Base‐Catalyzed Anti‐Markovnikov Hydroamination of Vinylarenes – Scope, Limitations and Computational Studies

The hydroamination of vinylarenes with primary and secondary amines was studied with catalytic amounts as low as 2 mol‐% of LiN(SiMe 3 ) 2 /TMEDA. Reactions proceeded readily at 120 °C in the absence of solvent to give selective anti‐Markovnikov addition. Slow addition was observed at 25 °C with either electron‐deficient p ‐chlorostyrene or secondary cyclic amines such as pyrrolidine, piperidine, or morpholine. Primary amines were prone to a second hydroamination reaction to form tertiary amine byproducts. The selectivity for the mono(hydroamination) products could be improved with a two‐fold excess of the amine. KN(SiMe 3 ) 2 showed higher catalytic activity but lower selectivity in comparison to that of LiN(SiMe 3 ) 2 , resulting in undesired C–H‐activation byproducts. The mechanism of the lithium‐catalyzed hydroamination and the influence of TMEDA was studied with density functional theory. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)