Novel Ozone-Mediated Cleavage of the Benzhydryl Protecting Group from Aziridinyl Esters
摘要:
N-Benzhydryl aziridines-2-carboxylates can be readily obtained from the catalytic asymmetric aziridination reaction from N-benzhydrylimines and ethyl diazoacetate. Cleavage of the benzhydryl group by hydrogenolysis leads to ring opening when R = aryl. Surprisingly, ozone will selectively oxidize the benhydryl group in these aziridines even when R is an aryl group. This allows for a new deprotection strategy for these aziridines whose generality is explored.
Catalytic Asymmetric Aziridination with Borate Catalysts Derived from VANOL and VAPOL Ligands: Scope and Mechanistic Studies
作者:Yu Zhang、Aman Desai、Zhenjie Lu、Gang Hu、Zhensheng Ding、William D. Wulff
DOI:10.1002/chem.200701558
日期:2008.4.18
An extended study of the scope and mechanism of the catalyticasymmetricaziridination of imines with ethyl diazoacetate mediated by catalysts preparedfrom the VANOL and VAPOL ligands and triphenylborate is described. Nonlinear studies with scalemic VANOL and VAPOL reveal an essentially linear relationship between the optical purity of the ligand and the product suggesting that the catalyst incorporates
The iso-VAPOL ligand: synthesis, solid-state structure and its evaluation as a BOROX catalyst
作者:Anil K. Gupta、Xin Zhang、Richard J. Staples、William D. Wulff
DOI:10.1039/c4cy00742e
日期:——
and it is found that all three ligands have the cisoid conformations in the solid-state; the dihedral angle between the two aryl groups is less than 90°. In addition, all three ligands pack in the solid-state with no inter-molecular hydrogen bonds. This is the opposite to what has been reported for BINOL where all known structures exist with transoid conformations where the dihedral angle is >90° and
新的拱形联芳基配体iso-VAPOL是VAPOL的异构体,但具有VANOL的手性口袋。iso-VAPOL的合成涉及类似于VAPOL的环加成/电环化级联(CAEC),不同之处在于iso-VAPOL的起始原料成本不到其十分之一。确定了iso-VAPOL的固态结构以及VANOL的固态结构,因为以前没有报道过。将iso-VAPOL和VANOL的结构与VAPOL的已知固态结构进行了比较,发现所有三个配体在固态中均具有顺式构象。两个芳基之间的二面角小于90°。另外,所有三个配体都以固态堆积,没有分子间氢键。这与关于BINOL的报道相反,在BINOL中,所有已知的结构都存在具有反式构象的二面角> 90°,并且BINOL单元在相邻BINOL单元之间带有氢键。光谱证据包括给出的1 H和11 B NMR光谱表明,异VAPOL配体将以与B(OPh) 3形成BOROX催化剂的方式与以前通过光谱法和X射线晶体学报道
Facile Synthesis of Aziridines from Imines and Diazoesters or Aldehydes, Amines, and Diazoesters Using a Catalytic Amount of Lanthanide Triflate
作者:Satoshi Nagayama、Shu Kobayashi
DOI:10.1246/cl.1998.685
日期:1998.7
In the presence of a catalytic amount of lanthanide triflate (Ln(OTf)3), imines reacted with ethyl diazoester in hexane at room temperature to afford the corresponding aziridines in high yields with high diastereoselectivities. Based on these reactions, three-component reactions of various types of aldehydes, an amine, and ethyl diazoester have been developed to provide a general efficient route to
asymmetric aziridination. Aziridine yields were overall moderate to low (up to 33% isolated yield of the cis isomer) because of the competitive formation of diethyl maleate (7). The scope of the catalyst was studied with p- and m-substituted imines. NMR spectroscopic studies with 13C- and 15N-labeled EDA indicate that aziridine 6a is formed by carbenetransferfrom an EDA complex, [RuCl(EDA)(PNNP)]PF6
Novel Ozone-Mediated Cleavage of the Benzhydryl Protecting Group from Aziridinyl Esters
作者:Aniruddha P. Patwardhan、Zhenjie Lu、V. Reddy Pulgam、William D. Wulff
DOI:10.1021/ol050597t
日期:2005.5.1
N-Benzhydryl aziridines-2-carboxylates can be readily obtained from the catalytic asymmetric aziridination reaction from N-benzhydrylimines and ethyl diazoacetate. Cleavage of the benzhydryl group by hydrogenolysis leads to ring opening when R = aryl. Surprisingly, ozone will selectively oxidize the benhydryl group in these aziridines even when R is an aryl group. This allows for a new deprotection strategy for these aziridines whose generality is explored.