Organocatalytic and enantioselective [4+2] cyclization between hydroxymaleimides and: Ortho -hydroxyphenyl para -quinone methide-selective preparation of chiral hemiketals
A cinchona alkaloid squaramide promoted enantioselective [4+2] cyclization between hydroxymaleimides and ortho-hydroxyphenyl p-QMs has been disclosed, and a wide range of chiral hemiketals containing chromane and succinimide frameworks with two adjacent quaternary stereogenic centers have been prepared for the first time with excellent results (up to 99% yield, up to 99?:?1 dr, up to >99% ee) under mild conditions. This journal is
Palladium(II)-Catalyzed Oxidative Homo- and Cross-Coupling of Aryl ortho -sp2 C-H Bonds of Anilides at Room Temperature
The preparation of secondary 2,2'-bisanilides has been successfully achieved through an oxidative coupling of aryl ortho-sp2 C-H bonds of anilides in the presence of catalytic Pd(OAc)2 and K2S2O8 as an oxidant in MsOH/CF3CO2H (TFA) at room temperature (25 °C). The aromatic rings of anilides substituted by various electron-donating or electron-withdrawing groups are tolerant in these coupling reactions.
Mei, Chong,Lu, Wenjun
p. 4812 - 4823
(2018/04/26)
Organocatalytic Asymmetric Annulation between Hydroxymaleimides and Nitrosoarenes: Stereoselective Preparation of Chiral Quaternary N-Hydroxyindolines
An unusual and highly effective asymmetric annulation of nitrosoarenes with hydroxymaleimides catalyzed by a chiral bifunctional amine squaramide catalyst has been disclosed. A wide range of highly fused chiral N-hydroxyindolines with two consecutive quaternary stereocenters and multifunctional groups were directly and effectively prepared in excellent yields (up to >99%) with complete regioselective cyclization and excellent stereoselectivities (up to >99:1 dr and >99% ee). The efficiency and potentials of the new reaction and the target chiral entities were well demonstrated by delicate transformations into a series of new chiral indolines.
Reductive amidation of nitroarenes: a practical approach for the amidation of natural products
A simple and practical approach for the one-pot conversion of nitroarenes into amide derivatives has been developed. Zinc and acetic acid are utilized as a reducing agent, and acyl chloride and triethylamine are used as the acylating agent in DMF with good yield (~60%) of the amide. This method was applicable to manzamine A (1), where the yield of 6-cyclohexamidemanzamine A (7) was significantly improved (56%) by this approach relative to (17%) by beginning with the amine.
Wahba, Amir E.,Peng, Jiangnan,Hamann, Mark T.
supporting information; experimental part
p. 3901 - 3904
(2009/10/04)
Bis(salicylaldehyde)ethylenedi-iminecobalt(II)-catalysed Oxidation of Aromatic Amins with Oxygen
N-n-Butylanilines undergo N-dealkylation to give a primary amine and butyrylaldehyde by oxidation with oxygen in the presence of bis(salicylaldehyde)ethylenedi-iminecobalt(II) (CoIIsalen) as a catalyst.High conversions are obtained with high catalyst concentrations and low / ratios (r).Inspection of the effect of catalyst and substrate concentrations on initial reaction rates (Vin) shows poor sensitivity to the electronic effect of the nuclear substituent.Some anilines give azo derivatives at a lower rate in the same conditions.