1860
V. Maslak et al. / Tetrahedron Letters 50 (2009) 1858–1860
Table 1 (continued)
Entry
Reactants
Conditions
Products
Yields (%)
O
B
O
O
O
17
18
OP(OEt)2
G
72
+
K
OMe
MeO
O
O
B
O
+
K
OP(OEt)2
O
G
H
40
40
Cl
Cl
Negishi coupling
O
ZnCl
OP(OEt)2
19
Reagents and conditions:
(A) Pd(OAc)2 (10 mol %), PPh3 (20 mol %), TBAF (200 mol %), DMF, Ar, 90 °C, 24 h;
(B) Pd(OAc)2 (10 mol %), PPh3 (20 mol %), TBAF (200 mol %), DMF, Ar, mw, 300 W, 25 min (120 °C);
(C) Pd(dba)2 (5 mol %), LiCl (300 mol %), DMF, Ar, rt, 24 h;
(D) Pd(dba)2 (1 mol %), CyJohnPhos (4 mol %), K3PO4Á3H2O (200 mol %), toluene, Ar, 90 °C, 16 h;
(E) Pd(dba)2 (1 mol %), K3PO4Á3H2O (200 mol %), toluene, Ar, mw, 300 W, 25 min (120 °C);
(F) Pd(dba)2 (1 mol %), XPhos (4 mol %), K3PO4 anhyd (200 mol %), toluene, Ar, 90 °C, 45 min;
(G) Pd(OAc)2 (5 mol %), DMF, H2O, rt, 2 h;
(H) Pd2dba3 (2.5 mol %), dppf (5 mol %), THF, 70 °C, 16 h.
the geranylation of phenols, a transformation that was previously
performed under strongly acidic conditions where side reactions
were also possible.12 Finally, the formation of cinnamyl benzene
in the reaction of cinnamyl phosphate with phenylzinc chloride
showed that allylic phosphates could serve as reaction partners
for the Negishi coupling, although the yield in this reaction was
not high (entry 19).
Couplings were also performed under microwave irradiation,
which brought about a significant shortening of the reaction times,
with the yields comparable to those obtained with conventional
heating.13 For example, the Hiyama coupling, which required
24 h at 90 °C, was complete within 25 min under mw irradiation
(entry 2; see also entries 9 and 11).
References and notes
1. For a comprehensive review, see: Handbook of Organopalladium Chemistry for
Organic Synthesis; Negishi, E.-i., de Meijere, A., Eds.; John Wiley & Sons: New
York, 2002; Vol. 2, Chapter V, pp 1669–1844.
2. McLaughlin, M. Org. Lett. 2005, 7, 4875–4878.
3. Kofink, C. C.; Knochel, P. Org. Lett. 2006, 8, 4121–4124.
4. Dunet, G.; Knochel, P. Synlett 2007, 1383–1386.
5. (a) Kimura, M.; Yamazaki, T.; Kitazume, T.; Kubota, T. Org. Lett. 2004, 6, 4651–
4654; (b) Rodriguez, D.; Sestelo, J. P.; Sarandeses, L. A. J. Org. Chem. 2003, 68,
2518–2520.
6. Shvo, Y.; Arisha, A. H. I. J. Org. Chem. 2001, 66, 4921–4922.
7. Murahashi, S.-I.; Imada, Y.; Taniguchi, Y.; Higashiura, S. J. Org. Chem. 1993, 58,
1538–1545.
8. (a) Miller, J. A.; Wood, H. C. S. J. Chem. Soc. C 1968, 1837–1843; (b) Nowotny, S.;
Tucker, C. E.; Jubert, C.; Knochel, P. J. Org. Chem. 1995, 60, 2762–2772.
9. Mowery, M. E.; DeShong, P. Org. Lett. 1999, 1, 2137–2140.
10. Del Valle, L.; Stille, J. K.; Hegedus, L. S. J. Org. Chem. 1990, 55, 3019–3023.
11. Yamamoto, Y.; Takizawa, M.; Xiao-Qiang, Y.; Miyaura, N. Angew. Chem., Int. Ed.
2008, 47, 928–931.
12. (a) Araki, S.; Manabe, S.-i.; Butsugan, Y. Chem. Lett. 1982, 797–800; (b) Malkov,
A.; Spoor, P.; Vinader, V.; Kocovsky, P. J. Org. Chem. 1999, 64, 5308–5311; c See
also Ref. 4
To summarize, allylic phosphates can be used as electrophiles in
a range of palladium-catalyzed cross-couplings. The straightfor-
ward preparation of these derivatives from the corresponding alco-
hols, coupled with their good reactivity, makes them potentially
useful precursors for cross coupling reactions.
13. Typical experimental procedure (Suzuki coupling):
A 12 mL glass tube was
charged with cinnamyl phosphate (100 mg; 0.37 mmol), phenylboronic acid
(54 mg; 0.44 mmol), K3PO4 Á 2H2O (131 mg; 56 mmol), Pd2(dba)3 (11 mg,
5 mol %), toluene (3 mL), and a piece of Weflon. This tube was placed in a
Teflon outer jacket and secured with a Teflon top containing a ceramic thermo
well, with the fiber-optic probe inside. The sample was irradiated for 5 min
(multimode type irradiation) with 300 W power, in order to reach 120 °C, and
was maintained at that temperature for 20 min more, with magnetic stirring.
The reaction mixture was then cooled to room temperature, diluted with
diethyl ether, and filtered through a cotton plug. The organic extract was
washed with water, dried over anhydrous MgSO4, filtered, concentrated under
reduced pressure, and purified by column chromatography on SiO2, to provide
Acknowledgment
This research was supported by the Serbian Ministry of Science
(Project No. 142021).
Supplementary data
Detailed experimental procedures and the complete spectral
data of all new compounds are provided. Supplementary data asso-
ciated with this article can be found, in the online version, at
50 mg (72%) of (E)-1,3-diphenylpropene as
a colorless oil, spectral data
identical to previously reported in: Baker, L.; Minehan, T. J. Org. Chem. 2004,
69, 3957–3960; Correia, R.; DeShong, P. J. Org. Chem. 2001, 66, 7159–7165, and
Lawrence, N. J.; Muhammad, F. Tetrahedron 1998, 54, 15345–15360.