Protoberberines from Reissert-Compounds VIII [1]. Oxazoloisoquinolines, New and Efficient Educts for the Synthesis of 8-Oxoprotoberberines
作者:Eberhard Reimann、Fritz Grasberger、Kurt Polborn
DOI:10.1007/s00706-003-0013-5
日期:2003.6
Certain benzylated oxazoloisoquinolinones readily available fromReissert compounds provided an efficient access to 8-oxoprotoberberines in three steps. A series of these new precursors as well as several oxoprotoberberines were prepared and the scope and limitation of this procedure were investigated.
Asymmetric hydrogenation: The title reaction provides an efficient and rapid access to chiral 1‐ and 3‐substituted 1,2,3,4‐tetrahydroisoquinolines with excellent enantioselectivity (see scheme; L=ligand). A preliminary mechanistic study indicates that the 1,2‐hydride addition might be the initial step in the reaction. The method has been used in the synthesis of urinary antispasmodic drug (+)‐solifenacin
不对称氢化:标题反应可高效且快速地获得手性1和3-取代的1,2,3,4-四氢异喹啉,且具有出色的对映选择性(参见方案; L =配体)。初步的机理研究表明,添加1,2-氢化物可能是反应的第一步。该方法已用于尿解痉药(+)-索非那新的合成。
Synthesis of Chiral Piperazines via Hydrogenation of Pyrazines Activated by Alkyl Halides
A facile method has been developed for the synthesis of chiral piperazines through Ir-catalyzed hydrogenation of pyrazines activated by alkyl halides, giving a wide range of chiral piperazines including 3-substituted as well as 2,3- and 3,5-disubstituted ones with up to 96% ee. The high enantioselectivity, easy scalability, and concise drug synthesis demonstrate the practical utility.
Highly efficient iridium‐catalyzed asymmetrichydrogenations of simple 2‐substituted pyridinium salts gives the chiral 2‐substituted piperidines with up to 93 % ee (see picture; cod=1,5‐cyclooctadiene; synphos=(5,6),(5′,6′)‐bis(ethylenedioxy)‐2,2′‐bis(diphenylphosphino)‐1,1′‐biphenyl). The key feature of this strategy is the activation of simple pyridines as the pyridinium salts, thus eliminating substrate