Asymmetric Palladium-Catalyzed Annulation of Benzene-1,2-diol and Racemic Secondary Propargylic Carbonates Bearing Two Different Substituents

Autor: Boguslaw Kryczka, Celine Damez, Jean-Robert Labrosse, Norbert Dominczak, Bouchra Rhers, Denis Sinou, Paul Lhoste
Rok vydání: 2005
Předmět:
Zdroj: ChemInform. 36
ISSN: 1522-2667
0931-7597
DOI: 10.1002/chin.200529161
Popis: The palladium-catalyzed cyclization of benzene-1,2-diol with various racemic secondary propargyl carbonates having no acetylenic hydrogen in the presence of (R)-Binap as the chiral ligand afforded the two regioisomers of the corresponding 2,3-dihydro-1,4-dioxin derivatives in quite good yields, and also in enantioselectivities going from 40 to 97%. The cyclization of benzene-1,2-diol with methyl (R)-1-methyl-3-phenylpro-2-yn-1-yl carbonate in the presence of dppb as the achiral ligand afforded 2-benzylidene-3-methyl-2,3-dihydro-1,4-benzodioxine as the major product with 15% ee. The use of (R)-Binap as the chiral ligand afforded the (+) cyclized compound in 45% ee, when the (−) enantiomer was obtained with 77% ee in the presence of (S)-Binap. All the results suggest that in this case the enantioselective step is the diastereoselective protonation of the palladium–carbene intermediates.
Databáze: OpenAIRE
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