C O M M U N I C A T I O N S
Table 2. Coupling of Aryl Halides with Lithium Amide, Catalyzed
by CyPF-t-BuPdCl2
the primary and secondary arylamine in a combined yield over 90%
a
(eq 1). Further studies are clearly needed to understand the factors
that control selectivity for formation of the primary amine in this
reaction and in the catalytic cycle, but this reaction comprises the
first C-N bond-forming reductive elimination of a parent amido
complex and one of the few reactions of terminal amido complexes
that parallels the typical reactivity of organometallic species. Further
studies of reaction scope and the mechanism of the coupling process
will be the subject of future work.
Acknowledgment. We thank the NIH (GM-55382) for support
2
of this work, Johnson-Matthey for a gift of PdCl , and Solvias for
a gift of the Josiphos ligands.
Supporting Information Available: All experimental procedures
and spectroscopic data of new compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
References
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a
Reactions conducted with 1.0 mol % of Pd(CyPFt-Bu)Cl2, 1 mmol
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c
ArBr, and 10 equiv LiNH2 in 20 mL DME. Isolated yield. Determined
(
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1
d
by H NMR of the crude product. No product, only the phenol was
e
detected. Reaction with 1.99 g of 1-bromo-2-iso-propylbenzene (10 mmol).
primary amine in 81% yield with >50:1 selectivity for the mono-
arylation product. The same reaction conducted on a 2.0 g scale
formed the primary amine in a comparable 82% yield. In addition,
(
4) (a) Weissermel, K.; Arpe, H. J. Industrial Organic Chemistry; Wiley-
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2
2
,2′-dibromobiphenyl reacted with LiNH to give carbazole in an
(
5) Lang, F.; Zewge, D.; Houpis, I. N.; Volante, R. P. Tetrahedron Lett. 2001,
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average yield of 80% for each of two C-N bond-forming processes.
To identify the palladium species that forms the C-N bond, we
conducted stoichiometric reactions of Pd(CyPF-t-Bu)(4-MeOPh)-
(
6) (a) Jaime-Figueroa, S.; Liu, Y.; Muchowski, J. M.; Putman, D. G.
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16
(
Br) 1 with ammonia and base and developed an independent
synthesis of the potential arylpalladium amide intermediate. The
reaction of complex 1 with 5.0 equiv of ammonia and 1.1 equiv of
NaOt-Bu at 90 °C (eq 1) for 1 h formed the coupled product in
0% yield with a 3:1 ratio of monoarylation to diarylation product
by 1H NMR spectroscopy. This reaction occurred through an
intermediate that we detected by P NMR spectroscopy and that
we suspected to be the arylpalladium amido species.
Thus, we prepared the arylpalladium amido complex containing
CyPF-t-Bu as ligand by an independent route from the correspond-
ing cationic arylpalladium complex of ammonia. Addition of AgOTf
to a solution of 1 and NH
MeOPh)(NH )]OTf, which was characterized as a 4:1 ratio of
stereoisomers by spectroscopic methods. A single crystal of one
isomer was obtained and was characterized by X-ray diffraction
methods (see Supporting Information). Deprotonation of this species
(
(
7) Huang, X. H.; Buchwald, S. L. Org. Lett. 2001, 3, 3417.
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8
31
(
b) Widenhoefer, R. A.; Buchwald, S. L. Organometallics 1996, 15, 3534.
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(
(
11) (a) Park, S.; Rheingold, A. L.; Roundhill, D. M. Organometallics 1991,
1
1
0, 615. (b) Casalnuovo, A. L.; Calabrese, J. C.; Milstein, D. Inorg. Chem.
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3 2 2
in CH Cl formed [Pd(CyPF-t-Bu)(4-
(
12) (a) Togni, A.; Breutel, C.; Schnyder, A.; Spindler, F.; Landert, H.; Tijani,
A. J. Am. Chem. Soc. 1994, 116, 4062. (b) Shen, Q.; Shekhar, S.; Stambuli,
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3
(
13) Stambuli, J. P.; Kuwano, R.; Hartwig, J. F. Angew. Chem., Int. Ed. 2002,
41, 4746.
by KN(SiMe
)
3 2
cleanly formed Pd(CyPF-t-Bu)(4-MeOPh)(NH
2
) as
(14) Shelby, Q.; Kataoka, N.; Mann, G.; Hartwig, J. F. J. Am. Chem. Soc.
2000, 122, 10718.
a 4:1 ratio of stereoisomers. This mixture of stereoisomers was
isolated in 40% yield after crystallization and was characterized
(
15) Stauffer, S.; Hauck, S. I.; Lee, S.; Stambuli, J.; Hartwig, J. F. Org. Lett.
2000, 2, 1423.
1
31
(16) Roy, A. H.; Hartwig, J. F. J. Am. Chem. Soc. 2003, 125, 8704.
by H and P NMR spectroscopy. Heating of this complex in the
presence of PPh to trap the Pd(0) product formed a 1:1 ratio of
3
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