Fluorine-Containing Allenylpalladium Complexes. Synthesis of Optically Active Fluoroalkylated Allenes and Furan Derivatives

Abstract

The reaction of fluoroalkylated propargyl mesylates with various nucleophiles, such as zinc reagents and enolates derived from 1,3-dicarbonyl compounds, in the presence of a palladium catalyst was investigated in detail. Various zinc reagents participated in the coupling reaction to give the corresponding fluoroalkylated allenes in good yields. When chiral mesylates were employed, the corresponding optically active allenes were obtained without any loss of enantiomeric purity in the reaction. On the other hand, treatment of trifluoromethylated propargyl mesylate with stabilized carbanions derived from methyl acetoacetate, acetylacetone, and diethyl malonate afforded fluorine-containing furan derivatives in moderate to high yields.Transition metals are able to catalyze a wide range of synthetically useful organic reactions, very often with high levels of chemo-and stereoselectivity 1 . In particular, palladium-catalyzed reactions have been employed with success in a number of important chemical processes, such as Stille coupling 2 , Suzuki coupling 3 , Negishi coupling 4 , Heck reactions 5 , and allylic substitution 6 .Palladium-catalyzed reactions of propargylic compounds have also been investigated in considerable detail over the last twenty years, and are considered as some of the most valuable synthetic reactions 7 . In sharp contrast to these investigations, palladium-catalyzed transformations of fluorine-

Allenyl Azide Cycloaddition Chemistry. Synthesis of Pyrrolidine-Containing Bicycles and Tricycles via the Possible Intermediacy of Azatrimethylenemethane Species

“…Scouting experiments to test this plan began with the phenyl-substituted allenyl azide 1a , available from the acrolein azide addition product 7 7 in a few well-precedented steps (Scheme ) …”