SCHEME 1
Diamination of Conjugated Dienes and Trienes
Catalyzed by N-Heterocyclic Carbene-Pd(0)
Complexes
Liang Xu, Haifeng Du, and Yian Shi*
Department of Chemistry, Colorado State UniVersity,
Initial studies were carried out using 1-phenylbutadiene as
substrate. Several commercially available NHC-Pd complexes
4-9 listed in Figure 1 were examined for the diamination.9-11
Among these catalysts tested, (NHC)Pd(allyl)Cl complexes 4-7
were found to be effective for the diamination (Table 1). More
sterically hindered (IPr)Pd(allyl)Cl (4) gave a higher conversion
than IMesPd(allyl)Cl (5) (Table 1, entry 3 vs entry 8), suggesting
that the steric hindrance of NHC ligand plays an important role
in catalytic activity. One possible reason for this is that the steric
hindrance of NHC ligand may facilitate the reductive elimination
step in the catalytic cycle.1 Among the bases examined, sodium
tert-pentoxide (NaOtAm) was found to be most effective in
generating active NHC-Pd(0) catalyst from (NHC)Pd(allyl)Cl
precatalyst9 (Table 1, entries 1-3), possibly due to its good
solubility in organic solvent. The amount of base used was found
to be crucial, with 3 equiv with respect to Pd being optimal.
Using a greater or lesser amount of base led to a decrease in
yield. High conversion was obtained in solvents such as benzene,
toluene, and THF (Table 1, entries 3-5). High conversion was
also obtained without solvent (Table 1, entry 7) but with
somewhat diminished isolated yield, possibly due to the
polymerization of the diene under the reaction conditions. The
diamination was also investigated with in situ generated
NHC-Pd complexes from commercially available imidazolium
Fort Collins, Colorado 80523
ReceiVed May 5, 2007
This paper describes a diamination process using di-t-
butyldiaziridinone as nitrogen source and N-heterocyclic
carbene-Pd(0) complex as catalyst. A wide variety of
conjugated dienes and trienes can be effectively diaminated
in good yields with high regio- and stereoselectivities.
N-Heterocyclic carbenes (NHCs) have been shown to be
effective ligands for a variety of metal-catalyzed transforma-
tions.1 Compared to phosphines, carbene ligands usually form
more stable complexes with metals. Their electron richness and
steric bulkiness generally facilitate the oxidative addition and
reductive elimination processes which are fundamental steps
in many reactions.1 Recently, we reported a regio- and stereo-
selective diamination of conjugated dienes and trienes using
di-t-butyldiaziridinone as nitrogen source and Pd(PPh3)4 as
catalyst (Scheme 1).2,3-8 The unique features displayed by
carbene ligands prompted us to examine whether this transfor-
mation could also be effective using N-heterocyclic carbene-
Pd(0) complex as catalyst. Herein we report our preliminary
results on this subject.
(4) For examples of metal-mediated diaminations of olefins, see the
following. Co: (a) Becker, P. N.; White, M. A.; Bergman, R. G. J. Am.
Chem. Soc. 1980, 102, 5676. Hg: (b) Barluenga, J.; Alonso-Cires, L.;
Asensio, G. Synthesis 1979, 962. Mn: (c) Fristad, W. E.; Brandvold, T.
A.; Peterson, J. R.; Thompson, S. R. J. Org. Chem. 1985, 50, 3647. Os:
(d) Chong, A. O.; Oshima, K.; Sharpless, K. B. J. Am. Chem. Soc. 1977,
99, 3420. (e) Mun˜iz, K. Eur. J. Org. Chem. 2004, 2243. Pd: (f) Ba¨ckvall,
J.-E. Tetrahedron Lett. 1978, 163. Tl: (g) Aranda, V. G.; Barluenga, J.;
Aznar, F. Synthesis 1974, 504.
(5) For recent Cu(II)-mediated intramolecular diamination of olefins,
see: (a) Zabawa, T. P.; Kasi, D.; Chemler, S. R. J. Am. Chem. Soc. 2005,
127, 11250. (b) Zabawa, T. P.; Chemler, S. R. Org. Lett. 2007, 9, 2035.
