GLC) of a 1:1
mixture of 2-ethyl-1-decene28 [1H NMR (CDCl3, Me4Si) δ 0.8-0.95
(30) Takahashi, T.; Xi, Z.; Rousset, C. J.; Suzuki, N. Chem. Lett. 1993,
1001.

9586 J. Am. Chem. Soc., Vol. 118, No. 40, 1996
Negishi et al.
(m, 3 H), 1.02 (t, J ) 7 Hz, 3 H), 1.2-1.5 (m, 12 H), 1.95-2.1 (m, 4
H), 4.68 (s, 2 H); 13C NMR (CDCl3, Me4Si) δ 12.37, 14.10, 22.77,
27.96, 28.77, 29.43, 29.57, 29.66, 32.02, 36.36, 107.33, 151.65] and
(E)-3-dodecene29 [1H NMR (CDCl3, Me4Si) δ 0.8-0.95 (m, 3 H), 0.96
(t, J ) 7 Hz, 3 H), 1.2-1.4 (m, 12 H), 1.9-2.1 (m, 4 H), 5.3-5.5 (m,
2 H); 13C NMR (CDCl3, Me4Si) δ 13.99, 14.08, 22.77, 25.67, 29.31,
29.43, 29.62, 29.77, 32.02, 32.67, 129.37, 131.83]. (ii) Deuterolysis.
Quenching the reaction mixture with DCl (20 wt % in D2O, 5 mL)
EtZrCp2Cl-Et3-nAlCln at various times along with those of 10 indicated
in parentheses are as follows: 91% (<5%) at 5 min, 81% (<5%) at 1
h, 75% (<5%) at 2 h, 55% (20%) at 3 h, 37% (26%) at 4 h, and <5%
(17%) at 14 h. The signals for EtZrCp2Cl-Et3-nAlCln are as follows:
1H NMR for Cp δ 5.75; 13C NMR for Cp δ 112.95; 13C NMR for
CH2-Zr δ 53.76.
NMR Examination of the Reaction of Cp2ZrCl2 with 1 Equiv of
Et3Al. To the suspension of Cp2ZrCl2 (292 mg, 1 mmol) in 5 mL of
C6D6 was added Et3Al (0.143 mL, 1 mmol). Examination of the
reaction mixture by NMR spectroscopy revealed that the reaction was
complete in 20 min and that EtZrCp2Cl-Et2AlCl was formed in about
75% yield: 1H NMR (Cp) δ 5.80; 13C NMR (Cp) δ 112.45; 13C NMR
(CH2-Zr) δ 49.20. No detectable changes were seen over 24 h at
ambient temperatures. After quenching with THF (0.05 mL) NMR
spectroscopy indicated that 25% of Cp2ZrCl2 remained unreacted, with
the rest having been converted to EtZrCp2Cl (72%); 1H NMR (CDCl3,
Me4Si) δ 1.05 (q, J ) 7.3 Hz, 2 H), 1.35 (t, J ) 7.3 Hz, 3 H), 5.70 (s,
10 H); 13C NMR (CDCl3, Me4Si) δ 18.52, 46.67, 112.52.
Preparation of EtZrCp2Cl. In a dry round-bottomed flask equipped
with a stirring bar, a septum inlet, and a mercury bubbler under argon
were placed HZrCp2Cl (1.0 g, 3.88 mmol) and 16 mL of C6D6. Argon
was replaced with ethylene and the suspension was rapidly stirred until
all solid material dissolved (3 h). NMR examination of the reaction
mixture indicated that EtZrCp2Cl (0.27 M in C6D6) was formed in 90%
yield. 1H NMR (C6D6, Me4Si) δ 1.12 (q, J ) 7.5 Hz, 2 H), 1.43 (5,
J ) 7.5 Hz, 3 H), 5.82 (s, 10 H); 13C NMR (C6D6, Me4Si) δ 18.38,
46.53, 112.34.
Reaction of EtZrCp2Cl with EtAlCl2. In a dry NMR tube under
argon was placed a solution of EtZrCp2Cl in C6D6 (1.0 mL, 0.27 M,
0.27 mmol). To this solution at 5 °C was added EtAlCl2 (0.034 mL,
0.27 mmol). Immediate precipitation of Cl2ZrCp2 was observed. After
treatment with THF (0.05 mL) NMR analysis indicated that <0.5% of
EtZrCp2Cl remained unreacted, with the rest being converted to Cl2-
ZrCp2.
and THF (5 mL) provided
a 1:1 mixture of (E)-1-deuterio-
2-(2-deuterioethyl)-1-decene and (E)-1,4-dideuterio-3-dodecene.
