Preparation of Half-Sandwich Alkyl−Titanium(IV) Complexes Stabilized by a Cyclopentadienyl Ligand with a Pendant Phosphine Tether and Their Use in the Catalytic Hydroamination of Aliphatic and Aromatic Alkynes

Rhodium-Catalyzed Anti-Markovnikov Hydroamination of Aliphatic and Aromatic Terminal Alkynes with Aliphatic Primary Amines

Anti-Markovnikov hydroamination of both aliphatic and aromatic terminal alkynes with primary amines was achieved using an 8-quinolinolato rhodium catalyst to form aldimines and enamines in high yields. This catalytic system realized high functional group tolerance including hydroxy, bromo, cyano, and thioester groups.

Titanium catalysis for the synthesis of fine chemicals – development and trends

Atlas as a Titan(ium) is holding the earth-abundant chemistry world. Titanium is the second most abundant transition metal, is a key player in important industrial processes (e.g. polyethylene) and shows much promise for diverse applications in the future.

Gold(i) catalysed regio- and stereoselective intermolecular hydroamination of internal alkynes: towards functionalised azoles

Vinyl- and saturated azoles were synthesised through gold(i) catalysed regio- and stereoselective intermolecular hydroamination of internal alkynes and subsequent hydrogenation.

Construction of regio- and stereoregular poly(enaminone)s by multicomponent tandem polymerizations of diynes, diaroyl chloride and primary amines

An atom-economical multicomponent tandem polymerization was developed to afford multifunctional regio- and stereoregular conjugated poly(enaminone)s.

A new facile synthesis of 3-amidoindole derivatives and their evaluation as potential GSK-3beta inhibitors

3-Amidoindoles were synthesized from commercially available arylhydrazines and propargylamines over Zn-salt mediated one pot procedure in excellent regioselectivity and up to 94% yield.

Titanium hydroamination catalysts bearing a 2-aminopyrrolinato spectator ligand: monitoring the individual reaction steps

A series of new titanium half sandwich complexes, containing a 2-aminopyrrolinato ligand {N(Xyl)N}(-) as the ancillary ligand, have been prepared and are shown to be pre-catalysts for the hydroamination of alkynes. The coordination of {N(Xyl)N}(-) to titanium was achieved by reaction of [Cp*TiMe(3)] with the protioligand N(Xyl)NH giving [Cp*Ti(N(Xyl)N)(Me)(2)] (). Upon reaction of complex with an excess of tert-butylamine, the imido complex [Cp*Ti(N(Xyl)N)(N(t)Bu)(NH(2)(t)Bu)] () was formed. The latter provided the preparative entry to the synthesis of a range of N-aryl substituted imido complexes. Imido ligand exchange with 2,6-dimethylaniline, 2,4,6-trimethylaniline as well as 2,6-diisopropylaniline gave the corresponding arylimido complexes in clean reactions. Reaction of the titanium imido complex [Cp*Ti(N(Xyl)N)(N(t)Bu)(NH(2)(t)Bu)] with terminal arylacetylenes, such as phenylacetylene and tolylacetylene, led to C-H activation and the formation of alkynyl/amido complexes, whereas the arylimido complexes and cleanly underwent {2 + 2} cycloaddition, giving the azatitanacyclobutene derivatives. A single-crystal X-ray structure analysis of the azatitanacyclobutene [Cp*Ti(N(Xyl)N){kappa(2)N(2,6-C(6)H(3)Me(2))CTol[double bond, length as m-dash]CH}] () provided the first crystallographically characterized Markovnikov cycloaddition product of an imidotitanium complex with a terminal alkyne. The mechanistic aspects of the hydromanination of alkynes with the new Ti half sandwich complexes were studied and established a reversible {2 + 2} cycloaddition step and the cleavage of the metallacyclic intermediate as the rate determining step in the catalytic cycle. The titanium half sandwich imido complexes were found to be active catalysts for the inter- and intramolecular hydroamination of a broad range of alkynes and omega-aminoalkynes.

The catalytic hydroamination of alkynes

Catalytic additions of ammonia or primary and secondary amines to non-activated alkenes and alkynes are called hydroaminations. These reactions of fundamental simplicity represent the most atom efficient processes for the formation of amines, enamines and imines, which are important bulk and fine chemicals or building blocks in organic synthesis. Consequently, the development of corresponding hydroamination reactions has received much attention and great progress has been achieved in the case of catalytic hydroaminations of alkynes over the past four years. To illustrate this progress, this tutorial review will mostly focus on recent developments in the field of intermolecular hydroamination of alkynes that appeared in the literature between the end of 2002 and October 31, 2006.