Controllable Rh(III)-Catalyzed Annulation between Salicylaldehydes and Diazo Compounds: Divergent Synthesis of Chromones and Benzofurans

Abstract

A Rh(III)-catalyzed annulation between salicylaldehydes and diazo compounds with controllable chemoselectivity is described. AgNTf favored benzofurans via a tandem C-H activation/decarbonylation/annulation process, while AcOH led to chromones through a C-H activation/annulation pathway. The reaction exhibited good functional group tolerance and scalability. Moreover, only a single regioisomer of benzofuran was obtained due to the in situ decarbonylation orientation effect.

Divergent Coupling of Benzocyclobutenones with Indoles via C−H and C−C Activations

“…Addition of AgTFA further improved the yield of 5 a (Table 2, entries 5-7). [12] Further optimization revealed that the temperature has an obvious influence on the yield, but no impact on the selectivity, as the same with the observation in Ni and Ru catalyzed conditions. [10] Figure 2.…”

Rh(III)-Catalyzed Annulation of Boc-Protected Benzamides with Diazo Compounds: Approach to Isocoumarins

“…Diazo substrates were synthesized from the corresponding ketonic esters or 1,3 di-ketones as shown in Scheme S1. 2a – 2o was synthesized according to the literatures [36].…”

Realizing the Trifunctional Potential of Alkyl 4-Chloro-2-diazo-3-oxobutanoates: Convenient Assembly of 6,7-Dihydro-4H-[1,2,3]triazolo[5,1-c][1,4]thiazine Core

“…Compound 1 is rather densely functionalized, containing four contiguous potentially reactive centers: a labile chlorine, a ketone carbonyl, a diazo group, and an ester. It is therefore quite surprising that, according to literature reports, this reagent was mostly employed as a bifunctional -diazocarbonyl compound: in the synthesis of isocoumarins and -pyrones 7 as well as isoquinolones and pyridines 8 from benzamides (involving Rh III -catalyzed carbene C-H insertion), rather similar access to isoquinolines from arylimidates, 9 divergent synthesis of chromones and benzofurans via Rh III -catalyzed annulation of salicylaldehyde 10 and a series of related annulation reactions were reported in the last two years. [11][12][13] Treatment of 1 as bifunctional -diazocarbonyl reagent is showcased in its Rh II -catalyzed condensation with benzamides to give oxazoles 14 and Rh II -catalyzed 1,3-dipolar cycloaddition with enol ethers.…”