(6) For Rh(II)- and Fe(III)-catalyzed diamination of olefins with TsNCl2,
see: (a) Li, G.; Wei, H.-X.; Kim, S. H.; Carducci, M. D. Angew. Chem.
Int. Ed. 2001, 40, 4277. (b) Wei, H.-X.; Kim, S. H.; Li, G. J. Org. Chem.
2002, 67, 4777.
(7) For a recent Pd(II)-catalyzed intermolecular diamination of conjugated
dienes, see: Bar, G. L. J.; Lloyd-Jones, G. C.; Booker-Milburn, K. I. J.
Am. Chem. Soc. 2005, 127, 7308.
(8) For a recent Pd(II)-catalyzed intramolecular diamination of terminal
olefins, see: Streuff, J.; Ho¨velmann, C. H.; Nieger, M.; Mun˜iz, K. J. Am.
Chem. Soc. 2005, 127, 14586.
(9) For leading references on complexes 4-7, see: (a) Viciu, M. S.;
Germaneau, R. F.; Navarro-Fernandez, O.; Stevens, E. D.; Nolan, S. P.
Organometallics 2002, 21, 5470. (b) Marion, N.; Navarro, O.; Mei, J.;
Stevens, E. D.; Scott, N. M.; Nolan, S. P. J. Am. Chem. Soc. 2006, 128,
4101.
(10) For leading references on complex 8, see: (a) O’Brien, C. J.;
Kantchev, E. A. B.; Valente, C.; Hadei, N.; Chass, G. A.; Lough, A.;
Hopkinson, A. C.; Organ, M. G. Chem. Eur. J. 2000, 12, 4743. (b) Organ,
M. G.; Abdel-Hadi, M.; Avola, S.; Hadei, N.; Nasielski, J.; O’Brien, C. J.;
Valente, C. Chem. Eur. J. 2007, 13, 150.
* To whom correspondence should be addressed. Phone: 970-491-7424.
Fax: 970-491-1801.
(1) For leading reviews, see: (a) Herrmann, W. A. Angew. Chem., Int.
Ed. 2002, 41, 1290. (b) Hillier, A. C.; Grasa, G. A.; Viciu, M. S.; Lee, H.
M.; Yang, C.; Nolan, S. P. J. Organomet. Chem. 2002, 653, 69. (c) Ce´sar,
V.; Bellemin-Laponnaz, S.; Gade, L. H. Chem. Soc. ReV. 2004, 33, 619.
(d) Bedford, R. B.; Cazin, C. S. J.; Holder, D. Coord. Chem. ReV. 2004,
248, 2283. (e) Christmann, U.; Vilar, R. Angew. Chem., Int. Ed. 2005, 44,
366. (f) Crabtree, R. H. J. Organomet. Chem. 2005, 690, 5451. (g) Kantchev,
E. A. B.; O’Brien, C. J.; Organ, M. G. Aldrichim. Acta 2006, 39, 97. (h)
Hahn, F. E. Angew. Chem., Int. Ed. 2006, 45, 1348. (i) Nolan, S. P.
N-Heterocyclic Carbenes in Synthesis; Wiley-VCH: Weinheim, Germany,
2006. (j) Glorius, F. N-Heterocyclic Carbenes in Transition Metal Catalysis;
Springer: Berlin, 2007.
(2) Du, H.; Zhao, B.; Shi, Y. J. Am. Chem. Soc. 2007, 129, 762.
(3) For leading reviews on diamination, see: (a) Lucet, D.; Gall, T. L.;
Mioskowski, C. Angew. Chem., Int. Ed. 1998, 37, 2580. (b) Mortensen, M.
S.; O’Doherty, G. A. Chemtracts: Org. Chem. 2005, 18, 555. (c) Kotti, S.
R. S. S.; Timmons, C.; Li, G. Chem. Biol. Drug. Des. 2006, 67, 101.
(11) For leading references on complex 9, see: (a) Selvakumar, K.; Zapf,
A.; Spannenberg, A.; Beller, M. Chem. Eur. J. 2002, 8, 3901. (b)
Selvakumar, K.; Zapf, A.; Beller, M. Org. Lett. 2002, 4, 3031.
10.1021/jo0709394 CCC: $37.00 © 2007 American Chemical Society
Published on Web 08/04/2007
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J. Org. Chem. 2007, 72, 7038-7041