Chiral relay in NHC-mediated asymmetric β-lactam synthesis I; substituent effects in NHCs derived from (1R,2R)-cyclohexane-1,2-diamine
摘要:
The synthesis of a range of C-2-symmetric imidazolinium salts from (1R,2R)-cyclohexane-1,2-diamine, and an evaluation of the reactivity and asymmetric induction of the derived NHCs as catalysts for the asymmetric synthesis of beta-lactams, is reported. In this series, optimal enantioselectivity (up to 70% ee) is observed using N-benzyl or N-1-naphthylmethyl-substituted NHCs, consistent with a chiral relay effect operating to dictate the stereochemical outcome of this reaction. (C) 2010 Elsevier Ltd. All rights reserved.
Catalytic Enantioselective [3 + 2] Cycloaddition of α-Keto Ester Enolates and Nitrile Oxides
作者:Samuel L. Bartlett、Yoshihiro Sohtome、Daisuke Hashizume、Peter S. White、Miki Sawamura、Jeffrey S. Johnson、Mikiko Sodeoka
DOI:10.1021/jacs.7b03782
日期:2017.6.28
An enantioselective [3 + 2] cycloaddition reaction between nitrileoxides and transiently generated enolates of α-keto esters has been developed. The catalyst system was found to be compatible with in situ nitrile oxide-generation conditions. A versatile array of nitrileoxides and α-keto esters could participate in the cycloaddition, providing novel 5-hydroxy-2-isoxazolines in high chemical yield
In non-racemic (1R,2R)-(1,2-dialkyl)-1,2-diaminocyclohexane palladium dichloride complexes the C2 symmetry of the diamine ligand is broken, resulting in selective R,S-coordination.
A series of chiral and achiral cyclic seleno- and thiourea compounds bearing benzyl groups on N-atoms were prepared from enetetramines and appropriate Group VI elements in good yields. All the synthesized compounds were characterized by elemental analysis, FT-IR, 1H NMR and 13C NMR spectroscopy, and the molecular and crystal structures of (R,R)-4b and (R,R)-5b were confirmed by the single-crystal X-ray
一系列手性和非手性环状硒和硫脲化合物在N原子上带有苄基,由烯四胺和适当的 VI 族元素以良好的收率制备。所有合成的化合物均通过元素分析、FT-IR、1 H NMR和13 C NMR光谱以及(R,R) - 4b和(R,R) - 5b的分子和晶体结构进行了表征经单晶X射线衍射法证实。这些测定了它们对代谢酶乙酰胆碱酯酶、丁酰胆碱酯酶和α-糖苷酶的活性。这些手性和非手性烯四胺的硒脲和硫脲衍生物有效抑制 AChE 和 BChE,IC 50值分别在 3.32–11.36 和 1.47–9.73 µM 范围内。此外,这些化合物抑制 α-糖苷酶,IC 50值在 1.37 和 8.53 µM 之间变化。结果表明,与标准抑制剂相比,所有合成的化合物对上述酶均表现出优异的抑制活性。代表性地,对α-糖苷酶最有效的化合物,(S,S)-5b,比标准抑制剂阿卡波糖强 12 倍;图 7b和8a作为对胆碱酯酶最有效的化合物,分别比标准抑制剂他克林对乙酰胆碱酯酶
Ni-Catalyzed Dual C–H Annulation of Benzimidazoles with Alkynes for Synthesis of π-Extended Heteroarenes
作者:Shao-Long Qi、Yue Li、Jiang-Fei Li、Tao Zhang、Yu-Xin Luan、Mengchun Ye
DOI:10.1021/acs.orglett.1c01253
日期:2021.5.21
The synthesis, structure and properties of diazaphospholes: Reagents and ligands for asymmetric synthesis
作者:Antonette De la Cruz、Kevin J Koeller、Nigam P Rath、Christopher D Spilling、Isabel C.F Vasconcelos
DOI:10.1016/s0040-4020(98)00502-x
日期:1998.8
Reaction of C-2 diamines with PCl3 and Et3N in toluene, followed by water or hydrogen sulfide, gave a series of cyclic phosphorous acid diamides (diazaphosphole oxides) and thiophosphorous acid diamides (diazaphosphole sulfides), respectively. Similarly, reaction of diamines with phenyl dichlorophosphine gave phenyl diazaphospholes. The synthesis, properties, and structure of these diazaphospholes are reported. (C) 1998 Elsevier Science Ltd. All rights reserved.