(E)-1-Deuterio-2-(2-deuterioethyl)-1-decene: 96% D at C-1; 46% D
at the Me of the ethyl group; 13C NMR (CDCl3, Me4Si) δ 12.07 (t, J
) 20 Hz), 14.11, 22.81, 28.00, 28.67 (signal of the fraction deuterated
at the Me of the ethyl group), 28.75 (signal of the fraction protonated
at the Me of the ethyl group), 29.48, 29.61, 29.70, 32.06, 36.37, 107.10
(t, J ) 23.5 Hz), 151.50. (E)-1,4-Dideuterio-3-dodecene: >90% D
at C-4; 92% D at C-1; 13C NMR (CDCl3, Me4Si) δ 13.72 (t, J ) 19
Hz), 14.11, 22.81, 25.57, 29.36, 29.48, 29.67, 29.80, 32.06, 32.60,
129.05 (t, J ) 23 Hz), 131.75.
(d) Phenylacetylene. This reaction was complete after 7 h at 55
°C in hexanes. (i) Protonolysis. After protonolysis with 3 N HCl,
examination of the product by NMR spectroscopy indicated the
formation of (E)-1-phenyl-1-butene30 [1H NMR (CDCl3, Me4Si) δ 1.08
(t, J ) 7 Hz, 3 H), 2.22 (qd, J ) 7 and 7 Hz, 2 H), 6.25 (dt, J ) 16
and 6 Hz, 1 H), 6.37 (d, J ) 16 Hz, 1 H), 7.1-7.5 (m, 5 H); 13C NMR
(CDCl3, Me4Si) δ 13.63, 26.05, 125.88, 126.71, 128.43, 128.78, 132.57,
137.91] and 2-phenyl-1-butene30 [1H NMR (CDCl3, Me4Si) 1.10 (t, J
) 7 Hz, 3 H), 2.50 (q, J ) 7 Hz, 2 H), 5.05 (s, 1 H), 5.27 (s, 1 H),
7.1-7.5 (m, 5 H); 13C NMR (CDCl3, Me4Si) δ 12.92, 28.04, 110.90,
125.98, 127.22, 128.19, 141.51, 150.01] in a 2:1 ratio in 84% combined
NMR yield (using CH2Br2 as an internal standard). (ii) Deuterolysis.
In another run, the reaction mixture was quenched with DCl/D2O at
-78 °C. Examination of the product by NMR spectroscopy indicated
the formation of a 2:1 mixture of (E)-1,4-dideuterio-1-phenyl-1-butene
1
and 1,4-dideuterio-2-phenyl-1-butene. Analysis of their H and 13C
Reaction of EtZrCp2Cl with Et2AlCl. In a dry NMR tube under
argon was placed a solution of EtZrCp2Cl in C6D6 (1.0 mL, 0.27 M,
0.27 mmol). To this solution at 5 °C was added Et2AlCl (0.034 mL,
0.27 mmol). NMR examination of the reaction mixture revealed that
the reaction was complete in 5 min. After treatment with THF (0.05
mL) NMR analysis indicated that 80% of EtZrCp2Cl remained
unreacted, with the rest being converted to Cl2ZrCp2 (16%).
Reaction of EtZrCp2Cl with Et3Al. In a dry NMR tube under
argon was placed a solution of EtZrCp2Cl in C6D6 (1.0 mL, 0.27 M,
0.27 mmol). To this solution at 5 °C was added Et3Al (0.037 mL,
0.27 mmol), and the reaction mixture was kept at 23 °C for 0.5 h.
NMR examination of the reaction mixture indicated that 10 was formed
in 83% yield: 1H NMR (C6D6, Me4Si) δ 0.23-0.3 (m, 4 H), 0.26-
0.35 (m, 2 H), 1.37 (t, J ) 7.9 Hz, 6 H), 1.4-1.48 (m, 2 H), 5.43 (s,
10 H); 13C NMR (C6D6, Me4Si) δ -0.63, 4.55 (br, 2 C), 9.31 (2 C),
36.94, 108.25 (10 C).
Reaction of 10 with 5-Decyne. Solution of 10 (0.225 mmol) in
C6D6 prepared as described above was treated with 5-decyne (31 mg,
0.225 mmol) in an NMR tube, and the reaction mixture was kept at 23
°C for 10 min. NMR examination of the reaction mixture indicated
that EtZrCp2Cl was formed in 90% yield based on the integration of
the 1H NMR Cp signal at 5.83 ppm. After deuterolysis with 4% DCl,
the reaction mixture was extracted with Et2O, washed with water, dried
over MgSO4, filtered, and concentrated. Analysis by GLC and NMR
spectroscopy indicated the formation of (Z)-5-(ethyl-2′-d1)-5-decene-
6-d1 in 95% yield (>95% D at C-6; >98% D at C-2′).
