Phosphine-catalyzed [5+1] annulation of β′-acetoxy allenoates: straightforward access to tetrahydroquinoline derivatives

Abstract

An unprecedented phosphine-catalyzed [5+1] annulation of β’-acetoxy allenoates with 1,5-dinucleophiles has been developed, which provides novel and facile accesses to functionalized tetrahydroquinolines in good to high yields in the presences...

A highly diastereoselective (5+1) annulation of allenoates and pyrazolones catalyzed by CH3OK

“…Nucleophilic phosphine-catalyzed annulation reaction has proven to be one of the most practical and powerful methods to construct structurally diverse and complex molecules. 9–12 In contrast, there has been no Brønsted base-catalyzed annulation of allenoates. Our ongoing interest in phosphine-allenoate reactions 13 led us to design a new kind of allenoate II with an electrophilic allyl group installed in the α position of the common allenoate I (Scheme 1a).…”

Concise synthesis of pyrrolo[3,4-c]quinolines via a P(NMe2)3-catalyzed [4 + 2] annulation followed by a Zn/AcOH-mediated reduction–hydroamination–isomerization

“…10 Therefore, it is very meaningful and necessary to develop the application of 2-amino-β-nitrostyrenes. On the other hand, β′-acetoxy allenoates, 11 acting as C1–C4 synthons, have been popularly employed in the field of tertiary phosphine or amine catalysis since the pioneering work reported by Tong's group. 11 a Herein, we report the synthesis of pyrrolo[3,4- c ]quinolines via a phosphine-catalyzed [4 + 2] annulation followed by a zinc/acetic acid-mediated reduction–cyclization–isomerization cascade process of 2-amino-β-nitrostyrenes and β′-acetoxy allenoates.…”

“…As shown in Scheme 6, a plausible reaction mechanism for this tandem reaction was proposed considering the commonly accepted mechanism of phosphine-catalyzed reactions of electron-deficient alkenes with β′-acetoxy allenoates. 11 The reaction started with a nucleophilic addition between phosphine catalyst PR 3 and β′-acetoxy allenoate 2 to generate intermediate B , which was transformed into intermediate C through an elimination reaction. Intermediate C was converted to key eneyne D in the presence of base and regenerated the phosphine catalyst PR 3 .…”