Merging Gold Catalysis and Brønsted Acid Catalysis for the Synthesis of Tetrahydrobenzo[b][1,8]naphthyridines

Abstract

A gold(I)/Brønsted acid-catalyzed cyclization of 2-azidobenzaldehydes with 3-aza-1,6enynes has been developed for the synthesis of tetrahydrobenzo[b] [1,8]naphthyridine derivatives. This protocol enabled the modular synthesis of tetracyclic heterocycles in one operation with water and nitrogen gas as the byproducts.

An efficient 3-acylquinoline synthesis from acetophenones and anthranilviaC(sp3)–H bond activation mediated by Selectfluor

“…[12][13][14] The synthesis of quinolines has been an active area for many years and as a result, a number of efficient synthetic methods have been developed, [15][16][17][18][19][20] such as the classical Skraup, [21][22][23] Combes, [24][25][26] Friedlander, [27][28][29] Gould-Jacobs, [30][31][32] and Doebner-von Miller reactions. [33][34][35][36] More recently, alternative strategies for the quinoline synthesis such as domino cycloadditions [37][38][39][40][41] and transition-metal mediated methods [42][43][44][45] have been introduced. However, most of the existing methods necessitate the use of strong acid or base conditions, high reaction temperatures, the use of expensive/toxic metal catalysts and frequently require the use of expensive, highly functionalized starting materials.…”

Synthesis of spiropyrrolidine oxindoles through Rh(II)-catalyzed olefination/cyclization of diazooxindoles and vinyl azides

“…Vinyl azides serve as two-atom partners in the reported Rh-catalyzed cyclopropanation [27] (Scheme 2a) and Cu-catalyzed [3+2] cycloaddition [28] (Scheme 2b) reactions. Following our previous studies on the azide chemistry [29][30][31] and cycloaddition reactions [32,33], we directed our attention towards developing new cycloaddition reactions of vinyl azides and diazo compounds, in which vinyl azides may serve as three-atom synthons. Herein, we report a Rh(II)-catalyzed [3+1+1] annulation of vinyl azides and 3-diazooxindoles, enabling the facile synthesis of spiropyrrolidine oxindoles (Scheme 2d).…”

Azofuran activation for annulative rearrangement enabled by gold(i)/Brønsted acid relay catalysis

“…2 In particular, gold/Brønsted acid synergistic catalysis has been increasingly developed, because such catalysis could remarkably enhance the efficiency and selectivity of chemical transformations compared with gold or Brønsted acid alone. 3 However, the application of gold/Brønsted acid dual catalysis remains very limited and immature. Consequently, developing new gold/Brønsted acid dual catalysis not only benefits the arsenal of synthetic methodologies for constructing significant molecules, but also expands the chemical space of drug discovery and other fields.…”

“…With 3-yne-1,2-diol 1a and diazonium tetrafluoroborate 2a as representative examples, this might initially involve Au( i )-catalyzed cyclodehydration, and subsequent proto-deauration yields furan intermediate 7 , together with the regeneration of gold catalyst for the next catalytic cycle. 3 Of the stoichiometric amounts of HBF 4 generated in the reaction process, half are neutralized by NaHCO 3 , part are consumed to form salts with the newly formed N -arylamino products, and the rest act as Brønsted catalysts for azofuran activation. Along this line, the protonation of azofuran 4 occurs to yield intermediate D , followed by 1,6-nucleophilic addition of furan 7 , accessing bifuran intermediate E .…”