Recent Progress in the Reactions of Aurone-Derived Azadienes

Abstract

Owing to the important physiological and pharmacological activities of benzofuran compounds, the exploration for efficient synthesis methods is of great value and wide application. Aurone-derived azadienes have been identified to be effective reactants in the field of organic synthesis owing to the driving force of aromatization. A large number of reactions based on 1,4-conjugate addition and tandem cyclization have been reported, which exhibited great advantages in the construction of heterocycles with benzofuran skeletons. In this paper, the recent progress in the chemical transformations of aurone-derived azadienens is reviewed, with emphasis on the employed catalytic system and the plausible mechanism of some reactions.

Vinylene Carbonate as Synthon in Transition Metal‐Catalyzed C−H Bond Activation/Annulation Reactions

“…Previously, unstable hydroxyacetylene was often used for the synthesis of phenols or aldehydes through cyclization processes involving this C2 synthon [19,23,24] . Until 2009, the discovery of vinylene carbonate provided an alternative reagent: it is indeed more stable, cheaper and more selective than hydroxyacetylene.…”

Asymmetric reactions involving isobenzopyrylium ion intermediates

“…The asymmetric addition reactions of C-nucleophiles to isobenzopyrylium ions at the 1-position provided a straight route to structurally diverse chiral 1-substituted 1H-isochromene derivatives. [102][103][104] In 2016, the Enders group demonstrated the type of asymmetric addition could be realized under a combination of Ag2CO3 and chiral phosphoric acid, but only with moderate success (Scheme 10a). 105 Just Peng and his co-workers disclosed an efficient asymmetric addition of isobenzopyrylium with diazomethylphosphonate as Cnucleophile (Scheme 10b).…”

Enantioselective Synthesis of Spiroketals and Spiroaminals via Gold and Iridium Sequential Catalysis

“…Accordingly, multifaceted endeavors have been dedicated to develop efficient synthetic methodologies for the preparation of enantioenriched spiroketals [4, 5] . As a reliable and atom‐economic method, the cascade addition/spiroketalization reaction of exocyclic vinyl ethers or enamides with suitable amphiphilic reactants received considerable attentions (Scheme 1a) [6–8] . Due to their poor stability, the vinyl ether and enamide intermediates usually formed in situ by gold‐catalyzed cycloisomerization of alkynyl alcohols or amides.…”