NMR Examination of the Reaction of 2,3-Di(n-butyl)-1,1-bis-
(cyclopentadienyl)-1-zircona-2-cyclopentene with Et2AlCl. In a dry
round-bottomed flask equipped with a stirring bar, a septum inlet, and
a mercury bubbler were placed Cp2ZrCl2 (292 mg, 1 mmol) and 5 mL
of C6D6 under an atmosphere of ethylene. To this suspension was added
dropwise at 5 °C n-BuLi (2 M in cyclohexane, 1 mL, 2 mmol). After
stirring for 1 h at 23 °C under an atmosphere of ethylene, 5-decyne
(0.18 mL, 1 mmol) was added, and ethylene was replaced with argon.
NMR examination after 1 h indicated the formation of 6 in 90% yield,
as judged from the NMR signals of Cp: 1H NMR δ 5.9 (s); 13C NMR
δ 110.63. Treatment of the reaction mixture with Et2AlCl (0.13 mL,
1 mmol) afforded EtZrCp2Cl in 65% yield, as judged from the NMR
NMR spectra indicated that the extents of D incorporation at C-1 were
91 and 92% and those at C-4 were 42% for the 1-phenyl isomer and
95% for the 2-phenyl isomer.
Reaction of 5-Decyne with Et3Al in the Presence of 1 Equiv of
Cp2ZrCl2. (a) (Z)-5-(Ethyl-2′-d1)-5-decene-6-d1 (1). Representative
Procedure. In a dry round-bottomed flask equipped with a stirring
bar, a septum inlet, and a mercury bubbler were placed Cp2ZrCl2 (877
mg, 3 mmol) and 15 mL of benzene. To this suspension were added
Et3Al (1.25 mL, 9 mmol) and 5-decyne (0.54 mL, 3 mmol), and the
reaction mixture was stirred at 23 °C for 2 h. NMR examination of
the reaction mixture after quenching with THF (0.2 mL) indicated the
formation of Cp2Zr(Et)Cl in 60% yield, as judged from NMR signals
of Cp (1H NMR δ 5.80 (s); 13C NMR δ 112.53) and CH2-Zr (13C
NMR δ 47.12). After deuterolysis with 4% DCl, the reaction mixture
was extracted with Et2O, washed with water, dried over MgSO4, filtered,
and concentrated. Analysis of the product by GLC and NMR
spectroscopy indicated the formation of the title compound in 84%
yield (>95% D at C-6; 90% D at C-2′).
(b) (Z)-5-Ethyl-5-decene-6-d1 (7). This reaction was performed as
described above using 0.42 mL (3 mmol) of Et3Al. It was complete
in 7 h. Analysis of the deuterolysis product by GLC and NMR
spectroscopy indicated the formation of 7 in 65% yield (g80% D at
C-6; 18% D at C-2′).
(c) (Z)-5-(Ethyl-2′-d2)-5-decene-6-d1 (8). To the suspension of Cp2-
ZrCl2 (988 mg, 3 mmol) in 15 mL of benzene was added Et3Al (1.25
mL, 9 mmol), and the reaction mixture was stirred at 23 °C for 24 h.
To the resultant mixture was added 5-decyne (0.43 mL, 2.4 mmol).
the reaction mixture was stirred for 15 min, quenched with 4% DCl,
extracted with Et2O, washed with water, dried over MgSO4, filtered,
and concentrated. Analysis of the product by GLC and NMR
spectroscopy indicated the formation of 8 in 87% yield (>95% D at
C-6; 83% CHD2 and 17% CH2D at C-2′).
NMR Examination of the Reaction of 5-Decyne with Et3Al in
the Presence of 1 Equiv of Cp2ZrCl2. The reaction of 5-decyne with
3 equiv of Et3Al in the presence of 1 equiv of Cp2ZrCl2 was carried
out as described above on 1 mmol scale. An aliquot was withdrawn
and periodically examined by NMR spectroscopy. The amounts of

Zirconium-Catalyzed Carboalumination of Alkynes
J. Am. Chem. Soc., Vol. 118, No. 40, 1996 9587
signals of Cp (1H NMR δ 5.75 (s); 13C NMR δ 112.47) and CH2-Zr
(13C NMR δ 46.58).
5-decene: 1H NMR (CDCl3, Me4Si) δ 0.8-0.95 (m, 6 H), 0.97 (t, J )
7 Hz, 3 H), 1.2-1.55 (m, 8 H), 2.17 (t, J ) 7.5 Hz, 2 H), 2.23 (q, J
) 7 Hz, 2 H), 2.49 (t, J ) 7.5 Hz, 2 H); 13C NMR (CDCl3, Me4Si) δ
12.07, 13.91, 14.03, 21.64, 22.71, 30.78, 30.92, 32.02, 35.72, 40.88,
104.14, 145.00.
