LETTER
Heck Arylation of Maleic Anhydrides Using Arenediazonium Tetrafluoroborates
3149
MeO
OH
OMe
(5) (a) Dean, W. D.; Blum, D. M. J. Org. Chem. 1993, 58, 7916.
b) Newman, M. S.; Stalick, W. M. J. Org. Chem. 1973, 38,
386.
(
3
MeO
OMe
O
(
(
6) Koelsch, C. F.; Wawzonek, S. J. Org. Chem. 1941, 6, 684.
7) Gupta, A. K.; Song, C. H.; Oh, C. H. Tetrahedron Lett. 2004,
45, 4113.
NH2
O
O
N
(
8) Dubernet, M.; Caubert, V.; Guillard, J.; Viaud-Massuard, M.
C. Tetrahedron 2005, 61, 4585.
O
O
C6H6, Et3N, reflux,
molecular sieves, 24 h
O
HO
3
O
(9) (a) For a review, see: Rondestvedt, C. S. Org. React. 1976,
4, 225. (b) Nikitin, K. V.; Andryukhova, N. P. Chem.
fluorescent green
2
Heterocycl. Compd. 2004, 40, 561. (c) Rondestvedt, C. S.;
Vogl, O. J. Am. Chem. Soc. 1955, 77, 2313.
10) (a) Pastre, J. C.; Correia, C. R. D. Org. Lett. 2006, 8, 1657.
7
(
(
fluorescent yellow
0% (not optimized)
(b) Unpublished results extending those reported in ref. 10a.
5
11) Reactions using Pd (dba) as catalyst generate a number of
2
3
colored side products, probably due to the Heck arylation of
the ligand dba. A better Pd(0) source was obtained by in situ
Scheme 5 Synthesis of a N-protected and fluorescent phenylalanine
reduction of Pd(OAc) using dihydrofuran, and anisole as
2
additive. This procedure provided a finely dispersed Pd(0) in
MeCN (see ref. 17). Arylation failed with other bases, such
with the syntheses of prepolycitrin A (5), polycitrin A (6),
and of the fluorescent N-protected phenylalanine 7. Fur-
ther studies aiming at extending these Heck arylations to
a more diverse class of arylated maleic anhydrides as well
as new applications for the fluorescent materials prepared
herein are in progress and will be reported in due course.
as: 2,6-di(tert-butyl)-4-methylpyridine, Et N, imidazole,
3
K CO and BaCO .
2
3
3
(12) Superstoichiometric amount of the arenediazonium salts (2
or 4 equiv) is not strictly required for the synthesis of the
diarylated adducts. However, the use of excess of this
reagent leads to shorter reaction times and higher yields.
(
(
(
13) Terpin, A.; Polborn, K.; Steglich, W. Tetrahedron 1995, 51,
9941.
14) Beccalli, E. M.; Clerici, F.; Marchesini, A. Tetrahedron
Acknowledgment
We thank FAPESP (Research Supporting Foundation of the State of
São Paulo) and CAPES for financial support and fellowship.
2000, 56, 2699.
15) Pal, M.; Swamy, N. K.; Hameed, P. S.; Padakanti, S.;
Yeleswarapu, K. R. Tetrahedron 2004, 60, 3987.
16) Bertozzi, C. R.; Prescher, J. A. Nat. Chem. Biol. 2005, 1, 13.
17) Typical Experimental Procedure.
(
(
References and Notes
To a solution of 4.5 mg of Pd(OAc) in 3 mL of MeCN was
(
(
(
1) Rudi, A.; Evan, T.; Aknin, M.; Kashman, Y. J. Nat. Prod.
2
added anisole (0.8 mL of a 0.1 M solution in MeCN) and 2,3-
dihydrofuran (0.2 mL of a 0.1 M solution in MeCN). After 5
min, 49 mg of maleic anhydride (0.5 mmol), 123 mg of
NaOAc (1.5 mmol) and 443 mg of 4-methoxybenzene-
diazonium tetrafluoroborate (2 mmol) were added and the
reaction mixture refluxed for 1 h. After cooling, the reaction
mixture was diluted with 15 mL of EtOAc and filtered
2000, 63, 832.
2) Rudi, A.; Golberg, I.; Stein, Z.; Frolow, F.; Benayahu, Y.;
Schleyer, M.; Kashman, Y. J. Org. Chem. 1994, 59, 999.
3) (a) Chen, C.; Yeh, H.; Wu, W. Chem. Commun. 2003, 404.
(
b) Fields, E. K.; Behrend, S. J.; Meyerson, S.; Winzenburg,
M. L.; Ortega, B. R.; Hall, H. K. J. Org. Chem. 1990, 55,
165.
5
®
through a short pad of Celite . The solvent was then
(
4) (a) Hargreaves, M. K.; Pritchard, J. G.; Dave, H. R. Chem.
Rev. 1970, 70, 439. (b) Cava, M. P.; Deana, A. A.; Muth, K.;
Mitchell, A. J. Org. Synth., Coll. Vol. V 1973, 944.
evaporated in vacuo and the residue flash chromatographed
(
SiO , hexane–EtOAc = 8:2) to provide 93 mg (60% yield)
2
of the Heck adduct 3 as homogeneous material by TLC.
Synlett 2006, No. 18, 3145–3149 © Thieme Stuttgart · New York