Received September 8, 1999

Abstract:

Reaction of 1,3-dicyanobenzene with -amino alcohols (S)-H₂NCHRCH₂OH (R = ⁱPr, ⁱBu, ^tBu, CH₂Cy, CH₂Ph) and (R)-H₂NCHPhCH₂OH gave new 1,3-bis(2'-oxazolinyl)benzenes (30-51%). These, together with 1,3-bis(4',4'-dimethyl-2'-oxazolinyl)benzene, were treated with LDA/TMEDA followed by the addition of PdBr₂(1,5-COD) to give [2,6-bis(2'-oxazolinyl)phenyl]palladium(II) bromide complexes (21-41%). In two cases no complexes were obtained (R = Ph, CH₂Ph) due to ring opening of the oxazolines by LDA/TMEDA. Treatment of the palladium complexes with AgBF₄, AgOTf, or AgSbF₆ in wet CH₂Cl₂ provided a series of cationic [2,6-bis(2'-oxazolinyl)phenyl]palladium complexes (28-87%) containing water coordinated to palladium, as established by an X-ray crystal structure analysis of (S,S)-[2,6-bis(4'-isopropyl-2'-oxazolinyl)phenyl]aquopalladium(II) trifluoromethanesulfonate. All of the cationic complexes proved to be efficient catalysts for the Michael reaction between -cyanocarboxylates and methyl vinyl ketone and between acrylonitrile and activated Michael donors. Selectivities of up to 34% ee were obtained for the formation of (R)-ethyl 2-cyano-2-methyl-5-oxohexanoate.

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