1247949-41-2Relevant academic research and scientific papers
Catalytic asymmetric hydrogenation of 3-substituted benzisoxazoles
Ikeda, Ryuhei,Kuwano, Ryoichi
scheme or table, p. 6901 - 6915 (2012/09/07)
A variety of 3-substituted benzisoxazoles were reduced with hydrogen using the chiral ruthenium catalyst, {RuCl(p-cymene)[(R,R)-(S,S)-PhTRAP]}Cl. The ruthenium-catalyzed hydrogenation proceeded in high yield in the presence of an acylating agent, affording α-substituted o-hydroxybenzylamines with up to 57% ee. In the catalytic transformation, the N-O bond of the benzisoxazole substrate is reductively cleaved by the ruthenium complex under the hydrogenation conditions. The C-N double bond of the resulting imine is saturated stereoselectively through the PhTRAP-ruthenium catalysis. The hydrogenation produces chiral primary amines, which may work as catalytic poisons, however, the amino group of the hydrogenation product is rapidly acylated when the reaction is conducted in the presence of an appropriate acylating agent, such as Boc2O or Cbz-OSu.
A divergent and selective synthesis of isomeric benzoxazoles from a single N-Cl imine
Chen, Cheng-Yi,Andreani, Teresa,Li, Hongmei
supporting information; experimental part, p. 6300 - 6303 (2012/01/05)
A divergent and regioselective synthesis of either 3-substituted benzisoxazoles or 2-substituted benzoxazoles from readily accessible ortho-hydroxyaryl N-H ketimines is described. The reaction proceeds in two distinct pathways through a common N-Cl imine intermediate: (a) N-O bond formation to form benzisoxazole under anhydrous conditions and (b) NaOCl mediated Beckmann-type rearrangement to form benzoxazole, respectively. The reaction path also depends on the electronic nature of the aromatic ring, with the electron-rich aromatic rings favoring the rearrangement and the electron-deficient rings favoring the N-O bond formation. A Beckmann-type rearrangement mechanism via net [1,2]-aryl migration for the formation of 2-substituted benzoxazole is proposed.
Chiral phosphoric acid-catalyzed enantioselective transfer hydrogenation of ortho-hydroxyaryl alkyl N - H ketimines
Nguyen, Thanh Binh,Bousserouel, Hadjira,Wang, Qian,Gueritte, Francoise
supporting information; experimental part, p. 4705 - 4707 (2010/12/24)
The first enantioselective chiral phosphoric acid-catalyzed transfer hydrogenation of unprotected ortho-hydroxyaryl alkyl N - H ketimines using Hantszch di-tert-butyl ester as a reductant is reported. A variety of ortho-hydroxybenzylamines were obtained in good to excellent yields and enantiomeric excesses.
