A highlyenantioselective [2+2] cycloaddition reaction of alkylidene malonates with the internal CC bond of N-allenamides was developed with a MgII/N,N′-dioxide complex as a catalyst. Various polysubstituted methylenecyclobutanes were afforded in good yields (up to 99%) and excellent enantioselectivities (up to 96% ee) under mild conditions. The utility of the donor–acceptor cyclobutane product was
以Mg II / N,N'-二氧化物配合物为催化剂,开发了亚烷基丙二酸酯与N-亚酰胺的内部C C键的高对映选择性[2 +2]环加成反应。在温和的条件下,可以提供多种多取代的亚甲基环丁烷,收率好(高达99%)和出色的对映选择性(高达96%ee)。在甲硅烷基烯醇醚的正式[4 + 2]环合反应中,供体-受体环丁烷产品的用途已证明可作为掩蔽的1,4-偶极子。
Catalytic asymmetric multicomponent reactions of isocyanide, isothiocyanate and alkylidene malonates
Several unique chiral 3,4-dihydro-2H-pyrrole-2-thiones were made readily available by carrying out, in each case, a chiral-Mg(OTf)2/N,N′-dioxide-complex-promoted formal [2+1+2] cycloaddition in the presence of tetraethylenediamine. Control experiments revealed that in situ-generated ammonium thiocyanate was crucial for maintaining high enantioselectivity through its inhibition of the HNCS-induced racemization
几种独特的手性 3,4-二氢-2 H-吡咯-2-硫酮可通过在每种情况下进行手性-Mg(OTf) 2 / N , N '-二氧化物-复合物促进的缩合[ 2+1+2] 在四亚乙基二胺存在下的环加成。对照实验表明,原位生成的硫氰酸铵对于通过抑制 HNCS 诱导的产物外消旋化来保持高对映选择性至关重要。
Highly Stereoselective Intermolecular Oxy-Michael Addition Reaction to α,β-Unsaturated Malonate Esters
作者:David J. Buchanan、Darren J. Dixon、Felix A. Hernandez-Juan
DOI:10.1021/ol049820x
日期:2004.4.1
The highly diastereoselective oxy-Michael addition of the "naked" anion of (6S)-methyl delta lactol to alkylidiene-, arylidene-, and heteroarylidenemalonate derivatives leading to the direct formation of THP*-protected beta-hydroxy ester derivatives is described. Subsequent acid-mediated deprotection affords the enantioenriched aldol products in quantitative yields.