Reaction of 5-Decyne with Et3Al in the Presence of a Catalytic
Amount of Cp2Zr(n-Bu)2. In a dry round-bottomed flask equipped
with a stirring bar, a septum inlet, and a mercury bubbler were placed
Cp2ZrCl2 (58 mg, 0.2 mmol) and 5 mL of toluene. This suspension at
-78 °C was treated with n-BuLi (2.5 M in hexanes, 0.16 mL, 0.4
mmol). The resultant clear yellow solution was slowly warmed to 0
°C and treated with Et3Al (0.14 mL, 1 mmol) and 5-decyne (0.18 mL,
1 mmol). After 24 h at 23 °C the reaction mixture was quenched with
4% HCl, extracted with Et2O, wshed with water, dried over MgSO4,
filtered, and concentrated. Analysis by GLC indicated the formation
of (Z)-5-ethyl-5-decene in <5% yield.
Reaction of 5-Decyne with Et3Al in the Presence of Catalytic
Amounts of Cp2Zr(n-Bu)2 and Et2AlCl. In a dry round-bottomed
flask equipped with a stirring bar, a septum inlet, and a mercury bubbler
were placed Cp2ZrCl2 (58 mg, 0.2 mmol) and 5 mL of toluene. This
suspension at -78 °C was treated with n-BuLi (2.5 M in hexanes, 0.16
mL, 0.4 mmol). The resultant clear yellow solution was slowly warmed
to 0 °C and treated with Et3Al (0.14 mL, 1 mmol), 5-decyne (0.18
mL, 1 mmol), and Et2AlCl (0.025 mL, 0.2 mmol). After 1 h at 23 °C
the reaction mixture was quenched with 4% DCl, extracted with Et2O,
washed with water, dried over MgSO4, filtered, and concentrated.
Analysis by GLC and NMR spectroscopy indicated the formation of
(Z)-5-(2′-dideuterioethyl)-6-deuterio-5-decene in 73% yield (>90% D
at C-6; >98% D at C-2′).
Reaction of 5-Decyne with Et3Al in the Presence of Catalytic
Amounts of Zirconocene Derivatives. (a) Use of 0.2 equiv of 6. No
reaction of 5-decyne with Et3Al (1.2 equiv) was observed in the
presence of 6 (0.2 equiv) prepared by the reaction of Et2ZrCp2 and
5-decyne. However, addition of Et2AlCl (0.2 equiv) to the mixture
did induce the expected reaction to give, after deuterolysis, a 40% yield
of 1.
(b) Use of 0.1 equiv of a Mixture of 6 and Et2AlCl. The reaction
of 5-decyne with Et3Al (1.2 equiv) was carried out in hexanes in the
presence of 0.1 equiv each of 6 and Et2AlCl. After deuterolysis, 1
was produced in 85% yield.
(b) Reaction of 5-Decyne Using a Catalytic Amount of Cp2ZrCl2.
This reaction was carried out similarly using 0.059 g (0.2 mmol) of
Cp2ZrCl2. After 20 h at 55 °C, GLC analysis of a protonolyzed aliquot
indicated the formation of (Z)-5-ethyl-5-decene in >90% yield along
with 8-10% of (E,E)-6,7-di(n-butyl)-5-ethyl-5,7-dodecadiene (based
on 5-decyne). (i) Protonolysis. The reaction mixture was cooled to
0 °C and quenched with THF (5 mL) and 3 N HCl. After the usual
workup, Kugelrohr distillation (oven temperature ) 50 °C at 5 mmHg)
provided two products. After filtration (silica gel-pentane), (Z)-5-
ethyl-5-decene was obtained in 70% yield (0.235 g). Also obtained
was (E,E)-6,7-di(n-butyl)-5-ethyl-5,7-dodecadiene isolated in 4% yield
(0.022 g): 1H NMR (CDCl3, Me4Si) δ 0.8-1.0 (m, 15 H), 1.15-2.05
(m, 18 H), 1.9-2.1 (m, 8 H), 4.97 (t, J ) 7 Hz, 1 H); 13C NMR (CDCl3,
Me4Si) δ 14.05 (3 C), 14.12 (2 C), 22.43, 22.73, 23.08, 23.16, 25.68,
27.43, 29.43, 29.54, 29.87, 30.36, 30.98, 31.27, 32.31, 127.32, 135.70,
137.67, 139.93. (ii) Deuterolysis. In another run, the reaction mixture
was quenched with THF (5 mL) and DCl (20 wt % in D2O, 5 mL) at
0 °C. After stirring for 5 h at 23 °C, the usual extractive workup
(pentane) afforded (Z)-5-deuterio-6-ethyl-5-decene and (E,E)-6,7-di-
(n-butyl)-5-deuterio-8-ethyl-5,7-dodecadiene. After separation by Kugel-
rohr distillation and filtration through silica gel (pentane) (Z)-5-deuterio-
6-ethyl-5-decene was obtained in 72% isolated yield (0.242 g) (g95%
D by 13C NMR). (E,E)-6,7-Di(n-butyl)-5-deuterio-8-ethyl-5,7-dodeca-
diene was also obtained in 6% yield (0.039 g): 1H NMR (CDCl3, Me4-
Si) δ 0.8-1.0 (m, 15 H), 1.1-1.45 (m, 18 H), 1.9-2.1 (m, 8 H); 13C
NMR (CDCl3, Me4Si) δ 14.06 (3 C), 14.13 (2 C), 22.44, 22.74, 23.09,
23.18, 25.69, 27.33, 29.39, 29.55, 29.86, 30.37, 30.98, 31.28, 32.30,
126.95 (t, J ) 23 Hz), 135.69, 137.64, 139.81; g94% D by 13C NMR.
