Palladium-catalyzed intramolecular addition of amines to acetylenes. Synthesis of cyclic imines
摘要:
Intramolecular aminopalladation of alkynylamines gave intermediary alkenylpalladium compounds that hydrolyzed and isomerized to thermodynamically stable cyclic imines. Treatment of 3-alkynylamines with a catalytic amount of PdCl2(MeCN)2 gave exclusively 1-pyrrolines in good yields; 5-alkynylamines afforded 2,3,4,5-tetrahydropyridines selectively. Treatment of 4-alkynylamines with Pd(II) afforded mixtures of both 5- and 6-membered cyclic imines. Applications to the synthesis of some naturally occurring alkaloids are also described.
The cyclization of terminalalkynes with homopropargylicamines in the presence of a rhodium complex as catalyst leads to the formation of (E)-3-alkylidene-1-pyrrolines. The reaction tolerates a wide range of functional groups on the terminalalkynes. The formation of a vinylidene-rhodium complex, followed by the intermolecular nucleophilic attack of a homopropargylicamine nitrogen on the α-carbon