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F. Bellina, R. Rossi
PAPER
IR (KBr): 1750, 1660, 1452, 1338, 1169, 1073, 1054, 1007 cm–1.
1H NMR (CDCl3): = 1.10 (d, 6 H, J = 7.0 Hz), 3.06 (hept, 1 H,
J = 7.0 Hz), 3.62 (s, 2 H), 4.71 (s, 2 H), 7.21 (m, 5 H).
13C NMR (CDCl3): = 20.9 (2 C), 27.2, 29.4, 68.7, 124.3, 126.3,
128.3 (2 C), 128.4 (2 C), 138.1, 166.8, 174.9.
(6) Evidente, A.; Randazzo, G.; Ballio, A. J. Nat. Prod. 1986,
49, 593.
(7) For reviews on the synthesis of stereodefined 5-ylidene-
2(5H)-furanones, see: (a) Negishi, E.-I.; Kotora, M.
Tetrahedron 1997, 53, 6707. (b) Brückner, R. Curr. Org.
Chem. 2001, 5, 679. (c) Brückner, R. Chem. Commun. 2001,
141. (d) Rossi, R.; Bellina, F. Targets in Heterocyclic
Systems: Chemistry and Properties 2002, 5, 169.
(8) Bellina, F.; Rossi, R.; Abstracts from Transmediterranean
Colloquium on Heterocyclic Chemistry: Bari Italy June 20–
24, 2002.
(9) Yang, X.; Shimizu, Y.; Steiner, J. R.; Clardy, J. Tetrahedron
Lett. 1993, 34, 761.
(10) Boukouvalas, J.; Maltais, F.; Lachance, N. Tetrahedron Lett.
1994, 35, 7897.
MS: m/z (%) = 216 (14), 173 (37), 155 (16), 129 (100), 128 (23),
115 (21), 91 (30).
3-Benzyl-4-isopropenyl-2(5H)-furanone (21)
To a solution of 3-bromo-4-isopropenyl-2(5H)-furanone (19; 0.30
g, 1.5 mmol), Pd2(Pdba)3 (0.03 g, 0.04 mmol), (2-furyl)3P (0.04 g,
0.15 mmol) and CuI (0.03 g, 0.15 mmol) in NMP (5 mL) was added
a solution of benzyltributyltin (23; 0.73 g, 1.92 mmol) in NMP (2
mL), and the resulting mixture was refluxed for 45 h. The mixture
was poured into a sat. aq NH4Cl solution (100 mL) and extracted
with EtOAc (4 20 mL). The combined organic extracts were then
stirred for 6 h at r.t. with an aq 50% KF solution (100 mL), filtered
over Celite and the filtrate was extracted with EtOAc (4 10 mL).
The combined organic extracts were washed with brine (4 30
mL), dried (Na2SO4), filtered and concentrated under reduced pres-
sure to furnish a reddish viscous oil, which was purified by MPLC
on silica gel with CH2Cl2–petroleum ether (60:40 + 1% EtOAc) as
eluent. The chromatographic fractions containing the required com-
pound were concentrated under reduced pressure to give pure 21 as
an orange oil; yield 0.07 g (22%, 95% purity by GC).
(11) This compound was prepared according to a procedure
reported in the literature: Snyder, H. R.; Kuch, J. A.;
Johnson, J. R. J. Am. Chem. Soc. 1938, 60, 105.
(12) Ngwe, H.; Nakayama, E.; Higashi, T.; Kinoshita, H.;
Inomata, K. Chem. Lett. 1995, 713.
(13) It should be noted that when we attempted to prepare 8a by
hydrogenation of 18 in toluene at r.t. in the presence of 10
mol% Pd on BaSO4, the reaction provided significant
amounts of a compound which had a MS spectrum
corresponding to that of 4-isopropyl-2(5H)-furanone.
