Enantioselective reductive multicomponent coupling reactions between isatins and aldehydes

Abstract

A metal-free stereoselective reductive coupling reaction between isatins and aldehydes is reported. The reaction relies on commercial diethyl phosphite (∼€70 kg−1) as the stoichiometric reductant. Base-catalyzed Pudovik addition and phosphonate/phosphate rearrangement achieved polarity inversion on the isatin, and the derived carbanions were trapped by aldehydes with subsequent dialkoxyphosphinyl migration. Chiral iminophosphoranes were used as basic catalysts to achieve high diastereo- and enantioselectivities with excellent yields.

Organocatalytic Arylation of α‐Ketoesters Based on Umpolung Strategy: Phosphazene‐Catalyzed SNAr Reaction Utilizing [1,2]‐Phospha‐Brook Rearrangement

“…Furthermore, we have recently developed an “umpolung” intramolecular cyclization that involves the catalytic generation of α‐aminocarbanions from imines . The enantioselective addition reactions of enolates derived from isatins and benzylidene pyruvates were developed by groups of Johnson and Ooi, which also emphasized the usability of the methodology ,. During the course of our studies, we have envisioned the development of a catalytic carbon–carbon bond‐forming reaction that differs from the nucleophilic addition reaction, with the aim of expanding the scope of the applicable transformation of carbanions generated through the formal umpolung process.…”

Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition

“…1) structurally related to P2- t -Bu phosphazene, which are known to be substantially more basic than trialkylamines [34]. With C1 [34–38] and C2 [39–55], we observed no product formation, presumably due to insufficient basicity. Though C3 [30,56–57] led to partial conversion of starting material, no appreciable enantioselectivity was observed.…”

Synthesis ofα‐Hydroxyphosphonates Containing Functionalized 1,2,3‐Triazoles

“…Among the different reactions involving hydrophosphoryl compounds, [19–25] the synthesis of α ‐ and β ‐hydroxyphosphonates by the Abramov and the Pudovik reactions have gained significant attention, because of their mild conditions and high atom‐economy [26–31] . Abramov is a method which involves the reaction between hydrophosphoryl reagent with carbonyl compounds, while Pudovik is related to the nucleophilic attack to an imine organic function.…”