efficient synthetic route to unsymmetrically substituted dihydropyridine scaffolds via dehydrative [4 + 2] cycloaddition of N-tosylated α,β-unsaturated imines with aldehydes has been developed. This transformation is enabled by (i) the remarkable catalytic ability of the cationic Ru(IV) porphyrin complex to activate both the imino and carbonyl groups and (ii) the hydrophobic nature of the porphyrin ligand,
development of an efficient and mild strategy for C(sp3)–H bond activation of nitrogen-containing compounds without the utilization of any oxidant and metal is still highly desired and challenging. Herein, we present a metal-free reaction system that enables C–H bond functionalization of aliphatic sulfonamides using DABCO as a promoter under mild conditions, affording a series of α,β-unsaturated imines
Design of Planar Chiral Phosphoric Acids with a [2.2]Paracyclophanyl Backbone as Organocatalysts for the Highly Enantioselective Aza-Friedel–Crafts Reaction
作者:En Xie、Shaoying Huang、Xufeng Lin
DOI:10.1021/acs.orglett.9b01127
日期:2019.5.17
A new type of robust planarchiral phosphoric acid bearing a [2.2]paracyclophane scaffold was synthesized and shown to be an optimal catalyst in asymmetric aza-Friedel–Crafts reactions for the first synthesis of enantioenriched styryl indolylmethanamine derivatives in good yields with excellent enantioselectivities (93–>99% ee) under 0.5–1 mol % catalyst loading.
A General Aminocatalytic Method for the Synthesis of Aldimines
作者:Sara Morales、Fernando G. Guijarro、José Luis García Ruano、M. Belén Cid
DOI:10.1021/ja4111418
日期:2014.1.22
A general and efficient biomimetic method for the synthesis of aldimines from aldehydes and compounds bearing the NH2 group in the presence of pyrrolidine as a catalyst has been developed. These organocatalytic reactions, based on the application of the concept of nucleophilic catalysis, proceed with outstanding yields in the absence of acids and metals under simple conditions and minimum experimental manipulation. The method has been mainly applied to the synthesis of N-sulfinyl and N-sulfonyl imines, but its general validity has been proven with the preparation of representative N-phosphinoyl, N-alkyl, and N-aryl imines. These unprecedented reactions, which presumably occur via iminium activation without requiring acidic conditions, are an interesting and competitive alternative to the classical methods for preparing aldimines.
Highly enantioselective [4 + 2] cyclization of chloroaldehydes and 1-azadienes catalyzed by N-heterocyclic carbenes
作者:Teng-Yue Jian、Li-Hui Sun、Song Ye
DOI:10.1039/c2cc35273g
日期:——
Highly functionalized dihydropyridinones were synthesized via the N-heterocyclic carbene-catalyzed enantioselective [4 + 2] annulation of alpha-chloroaldehydes and azadienes. Hydrogenation of the resulted dihydropyridinones afforded the corresponding piperidinones with high enantiopurity.