Stereoselective Rh<sub>2</sub>(<i>S</i>-IBAZ)<sub>4</sub>-Catalyzed Cyclopropanation of Alkenes, Alkynes, and Allenes: Asymmetric Synthesis of Diacceptor Cyclopropylphosphonates and Alkylidenecyclopropanes
作者:Vincent N. G. Lindsay、Dominic Fiset、Philipp J. Gritsch、Soula Azzi、André B. Charette
DOI:10.1021/ja3099728
日期:2013.1.30
A mild and highly stereoselective rhodium(II)-catalyzed cyclopropanation of alkenes, alkynes, and allenes with diacceptor diazo compounds is reported. Using the phosphonate moiety as an efficient trans-directing group, the first catalytic asymmetric route to diacceptor cycloprop(en)ylphosphonates was developed by employing an α-cyano diazophosphonate and Rh(2)(S-IBAZ)(4) as chiral catalyst. The isosteric
报道了一种温和且高度立体选择性的铑 (II) 催化的烯烃、炔烃和丙二烯与二受体重氮化合物的环丙烷化反应。使用膦酸酯部分作为有效的反式导向基团,通过使用 α-氰基重氮膦酸酯和 Rh(2)(S-IBAZ)(4) 作为手性催化剂,开发了第一个催化不对称二受体环丙(烯)基膦酸酯的路线。膦酸和羧酸衍生物的等排特性允许在该过程中替代使用 α-氰基重氮酯,从而以高产率和立体选择性生成 α-氰基环丙(烯)基羧酸酯。利用该系统中涉及的氰基卡宾中间体的特殊反应性,相容底物的范围可以扩展到取代的丙二烯,
Dirhodium(II) Tetrakis[methyl 2-oxaazetidine-4-carboxylate]: A Chiral Dirhodium(II) Carboxamidate of Exceptional Reactivity and Selectivity
作者:Michael P. Doyle、Simon B. Davies、Wenhao Hu
DOI:10.1021/ol005730q
日期:2000.4.1
[formula: see text] A new chiral azetidinone-carboxylate ligand for dirhodium(II) catalysis enhances reactivity toward diazodecomposition and selectivity toward cyclopropanation enabling diazomalonates, vinyldiazoacetates, and aryldiazoacetates to be effectively used with a dirhodium(II) carboxamidate catalyst.
Cyclization of L-aspartic acid to (S)-4-benzyloxycarbonyl-2-azetidinone followed by transesterification of this compound in the presence of titanium (IV) tetrabutoxide proved to be an exceedingly efficient method of general application for the preparation of (S)-4-alkoxycarbonyl-beta-lactams.
Controlled Polymerization of β-Lactams Using Metal−Amido Complexes: Synthesis of Block Copoly(β-peptides)