(c) Reaction of Diphenylacetylene Using a Catalytic Amount of
Cp2ZrCl2. This reaction was complete after 36-40 h at 70-75 °C
and gave, after hydrolysis, (Z)-1,2-diphenyl-1-butene30 in 60% NMR
yield (using CH2Br2 as an internal standard): 1H NMR (CDCl3, Me4-
Si) δ 1.06 (t, J ) 7 Hz, 3 H), 2.50 (q, J ) 7 Hz, 2 H), 6.42 (s, 1 H),
6.7-7.45 (m, 10 H); 13C NMR (CDCl3, Me4Si) δ 12.88, 33.47, 125.00,
125.94, 126.72, 127.70, 128.38, 128.43, 128.89, 137.43, 141.37, 144.81.
(d) Reaction of 1-Decyne Using a Catalytic Amount of Cp2ZrCl2.
This reaction was complete after 5 h at 23 °C. (i) Protonolysis.
Protonolysis afforded a 3:1 mixture of 2-ethyl-1-decene and (E)-3-
dodecene in 91% yield (GLC). (ii) Deuterolysis. Quenching the
reaction mixture with THF and DCl (20 wt % in D2O, 5 mL) provided
after workup a 3:1 mixture of (E)-1-deuterio-2-ethyl-1-decene and (E)-
4-deuterio-3-dodecene. (E)-1-Deuterio-2-ethyl-1-decene: g87% D
by 13C NMR; 13C NMR (CDCl3, Me4Si) δ 12.35, 14.10, 22.80, 27.99,
28.74, 29.46, 29.60, 29.69, 32.05, 36.35, 107.08 (t, J ) 23 Hz), 151.53.
(E)-4-Deuterio-3-dodecene: g87% D by 13C NMR; 13C NMR (CDCl3,
Me4Si) δ 14.00, 14.10, 22.80, 25.65, 29.34, 29.52, 29.66, 29.78, 32.05,
32.59, 129.06 (t, J ) 23 Hz), 131.75.
Reaction of 5-Decyne with Et2AlCl in Hexanes in the Presence
of Cp2ZrCl2. Addition of Et2AlCl (1 equiv) to a mixture of 5-decyne
in the presence of either 0.1 or 1 equiv of Cp2ZrCl2 in hexanes did not
induce any reaction over at least 1 day at 23 °C, with g90-95% of
the starting materials remaining unreacted.
Reaction of Various Alkynes with Et2AlCl in (CH2Cl)2 in the
Presence of the Stoichiometric or a Catalytic Amount of Cp2ZrCl2.
(a) Reaction of 5-Decyne Using the Stoichiometric Amount of
Cp2ZrCl2. A solution of Cp2ZrCl2 (0.586 g, 2 mmol) and 5-decyne
(0.36 mL, 2 mmol) in (CH2Cl)2 (4 mL) was treated at 0 °C with Et2-
AlCl (0.75 mL, 6 mmol), and the mixture was warmed to 23 °C. After
20 h, analysis by GLC of a protonolyzed aliquot using nonane as an
internal standard indicated that the reaction was essentially complete
and that (Z)-5-ethyl-5-decene was formed in 90% yield along with
4-5% of (E,E)-6,7-di(n-butyl)-5-ethyl-5,7-dodecadiene (based on 5-de-
cyne). An aliquot (0.6 mL) was transferred into a 5-mm NMR tube
containing C6D6 (0.2 mL). THF (0.6 mL) was added to dissolve all
NMR Examination of Et2AlCl and Cp2ZrCl2. A solution of Cp2-
ZrCl2 (0.146 g, 0.5 mmol) and Et2AlCl (0.065 mL, 0.52 mmol) in CD2-
1
Cl2 (1.5 mL) was examined by H and 13C NMR spectroscopies over
1
insoluble materials. Examination of this mixture by H NMR using
a period of 24 h. Examination after 10 min, 4 h, and 24 h using
mesitylene as an internal standard indicated that Cp2ZrCl2 and Et2AlCl
were remaining unreacted to the extents of >95%. The extent of the
formation of EtZrCp2Cl was below the detection limit of 0.1%.
