Novel Enantioselective Synthesis of Functionalized Pyridylarsanes by a ChiralPalladium Template Promoted Asymmetric Hydroarsanation Reaction

摘要

The asymmetric hydroarsanation reactions between di-phenylarsane and (E)-1-phenyl-3-(pyridin-2-yl)-2-propenoneand (E)-1-methyl-3-(pyridin-2-yl)-2-propenoate have beenachieved by use of the organopalladium complex containingortho-metalated (R)-[1-(dimethylamino)ethyl]naphthalene asthe chiral reaction template in high regio- and stereoselecti-vities under mild conditions. Hydroarsanation of (E)-1-phenyl-3- (pyridin-2-yl)-2-propenone with diphenylarsanegenerated two stereoisomeric products in the ratio of 3:1 asfive-membered As-N bidentate chelates on the chiral naph-thylamine palladium template. Using the same chiral metaltemplate, the corresponding hydroarsanation reaction with(E)-1-methyl-3-(pyridin-2-yl)-2-propenoate gave only one product as a six-membered As-N bidentate chelate. Thenaphthylamine auxiliary could be removed chemoselectivelyby treatment with concentrated hydrochloric acid to form thecorresponding optically pure neutral complexes. Subsequentligands displacement from the palladium using aqueous po-tassium cyanide generated the optically pure keto- and ester-functionalized chiral pyridylarsane ligands. The absoluteconfiguration and the coordination properties of the pyr-idylarsanes have been established by single-crystal X-rayanalysis.