(14) The catalyst precursor constiting of Pd2(dba)3 (2.5 mol%)/
(o-Tol)3P (10 mol%) gave a similar yield, while the use of
Pd2(dba)3 (2.5 mol%)/Ph3As (10 mol%) or Pd(PPh3)4 (5
mol%) as catalyst precursors gave less satisfactory results.
(15) For previous examples of Pd-catalyzed reactions between
Csp2-hybridized halides and benzylzinc halides, see:
(a) Negishi, E.-i.; Tan, Z.; Liou, S.-Y.; Liao, B. Tetrahedron
2000, 56, 10197. (b) Gundersen, L.-L.; Langli, G.; Rise, F.
Tetrahedron Lett. 1995, 36, 1945. (c) Gundersen, L.-L.;
Bakkestuen, A. K.; Aasen, J.; Overas, H.; Rise, F.
Tetrahedron 1994, 50, 9743. (d) Moriya, T.; Miyaura, N.;
Suzuki, A. Chem. Lett. 1993, 1429. (e) Negishi, E.-i.; King,
A. O.; Okukado, N. J. Org. Chem. 1977, 42, 1821.
(16) It should be noted that the crude product, derived from the
Pd-catalyzed reaction of 8a with 20, contained compound 14
and significant amounts of 1,2-diphenylethane (22) and a
compound which had a MS spectrum in agreement with that
of 3,5-dibenzyl-4-isopropyl-2(5H)-furanone.
1H NMR (CDCl3): = 2.04 (m, 3 H), 3.83 (s, 2 H), 4.87 (s, 2 H),
5.24 (m, 1 H), 5.30 (m, 1 H), 7.21 (m 5 H).
13C NMR (CDCl3): = 21.6, 30.1, 74.5, 120.0, 125.5, 126.3, 128.1
(2 C), 128.5 (2 C), 136.0, 138.0, 157.0, 175.1.
MS: m/z (%) = 214 (80), 169 (100), 153 (40), 141 (76), 129 (78),
115 (51), 91 (68).
Anal. Calcd for C14H14O2: C, 78.48; H, 6.58. Found: C, 78.63; H,
6.65.
Acknowledgment
This work was supported by the Ministero dell’Istruzione, dell’Uni-
versità e della Ricerca (MIUR) and the University of Pisa.
References
The use of PdCl2[(o-Tol)3P]2 (5 mol%)/CuI (10 mol%),
Pd2(dba)3 (2.5 mol%)/Ph3As (10 mol%)/CuI (10 mol%) or
Pd2(dba)3 (2.5 mol%)/t-Bu3P (10 mol%)/CuI (10 mol%) as
catalyst precursors in NMP at 85 °C gave less satisfactory
results, while employing Pd2(dba)3 (2.5 mol%)/t-Bu3P (10
mol%) as a catalyst precursor in dioxane at reflux and in the
presence of 3 equiv of KF no product was obtained.
(17) (a) Chuang, C.; Gallucci, J. C.; Hart, D. J.; Hoffmann, C. J.
Org. Chem. 1988, 53, 3218. (b) Labadie, J. W.; Tueting, D.;
Stille, J. K. J. Org. Chem. 1983, 48, 4634.
(1) Rossi, R.; Bellina, F.; Raugei, E. Synlett 2000, 1749.
(2) Bellina, F.; Anselmi, C.; Rossi, R. Tetrahedron Lett. 2002,
43, 2023.
(3) Bellina, F.; Anselmi, C.; Viel, S.; Mannina, L.; Rossi, R.
Tetrahedron 2001, 57, 9997.
(4) Bellina, F.; Anselmi, C.; Rossi, R. Tetrahedron Lett. 2001,
42, 3851.
(5) Ortega, M. J.; Zubía, E.; Ocaña, J. M.; Naranjo, S.; Salvá, J.
Tetrahedron 2000, 56, 3963.
(18) Desponds, O.; Schlosser, M. J. Organomet. Chem. 1991,
409, 93.
Synthesis 2002, No. 18, 2729–2732 ISSN 0039-7881 © Thieme Stuttgart · New York