Reaction of 5-Decyne with Et3Al in the Presence of the Stoichio-
metric Amount of MeZrCp2Cl. (a) In Hexanes. A solution of
MeZrCp2Cl17 (0.157 g, 0.58 mmol) and 5-decyne (104 µL, 0.58 mmol)
in hexanes (2 mL) was treated at 0 °C with Et3Al (0.08 mL, 0.59 mmol)
and stirred for 2 h at 23 °C. After deuterolysis, analysis of the product
by GLC and NMR spectroscopy indicated the formation of (Z)-5-
deuterio-6-(2-deuterioethyl)-5-decene (1) in 67% yield (g90% D at
C-5 and g92% D at Me of the ethyl group), along with a 20% yield
(based on 5-decyne) of (E,E)-6,7-di(n-butyl)-5,8-dideuterio-5,7-dodeca-
diene (g90% D at C-5 and C-8).
mesitylene as an internal standard indicated that Cp2ZrCl2 was recovered
to the extent of g95% yield. (i) Deuterolysis. The reaction mixture
was cooled to 0 °C and quenched with THF (2 mL) and D2O (2 mL).
After stirring for 12 h at 23 °C, the reaction mixture was extracted
with pentane, washed with NaHCO3 and H2O, dried over MgSO4,
filtered, and concentrated. Filtration through silica gel (pentane) fol-
lowed by concentration provided 0.24 g (71%) of (Z)-5-deuterio-
6-ethyl-5-decene: 1H NMR (CDCl3,Me4Si) δ 0.8-0.95 (m, 6 H), 0.98
(t, J ) 7 Hz, 3 H), 1.2-1.45 (m, 8 H), 1.9-2.15 (m, 6 H); 13C NMR
(CDCl3, Me4Si) δ 12.94, 14.05 (2 C), 22.53, 22.96, 27.37, 29.59, 29.97,
30.90, 32.52, 123.17 (t, J ) 23 Hz), 140.89; g95% D incorporation
by 13C NMR. (ii) Iodinolysis. In another run, the mixture was treated
with a solution of I2 (3.05 g, 12 mmol) in THF (10 mL) at 0 °C and
warmed to 23 °C for 12 h. The mixture was then quenched with 3 N
HCl, extracted with Et2O, washed with Na2S2O3, NaHCO3, and H2O,
and dried over MgSO4. Filtration through silica gel (pentane) followed
by concentration provided 0.49 g (84%) of (E)-6-ethyl-5-iodo-
(b) In 1,2-Dichloroethane. The corresponding reaction run in 1,2-
dichloroethane required 12-24 h at 23 °C for completion and produced,
after deuterolysis, 1 in 69% yield (81% D at C-5; 85% D at Me of the

9588 J. Am. Chem. Soc., Vol. 118, No. 40, 1996
Negishi et al.
ethyl group). The formation of two dimeric products (e9% combined
yield based on 5-decyne) was detected by GLC.
of (Z)-5-decene (0.42 mmol), (Z)-4-decene (0.24 mmol), and (5E,7E)-
6,7-di(n-butyl)-5,7-dodecadiene (0.15 mmol).
Reaction of 5-Decyne with Et2AlCl in the Presence of the
Stoichiometric Amount of MeZrCp2Cl. The reaction of 5-decyne
with 3 equiv of Et2AlCl and 1 equiv of MeZrCp2Cl in (CH2Cl)2 was
carried out similarly. After deuterolysis, (Z)-5-ethyl-6-deuterio-5-
decene (7) was produced in 93% yield (g91% D at C-6). The extent
of formation of (Z)-5-methyl-5-decene was <2%.
(b) Use of a Catalytic Amount of MeZrCp2Cl in 1,2-Dichloro-
ethane. The corresponding reaction (1 mmol scale) run in (CH2Cl)2
was complete after 48 h at 23 °C and gave, after hydrolysis, (Z)-5-
decene (0.63 mmol), (Z)-4-decene (0.12 mmol), (Z)-5-(n-propyl)-5-
decene (0.11 mmol), and (5E,7E)-di(n-butyl)-5,7-dodecadiene (0.033
mmol).
