Gold(I) and Platinum(II)-Catalyzed Hydrofunctionalization of Allenes and Alkenes with Carbon and Nitrogen Nucleophiles

Abstract

The wide-spread occurrence of biologically active nitrogen-containing heterocycles and allylic amines inspired us to develop atom-economical methods for their syntheses.A cationic gold(I) N-heterocyclic carbene complex catalyzed the intermolecular hydroarylation of allenes with indoles to form (E)-allylic indoles in modest to good yield at room temperature. The protocol was effective for monosubstituted, 1,3-disubstituted, and tetrasubstituted allenes and various indoles. Platinum(II) bis(phosphine) complexes catalyzed the intermolecular hydroamination of monosubstituted allenes with secondary alkylamines in good yield with selective formation of (E)-allylic amines. The scope of the protocol included aryl and alkyl monosubstituted allenes as well as a variety of both cyclic and acyclic secondary alkylamines.The scope of gold(I)-catalyzed intermolecular hydroamination of 1-alkenes with 1-methyl-2-imidazolidinone was expanded to include additional 1-alkenes functionalized with carboxylic acid derivatives. However, a nucleophile screen failed to identify nucleophiles other than cyclic ureas and 2-oxazolidinone that efficiently undergo hydroamination with 1-alkenes. Various carbamates, arylamines, amide derivatives, sulfur-containing amide derivatives, and α-heteroatom compounds failed to react with 1-octene under gold(I)-catalyzed conditions.A chiral bis(gold) phosphine complex catalyzed the stereoconvergent, intermolecular enantioselective hydroamination of chiral, racemic 1,3-disubstituted allenes with carbamates to form N-allylic carbamates in good to high yield with up to 92% ee. In addition, enantiopurity experiments suggested the nature of the catalytically active species changes with increasing concentration of N-allylic carbamate.