Palladium-catalyzed alpha-arylation of tetramic acids.
A mild, racemization-free, palladium-catalyzed alpha-arylation of tetramic acids (2,4-pyrrolidinediones) has been developed. Various amino acid-derived tetramic acids were cleanly arylated by treatment with 2 mol % of Pd(OAc)(2), 4 mol % of a sterically demanding biaryl phosphine, 2.3 equiv of K(2)CO(3) or K(3)PO(4), and aryl chlorides, bromides, or triflates in THF. With conventional heating, conversions >95% could be attained after 1 h at 80 degrees C, whereas microwave-induced heating led to much shorter reaction times (5 min at 110 degrees C). The electron density of the aryl electrophile had no effect on their reactivity: both electron-rich and electron-poor aryl chlorides and bromides or triflates led to good yields. Ortho-substituted aryl halides and heteroaryl halides, however, did not undergo the title reaction.
Storgaard
Morten
M
Technical University of Denmark, Department of Chemistry, 201 Kemitorvet, DK-2800 Kgs. Lyngby, Denmark.
Dörwald
Florencio Zaragoza
FZ
Peschke
Bernd
B
Tanner
David
D
D002384:Catalysis; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010165:Palladium / Q000737:chemistry*; D011760:Pyrrolidinones / Q000737:chemistry*
D011760:Pyrrolidinones; C009435:tetramic acid; D010165:Palladium