(c) Use of the Stoichiometric Amount of MeZrCp2Cl in Hexanes.
The corresponding reaction in hexanes using 1 equiv of MeZrCp2Cl
gave, after 1 h at 23 °C and hydrolysis, (Z)-5-decene (0.31 mmol),
(Z)-4-decene (0.27 mmol), and (5E,7E)-6,7-di(n-butyl)-5,7-dodecadiene
(0.20 mmol).
Reaction of Various Alkynes with (n-Pr)3Al in the Presence of a
Catalytic Amount of Cp2ZrCl2. (a) 5-Decyne. Representative
Procedure. To a solution of Cp2ZrCl2 (0.029 g, 0.1 mmol) and 5-decyne
(0.14 g, 1 mmol) in hexanes (2 mL) was added (n-Pr)3Al (0.47 g, 3
mmol), at 0 °C, and the resulting mixture was stirred at 23 °C for 12
h. (i) Protonolysis. The mixture was quenched with 3 N HCl. After
the usual extractive workup, examination by GLC and 13C NMR
spectroscopy indicated the formation of (Z)-5-decene (0.33 mmol), (Z)-
4-decene (0.30 mmol), and (5E,7E)-6,7-di(n-butyl)-5,7-dodecadiene
(0.19 mmol). The identity of these products was established by GLC
coinjection of their authenic samples. (ii) Deuterolysis. Quenching
the reaction mixture with DCl/D2O led to the formation of (Z)-5-
deuterio-5-decene (93% D), (Z)-5-deuterio-4-decene (93% D), and
(5E,7E)-6,7-di(n-butyl)-5,8-dideuterio-5,7-dodecadiene (97% D). (Z)-
5-Deuterio-5-decene: 13C NMR (CDCl3, Me4Si) δ 14.12, 22.48, 27.00,
(d) Use of the Stoichiometric Amount of MeZrCp2Cl in 1,2-
Dichloroethane. The corresponding reaction in (CH2Cl)2 using 1 equiv
of MeZrCp2Cl at 23 °C for 1 h produced, after hydrolysis, (Z)-5-decene
(0.24 mmol), (Z)-4-decene (0.21 mmol), (Z)-5-(n-propyl)-5-decene (0.08
mmol), and (5E,7E)-6,7-di(n-butyl)-5,7-dodecadiene (0.15 mmol).
Reaction of 5-Decyne with (n-Pr)2AlCl in the Presence of a
Catalytic Amount of Cp2ZrCl2. (a) In (CH2Cl)2. A solution of Cp2-
ZrCl2 (0.029 g, 0.1 mmol) and 5-decyne (0.14 g, 1 mmol) in (CH2Cl)2
(1 mL) was treated at 0 °C with (n-Pr)2AlCl (3 mmol), generated by
mixing (n-Pr)3Al (0.31 g, 2 mmol) with dry AlCl3 (0.13 g, 1 mmol) in
(CH2Cl)2 (1 mL). The reaction mixture was heated at 50 °C for 12 h.
(i) Protonolysis. In one run the reaction mixture was quenched with
3 N HCl, extracted with pentane, washed with NaHCO3, and dried over
MgSO4. Examination of the product by GLC and NMR spectroscopy
indicated the formation of a 75% yield of (Z)-5-(n-propyl)-5-decene:
13C NMR (CDCl3, Me4Si) δ 13.93, 14.11, 21.41, 22.51, 22.98, 27.48,
29.79, 30.88, 32.52, 39.22, 124.94, 139.28. (ii) Deuterolysis. Deu-
terolysis of the reaction mixture with DCl (20 wt % in D2O) led to the
1
32.12, 129.53 (| JCD| ) 23 Hz), 129.76. (Z)-5-Deuterio-4-decene: 13C
NMR (CDCl3, Me4Si) δ 13.85, 14.12, 22.73, 23.03, 27.21, 29.39, 29.59,
1
31.68, 129.53, 129.76 (| JCD| ) 23 Hz). (5E,7E)-6,7-Di(n-butyl)-5,8-
dideuterio-5,7-dodecadiene: 13C NMR (CDCl3, Me4Si) δ 14.05, 22.61,
1
22.90, 27.79, 27.93, 31.30, 32.43, 125.63 (| JCD| ) 23 Hz), 141.21.
(b) 3-Hexyne. This reaction was run similarly at 50 °C for 3 h.
