Three-component acyloxylation of diazo compounds with carboxylic acids and azadienes

Abstract

Despite many studies on benzofuran-derived azadiene have been reported, multi-component studies have scarcely been reported on this heterocyclic skeleton. The first cascade three-component acyloxylation of diazos with acids and azadienes...

Theoretical Analysis of a Three-Component Reaction between Two Diazo Compounds and a Hydroxylamine Derivative: Mechanism, Enantioselectivity, and Effect of Cooperative Catalysis

“…As shown by the purple line (Figure 2), the ammonium ylide A-1a may also be transformed into the enol A-2a-2 via a BnOH-assisted [1,4]-H shift (A-TSa2-2), which requires an activation free energy of 1.9 kcal/mol. The following BnOH-assisted [1,3]-H shift of A-2a-2 with a 26.8 kcal/mol barrier (A-TSa3-2) also leads to N−H insertion product A-3a-1. Both N−H insertion pathways were calculated and shown to be energetically unfavorable.…”

“…At the same time, two other possible pathways were also considered, involving the commonly recommended N−H insertion of Rh carbenes (Figure 2). As shown by the red line in Figure 2, an ion pair intermediate A-2a may also undergo a BnOH-assisted [1,2]-H shift after the dissociation of Rh 2 (OAc) 4 , via transition state A-TSa3-3 with a 21.3 kcal/mol barrier, resulting in N−H insertion product A-3a-1. Furthermore, the elimination of BnOH from A-3a-1 to produce A-3a requires 35.5 kcal/mol (A-TSa4-2), which is energetically unfeasible at a temperature of −20 °C.…”

“…14 Based on our previous work, 15 a new pathway including the [1,4]-H shift was proposed that can lead to the formation of an enol complex B-2a. The calculated free energy of activation for this [1,4]-H shift based on the oxonium ylide is only 1.5 kcal/mol. And B-2a is more stable than B-1a by −8.2 kcal/mol.…”

“…Diazo compounds are commonly used as highly reactive and multifunctional building blocks in organic synthesis, which commonly involves different types of metal-containing active species. 1 One such example includes metal carbene complexes that are currently acknowledged as one of the hot topics of homogeneous catalysis for organic synthesis. 2 Besides, hydroxylamines represent easily available, versatile, and popular starting materials for applications in synthetic organic chemistry.…”

Construction of α-Acyloxy Ketones via Photoredox-Catalyzed O–H Insertion of Sulfoxonium Ylides with Carboxylic Acids

“…First, the protonation of diazoalkane followed by nucleophilic attack of carboxylate can afford the O–H insertion product (Scheme a) . Second, the formation of transition-metal carbenoids via denitrogenation of diazo compounds catalyzed by appropriate transition-metal catalysts followed by nucleophilic attack of carboxylic acids has been well documented for realizing O–H insertion reactions (Scheme b). − Third, an organic Lewis acid (tropylium)-catalyzed O–H functionalization of diazoalkanes with carboxylic acids has been reported by Koenigs and co-workers (Scheme c) . Moreover, the involvement of a free carbene intermediate, produced by photolytic activation of diazo compounds, in performing O–H insertion with carboxylic acids has also advanced (Scheme d). , …”