acetone at 85 °C. Under this conditions, 91% of 3aa was
isolated with high chemo-, regio-, and stereoselectivities
(3aa/4aa ) 98:2; 3aa: internal/terminal >20:1, styrenyl/
allylic >20:1, E-3aa/Z-3aa ) 20:1) (entry 9, Table 1).
Gratifyingly, 78% of 3aa was formed when only 1 mol %
of Pd(OAc)2 was employed (entry 12, Table 1).
Table 2. Pd(OAc)2-Catalyzed Oxidative Heck Reaction of Allyl
Acetate 2a with Different Organoboronic Acids 1a
With the optimal reaction conditions in hand, we examined
the scope of the Pd(OAc)2-catalyzed oxidative Heck reaction
in the absence of ligand. A range of arylboronic acids with
electron-withdrawing or electron-donating groups proceeded
efficiently with good to excellent yields of the expected
arylated allyl acetates (Table 2). All reactions exhibited
excellent regioselectivities (internal/terminal >20:1, styrenyl/
allylic >20:1); no or only traces of allyl arene products 4
were observed in these transformations. Furthermore, the
stereoselectivities in some cases had been selectively con-
trolled (G20:1) for 3ca, 3da, 3ga, 3ha, 3ja, and 3oa. When
the arylboronic acids were substituted at the ortho position,
the yield was low due to the steric hindrance effect (entry 3,
Table 2). It is noteworthy that arylboronic acids with
substituents such as chlorides, nitriles, and aldehydes sur-
vived well (entries 8-10, 12, and 13, Table 2). Their
functional groups could thus be used for further transforma-
tions. Furthermore, arylboronic ester 1n smoothly provided
3da in 80% yield with high regioselectivities and stereose-
lectivity (entry 14). Notably, (2E,4E)-2,4-nonadienyl acetate
3oa was obtained in 37% yield when alkenylboronic ester
1o was employed in this transformation (entry 15, Table 2).
The scope of the ligand-free Pd(OAc)2-catalyzed highly
selective Heck reaction was further expanded to a variety
of substituted allyl esters 2 (Table 3). These results indicate
(5) (a) Ohmiya, H.; Makida, Y.; Tanaka, T.; Sawamura, M. J. Am. Chem.
Soc. 2008, 130, 17276–17277. For other oxidative Heck reactions of allyl
esters via ꢀ-OAc elimination, see: (b) Uozumi, Y.; Danjo, H.; Hayashi, T.
J. Org. Chem. 1999, 64, 3384–3388. (c) Miyaura, N.; Yamada, K.;
Suginome, Suzuli, A. J. Am. Chem. Soc. 1985, 107, 972–980. (d) Ramnauth,
J.; Poulin, O.; Rakhit, S.; Maddaford, S. P. Org. Lett. 2001, 3, 2013–2015.
(e) Legros, J.-Y.; Fiaud, J.-C. Tetrahedron Lett. 1990, 31, 7453–7456. (f)
Bouyssi, D.; Gerusz, V.; Balme, G. Eur. J. Org. Chem. 2002, 2445–2448.
For Heck reactions of allyl esters with aryl iodides via ꢀ-OAc elimination,
see: (g) Lautens, M.; Tayama, E.; Herse, C. J. Am. Chem. Soc. 2005, 127,
72–73. (h) Mariampillai, B.; Herse, C.; Lautens, M. Org. Lett. 2005, 7,
4745–4747.
a Reaction conditions: 1 (0.5 mmol), 2a (1.0 mmol), Pd(OAc)2 (0.025
mmol), AgOAc (1.0 mmol), CuF2 (0.5 mmol), KHF2 (1.0 mmol), acetone
(2.5 mL), in sealed tube, at 85 °C, 5 h. b E/Z determined by 1H NMR.
c Isolated yield.
(6) (a) Cheng, J. C.-Y.; Daves, G. D., Jr. Organometallics 1986, 5, 1753–
1755. (b) Zhu, G.; Lu, X. Organometallics 1995, 14, 4899–4904. (c) Zhang,
Q.; Lu, X. J. Am. Chem. Soc. 2000, 122, 7604–7605. (d) Lu, X. Top. Catal.
2005, 35, 73–86.
that the reaction is tolerant of a wide range of allyl acetates
substituted at the R- and ꢀ-positions. The regioselectivities
were also controlled in these transformations (internal/
terminal >20:1, styrenyl/allylic >20:1). Notably, allyl acetates
bearing H, Et, and pentyl groups, respectively, at the
R-position were efficiently performed with phenylboronic
acid (Table 2; entries 4 and 5, Table 3), despite the low yield
of R-methyl allyl acetate (entry 3, Table 3). Furthermore,
the stereoselectivities of these transformations with R-sub-
stituted allyl acetate were very high (only E-isomers were
observed, see entries 3-6). However, when the 2-position
of the substrate was substituted, the stereoselectivity became
worse due to the steric hindrance (entries 1 and 2, Table 3).
It is interesting to find that allyl benzoate 2h reacted with 1l
to give 3lh in 75% yield (entry 7). Moreover, E-3ai was
formed in 45% yield as the sole product when relatively
(7) Delcamp, J. H.; White, M. C. J. Am. Chem. Soc. 2006, 128, 15076–
15077.
(8) Ruan, J.; Li, X.; Saidi, O.; Xiao, J. J. Am. Chem. Soc. 2008, 130,
2424–2425.
(9) Pan, D.; Chen, A.; Su, Y.; Zhou, W.; Li, S.; Jia, W.; Xiao, J.; Liu,
Q.; Zhang, L.; Jiao, N. Angew. Chem., Int. Ed. 2008, 47, 4729–4732.
(10) (a) Beccalli, E. M.; Broggini, G.; Martinelli, M.; Sottocornola, S.
Chem. ReV. 2007, 107, 5318–5365. (b) Karabelas, K.; Westerlund, C.;
Hallberg, A. J. Org. Chem. 1985, 50, 3896–3900. (c) Madin, A.; Overman,
L. E. Tetrahedron Lett. 1992, 33, 4859–4862.
(11) This reaction was carried out under similar conditions developed
by White and co-workers (see ref 6) but employed 5 mol % of Pd(II)/
phenyl bis-sulfoxide as catalyst.
(12) (a) Ichikawa, J.; Moriya, T.; Sonoda, T.; Kobayashi, H. Chem. Lett.
1991, 961–964. (b) Wright, S. W.; Hageman, D. L.; McClure, L. D. J.
Org. Chem. 1994, 59, 6095–6097. (c) Littke, A. F.; Fu, G. C. Angew. Chem.,
Int. Ed. 1998, 37, 3387–3388. (d) Wolfe, J. P.; Buchwald, S. L. Angew.
Chem., Int. Ed. 1999, 38, 2413–2416. (e) Wolfe, J. P.; Singer, R. A.; Yang,
B. H.; Buchwald, S. L. J. Am. Chem. Soc. 1999, 121, 9550–9561. (f) Littke,
A. F.; Dai, C.; Fu, G. C. J. Am. Chem. Soc. 2000, 122, 4020–4028. (g)
Batey, R. A.; Quach, T. D. Tetrahedron Lett. 2001, 42, 9099–9103.
2982
Org. Lett., Vol. 11, No. 14, 2009