Highly Enantioselective Synthesis of 1,3-Oxazolidin-2-imine Derivatives by Asymmetric Cycloaddition Reactions of Vinyloxiranes with Unsymmetrical Carbodiimides Catalyzed by Palladium(0) Complexes
摘要:
4-Vinyl-1,3-oxazoilidin-2-imine derivatives have been synthesized by cycloaddition reactions of 2-vinyloxiranes with unsymmetrical carbodiimides catalyzed by palladium(0) complexes-in excellent total isolated yields. After reaction two compounds were always formed, one of which was isolated as the major product. A bulky alkyl group on one of the nitrogen atoms of the carbodiimide enhanced the product ratio in favor of the N-aryl-3-alkyl-1,3-oxazolidin-2-imine. Highly enantioselective cycloadducts (up to >99% ee) were formed by using TolBINAP as the chiral phosphine ligand, in THF at ambient temperatures. The enantiodetermination is believed to be dependent on nucleophilic attack of the anionic nitrogen of the carbodiimide due to the steric interaction of the carbodiimide substituents with the chiral phosphine ligand.
A New Synthetic Protocol for the Preparation of Carbodiimides Using a Hypervalent Iodine(III) Reagent
作者:Yunyang Wei、Chenjie Zhu、Dan Xu
DOI:10.1055/s-0030-1258414
日期:2011.3
A new, simple, and efficient preparation of symmetrical and unsymmetrical carbodiimides from the corresponding thioureas via dehydrosulfurization using a hypervalent iodine(III) reagent is described. The oxidation afforded carbodiimides in excellent yields and high selectivity. A possible mechanism for the transformation is proposed. desulfurization - hypervalent iodine - oxidations - carbodiimides
An efficient [3+2] cycloaddition of nitrones and carbodiimides has been developed. This 1,3-dipolar cycloaddition features high regioselectivity, mild and metal-free conditions, excellent functional group compatibility, and a broad substrate scope. The X-ray structures of two regio-isomers confirmed the regioselectivity of this transformation.
A facile method for the preparation of carbodiimides from thioureas and (Boc) 2 O
作者:He Wu、Yan-Fang Sun、Chen Zhang、Chun-Bao Miao、Hai-Tao Yang
DOI:10.1016/j.tetlet.2018.01.025
日期:2018.2
A concise method for the preparation of carbodiimides from thioureas using di-tert-butyl dicarbonate [(Boc)2O] as the dehydrosulfurizative reagent has been developed. Using DMAP as the catalyst, a variety of symmetric and asymmetric 1,3-diaryl thioureas were converted into the corresponding carbodiimides efficiently in a short time.
Cascade Nucleophilic Attack/Addition Cyclization Reactions to Synthesize Oxazolidin-2-imines via (<i>Z</i>)-2-Bromo-3-phenylprop-2-en-1-ols/3-phenylprop-2-yn-1-ols and Diphenyl Carbodiimides
Two concise strategies to synthesize oxazolidin-2-imines by cascade nucleophilic attack/addition cyclization reactions of (Z)-2-bromo-3-phenylprop-2-en-1-ols/3-phenylprop-2-yn-1-ols and diphenyl carbodiimides without a transition-metal catalyst have been developed. The reactions exhibited good substrate applicability tolerance, and a variety of substituted (Z)-4-((Z)-benzylidene)-N,3-diphenyloxazolidin-2-imines
( Z )-2-bromo-3-phenylprop-2-en-1-ols/3-phenylprop-2-yn-1-ols的级联亲核攻击/加成环化反应合成恶唑烷-2-亚胺的两种简明策略已经开发了没有过渡金属催化剂的二苯基碳二亚胺。该反应表现出良好的底物适用性,以中等至优异的收率合成了多种取代的( Z )-4-(( Z )-亚苄基) -N ,3-二苯恶唑烷-2-亚胺,具有良好的立体选择性。该报告还提供了一种方便的策略来合成 3-phenylprop-2-yn-1-ols ( Z)-2-bromo-3-phenylprop-2-en-1-ols。经济实用的方法为恶唑烷-2-亚胺的潜在工业合成提供了很大的优势。