1204705-03-2Relevant articles and documents
Self-supported chiral titanium cluster (SCTC) as a robust catalyst for the asymmetric cyanation of imines under batch and continuous flow at room temperature
Seayad, Abdul M.,Ramalingam, Balamurugan,Chai, Christina L. L.,Li, Chuanzhao,Garland, Marc V.,Yoshinaga, Kazuhiko
, p. 5693 - 5700 (2012/06/15)
A robust heterogeneous self-supported chiral titanium cluster (SCTC) catalyst and its application in the enantioselective imine-cyanation/Strecker reaction is described under batch and continuous processes. One of the major hurdles in the asymmetric Strecker reaction is the lack of availability of efficient and reusable heterogeneous catalysts that work at room temperature. We exploited the readily hydrolyzable nature of titanium alkoxide to synthesize a self-supported chiral titanium cluster (SCTC) catalyst by the controlled hydrolysis of a preformed chiral titanium-alkoxide complex. The isolated SCTC catalysts were remarkably stable and showed up to 98% enantioselectivity (ee) with complete conversion of the imine within 2 h for a wide variety of imines at room temperature. The heterogeneous catalysts were recyclable more than 10 times without any loss in activity or selectivity. The robustness, high performance, and recyclability of the catalyst enabled it to be used in a packed-bed reactor to carry out the cyanation under continuous flow. Up to 97% ee and quantitative conversion with a throughput of 45 mgh-1 were achieved under optimized flow conditions at room temperature in the case of benzhydryl imine. Furthermore, a three-component Strecker reaction was performed under continuous flow by using the corresponding aldehydes and amines instead of the preformed imines. A good product distribution was obtained for the formation of amino nitriles with ee values of up to 98%. Synthetically useful ee values were also obtained for challenging α-branched aliphatic aldehyde by using the three-component continuous Strecker reaction.
Highly enantioselective titanium-catalyzed cyanation of imines at room temperature
Seayad, Abdul Majeed,Ramalingam, Balamurugan,Yoshinaga, Kazuhiko,Nagata, Takushi,Chai, Christina L. L.
supporting information; experimental part, p. 264 - 267 (2010/03/24)
(Figure presented) A highly active and enantioselective titanium-catalyzed cyanatlon of imines at room temperature Is described. The catalyst used Is a partially hydrolyzed titanium alkoxide (PHTA) precatalyst together with a readily available N-salicyl-β-aminoalcohol ligand. Up to 98% ee was obtained with quantitative yields In 15 min of reaction time using 5 mol % of the catalyst. Various N-protecting groups such as benzyl, benzhydryl, Boc, and PMP are tolerated.
A remarkable titanium-catalyzed asymmetric strecker reaction using hydrogen cyanide at room temperature
Ramalingam, Balamurugan,Seayad, Abdul Majeed,Chuanzhao, Li,Garland, Marc,Yoshinaga, Kazuhiko,Wadamoto, Manabu,Nagata, Takushi,Chai, Christina L. L.
supporting information; experimental part, p. 2153 - 2158 (2010/11/04)
Close to perfect enantioselectivity (up to 98% ee) is obtained for the formation of amino nitrites using hydrogen cyanide (HCN) as the cyanide source at room temperature for the first time. In an operationally simple process, the catalyst generated from a partially hydrolyzed titanium alkoxide (PHTA) and (S)-N-salicyl-ss-amino alcohol ligand, catalyzes the cyanation of imines in a short reaction time.
TITANIUM COMPOUNDS AND PROCESS FOR CYANATION OF IMINES
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Page/Page column 40; 42, (2010/09/03)
The present invention relates to titanium catalysts for synthesis reactions produced by bringing a reaction mixture comprising a titanium alkoxide and a ligand in contact with water, wherein the ligand is represented by the general formula (e), wherein R1, R2, R3, and R4 are independently a hydrogen atom, an alkyl group, or the like, and (A) represents a group with two or more carbon atoms. The titanium catalysts may be isolated in solid form and may be stored. The invention further relates to a process for cyanation of imines, wherein the process comprises reacting an imine with a cyanating agent in the presence of the titanium catalyst.
