Group‐IV Metal Complexes as Hydroamination Catalysts

Abstract

During the last 50 years, group‐IV metal complexes have been used extensively as catalysts in organic chemistry. However, a new and rapidly growing field for group‐IV metal catalysis evolved in the 1990s when the groups of Bergman, Livinghouse and Doye found that zirconium and titanium complexes catalyze the inter‐ and intramolecular hydroamination of alkynes and allenes. Starting from early results obtained with zirconocene bis(amides), this review deals mostly with hydroamination reactions based on titanium catalysts. In this context, studies directed towards catalyst development are presented as well as applications of corresponding processes for the synthesis of biologically interesting compounds. However, the Microreview covers group‐IV metal complex catalyzed hydroamination reactions of alkynes and allenes that appeared in the literature before July 31, 2002. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Titankatalysierte Hydroaminoalkylierung von Alkenen durch C‐H‐Aktivierung an sp3‐Zentren in der α‐Position zum Stickstoffatom

“…Neben anderen Metallkatalysatoren [1] kamen für die genannten Reaktionen auch unterschiedlichste Ti-Katalysatoren zum Einsatz. [2][3][4] Bei einer Studie zur Ti-katalysierten intramolekularen Hydroaminierung von Alkenen stellten wir kürzlich fest, dass die Cyclisierung von 1-Amino-5-hexenen zu Piperidinen (Schema 1) in Gegenwart von [Ti(NMe 2 ) 4 ] und [Ind 2 TiMe 2 ] (Ind = Indenyl) unter Bildung von Cyclopentylamin-Nebenprodukten verläuft.…”

Development of a Q2MM Force Field for the Silver(I)‐Catalyzed Hydroamination of Alkynes

“…A promising strategy towards such heterocycles is the intramolecular hydroamination of alkenes and alkynes by an amine or amine derivative. Many different metal catalysts have been investigated for hydroamination of alkenes and alkynes, including lanthanides, [10] transition metals, [11] and some alkali earth metals. [12] Recently, we demonstrated the efficient catalysis of intramolecular hydroaminations of alkynes by silver 1,10-phenanthroline complexes.…”

Hydroamination/Hydrosilylation Sequence Catalyzed by Titanium Complexes

“…[2] During the last few years, we have been intensively involved in the development of the Ti-catalyzed hydroamination of alkynes, which converts alkynes and primary amines into imines in the presence of Ti IV catalysts. [3] The corresponding imine products were usually reduced with stoichiometric amounts of NaBH 3 CN to give secondary amines. Herein, for the first time, we describe a sequential combination of the Ti-catalyzed hydroamination of alkynes with the Ti-catalyzed reduction of imines.…”

“…In these cases, under the employed reaction conditions, the desired secondary amines could be isolated in only modest to poor yields, even when the reaction time for the hydrosilylation was extended to 48 h. [7] Since the regioselectivity of the reaction sequence is generally determined during the hydroamination step, the ratios of the regioisomeric secondary amines are very good to excellent, as expected. [3] Additionally, two reaction sequences were performed with the ansa complex 22 [8] as the precatalyst (entries 5,11). Both reactions also led to the formation of the desired secondary amines.…”