After deuterolysis, a roughly 1:1 mixture of (Z)-3-deuterio-3-hexene
and (Z)-3-deuterio-2-hexene was obtained. The extents of D incorpora-
tion were >90%. More critically, no D incorporation was observed at
C-2 of (Z)-3-deuterio-2-hexene. An authentic sample of (Z)-2-hexene
obtained from a commerical source exhibited 13C NMR signals at
123.86 and 130.69 ppm for the alkenyl carbons.
formation of (Z)-5-(n-propyl)-6-deuterio-5-decene: 88% D at C-6; 13
C
NMR (CDCl3, Me4Si) δ 13.92, 14.10, 21.36. 22.48, 22.94, 27.34,
1
29.74, 30.83, 32.46, 39.11, 124.51 (| JCD| ) 23 Hz), 139.17. Minor
quantities of other products were also detected.
(c) Diphenylacetylene. The corresponding reaction of dipheny-
lacetylene was carried out in toluene at 100 °C for 6 h. After
protonolysis of the reaction mixture, examination of the product by
GLC and NMR spectroscopy indicated the formation of (Z)-stilbene
(0.27 mmol), (E)-stilbene (0.41 mmol), and (1E,3E)-1,2,3,4-tetraphenyl-
1,3-butadiene23b (0.12 mmol).
(b) In Hexanes. The same reaction run in hexanes was examined
after 12 h at 23 °C by GLC and NMR spectroscopy. 5-Decyne was
remaining unreacted to the extent of 75%. (Z)-5-Decene and (Z)-4-
decene were formed in 13 and 10% yield, respectively.
1H NMR Examination of (n-Pr)2AlCl and Cp2ZrCl2. To a
solution of Cp2ZrCl2 (0.29 g, 1 mmol) in (CH2Cl)2 (5 mL) was added
(n-Pr)2AlCl (3 M in (CH2Cl)2, 0.33 mL, 1 mmol). After heating to 80
°C for 6 h, 99% of Cp2ZrCl2 (δ 6.37 ppm) remained unreacted without
a sign for the formation of any other ZrCp2 derivative.
(d) 1-Decyne. The corresponding reaction of 1-decyne in hexanes
was complete in 6 h at 23 °C, and it gave, after hydrolysis, 1-decene
(61%) and n-decane (15%). Deuterolysis led to the formation of (E)-
1-deuterio-1-decene: 98% D at C-1; 13C NMR (CDCl3, Me4Si) δ 14.15,
Reaction of Alkynes with (i-Bu)3Al and a Catalytic Amount of
Cp2ZrCl2. (a) 5-Decyne. To Cp2ZrCl2 (0.029 g, 0.1 mmol) and
5-decyne (3 mmol) in hexanes (2 mL) was added (i-Bu)3Al (0.59 g, 3
mmol) at 0 °C. After stirring for 12 h at 23 °C, deuterolysis provided
a 1:1 mixture of (Z)-5-deuterio-5-decene and (Z)-5-deuterio-4-decene
in 87% combined yield.
(b) 1-Decyne. This reaction was run for 1 h at 23 °C. After
deuterolysis, a 1:1 mixture of (E)-1-deuterio-1-decene and 1,1-
dideuteriodecane was obtained in essentially quantitative yield.
1
22.78, 29.06, 29.27, 29.41, 29.59,32.00, 33.88, 113.85 (| JCD| ) 24
Hz), 139.11.
(e) Phenylacetylene. This reaction gave, after hydrolysis, stryene
in 53% yield.
Reaction of 5-Decyne with (n-Pr)3Al in 1,2-Dichloroethane. The
reaction of 5-decyne (1 mmol) with Et3Al (3 mmol) and a catalytic
amount of Cp2ZrCl2 (0.1 mmol) in (CH2Cl)2 run at 50 °C for 3 h gave,
after hydrolysis, (Z)-5-decene (0.52 mmol), (Z)-4-decene (0.35 mmol),
and (Z)-5-(n-propyl)-5-decene (0.09 mmol).
Acknowledgment. We thank the National Science Founda-
tion (CHE-9402288) for support of this research. Dr. N. Suzuki
kindly provided some experimental results incorporated in this
study.
Reaction of 5-Decyne with (n-Pr)3Al in the Presence of a Catalytic
or the Stoichiometric Amount of MeZrCp2Cl. (a) Use of a Catalytic
Amount of MeZrCp2Cl in Hexanes. A solution of MeZrCp2Cl17
(0.028 g, 0.1 mmol) and 5-decyne (0.14 g, 1 mmol) in hexanes (2 mL)
was treated at 0 °C with (n-Pr)3Al (0.47 g, 3 mmol), and the reaction
mixture was stirred at 23 °C for 24 h. Protonolysis led to the formation
JA9538039