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(SiMe3)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(SiMe3)2 showed higher catalytic activity but lower selectivity in comparison to that of LiN(SiMe3)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)