200490-92-2Relevant academic research and scientific papers
Sequential reductive amination-hydrogenolysis: A one-pot synthesis of challenging chiral primary amines
Nugent, Thomas C.,Negru, Daniela E.,El-Shazly, Mohamed,Hu, Dan,Sadiq, Abdul,Bibi, Ahtaram,Umar, M. Naveed
supporting information; experimental part, p. 2085 - 2092 (2011/10/19)
Difficult-to-access chiral primary amines were formed in good to high yield and ee using a rare example of a one-pot synthesis from prochiral ketones (sequential reductive amination-hydrogenloysis). As a highlight we also demonstrate a one-pot reductive amination-hydrogenolysis-reductive amination (five reactions) of ortho-methoxyacetophenone resulting in the chiral diamine 1-(2-methoxyphenyl)ethyl-(2-pyridylmethyl)-amine (4) (58% overall yield, >99% ee), a new organocatalyst for aqueous enantioselective aldol reactions. Copyright
A general study of aryloxo and alkoxo ligands in the titanium-catalyzed intermolecular hydroamination of terminal alkynes
Tillack, Annegret,Khedkar, Vivek,Jiao, Haijun,Beller, Matthias
, p. 5001 - 5012 (2007/10/03)
A general study of the regioselective hydroamination of terminal alkynes in the presence of Ti(NEt2)4 and different aryloxo and alkoxo ligands is presented. Depending on the ligand the regioselectivity towards the Markovnikov and the anti-Markovnikov addition product can be controlled. The experimentally observed isomer distribution is explained perfectly by detailed theoretical investigations which demonstrate that the regioselectivity is determined by the relative stability of the corresponding alkynetitanium π complexes. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
A general study of [(η5-Cp′)2Ti(η 2-Me3SiC2SiMe3)]-catalyzed hydroamination of terminal alkynes: Regioselective formation of Markovnikov and anti-Markovnikov products and mechanistic explanation (Cp′=C (5)H(5), C(5)H(4)Et, C(5)Me(5))
Tillack, Annegret,Jiao, Haijun,Castro, Ivette Garcia,Hartung, Christian G.,Beller, Matthias
, p. 2409 - 2420 (2007/10/03)
A general study of the regioselective hydroamination of terminal alkynes in the presence of [(η5-Cp)2Ti(η2-Me 3SiC2SiMe3)] (1), [(η5-CpEt) 2Ti(η2-Me3SiC2SiMe3)] (CpEt= ethylcyclopentadienyl) (2), and [(η5-Cp*) 2Ti(η2-Me3SiC2SiMe3)] (Cp=pentamethylcyclopentadienyl) (3) is presented. While aliphatic amines give mainly the anti-Markovnikov products, anilines and aryl hydrazines yield the Markovnikov isomer as main products. Interestingly, using aliphatic amines such as n-butylamine and benzylamine the different catalysts lead to a significant change in the observed regioselectivity. Here, for the first time a highly selective switch from the Markovnikov to the anti-Markovnikov product is observed simply by changing the catalyst. Detailed theoretical calculations for the reaction of propyne with different substituted anilines and tert-butylamine in the presence of [(η5-C5H5)Ti(= NR)(NHR)] (R=4-C6H4X; X=H, F, Cl, CH3, 2,6-dimethylphenyl) reveal that the experimentally observed regioselectivity is determined by the relative stability of the corresponding π-complexes 10. While electrostatic stabilization favors the Markovnikov performance for aniline, the steric repulsive destabilization disfavors the Markovnikov performance for tert-butylamine.
Controlling selectivity: From Markovnikov to anti-Markovnikov hydroamination of alkynes
Tillack, Annegret,Khedkar, Vivek,Beller, Matthias
, p. 8875 - 8878 (2007/10/03)
A remarkable control of regioselectivity is achieved for the titanium-catalyzed intermolecular hydroamination of various alkynes. Proper choice of the ligand enables a selectivity switch from the Markovnikov to the anti-Markovnikov products from M:anti-M = > 90:10 to >10:90. Depending on the catalyst a remarkable control of regioselectivity is achieved for the titanium-catalyzed intermolecular hydroamination of various alkynes. Proper choice of sterically hindered phenol ligands such as 1 and 4 enables a selectivity switch from the Markovnikov to the anti-Markovnikov products from M:anti-M = > 90:10 to > 10:90.
A Dramatic Effect of Aryloxo Ligands on the Titanium-Catalyzed Hydroamination of Alkynes
Khedkar, Vivek,Tillack, Annegret,Beller, Matthias
, p. 4767 - 4770 (2007/10/03)
(Equation Presented) The aryloxotitanium complex 1 is a highly chemo- and regioselective catalyst for intermolecular hydroamination of terminal alkynes. Branched imines are obtained in good to excellent yield (up to 99%) with various primary aromatic and aliphatic amines.
A mild, convenient, and inexpensive method for converting imines into amines: Tin-catalyzed reduction with polymethylhydrosiloxane (PMHS)
Lopez, Rosa M.,Fu, Gregory C.
, p. 16349 - 16354 (2007/10/03)
We have developed a mild, convenient, and inexpensive protocol for reducing imines to amines. Thus, treatment of any of a wide array of imines with catalytic n-butyltris(2-ethylhexanoate)tin and stoichioimetric polymethylhydrosiloxane (PMHS) in ethanol at room temperature cleanly affords the desired secondary amine product. Alkyl bromides, alkynes, epoxides, esters, nitriles, and olefins are inert toward these reduction conditions, whereas aldehydes, ketones, and nitro compounds are not.
