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Relevant academic research and scientific papers

Catalytic asymmetric epoxidation of α,β-unsaturated N-acylpyrroles as monodentate and activated ester equivalent acceptors

Catalytic asymmetric epoxidation of α,β-unsaturated N-acylpyrroles as monodentate and activated ester equivalent acceptors is described. A Sm(O-i-Pr)3/(R)-H8-BINOL complex promoted the epoxidation reaction to afford products in high yield (up to quant) and high enantiomeric excess (up to >99.5% ee). Reaction proceeded smoothly using cumene hydroperoxide (CMHP) with low explosive hazard, and completed within 0.2-0.5 h with 5 mol % catalyst. Catalyst loading was successfully reduced to as little as 0.02 mol %. The N-acylpyrrole properties as well as efficient synthesis of α,β-unsaturated N-acylpyrroles are also described.

Catalytic asymmetric 1,4-addition reactions using α,β- unsaturated N-acylpyrroles as highly reactive monodentate α,β- unsaturated ester surrogates

Synthesis and application of α,β-unsaturated N-acylpyrroles as highly reactive, monodentate ester surrogates in the catalytic asymmetric epoxidation and Michael reactions are described. α,β-Unsaturated N-acylpyrroles with various functional groups were synthesized by the Wittig reaction using ylide 2. A Sm(O-i-Pr)3/H8-BINOL complex was the most effective catalyst for the epoxidation to afford pyrrolyl epoxides in up to 100% yield and >99% ee. Catalyst loading was successfully reduced to as little as 0.02 mol % (substrate/catalyst = 5000). The high turnover frequency and high volumetric productivity of the present reaction are also noteworthy. In addition, a sequential Wittig olefination-catatytic asymmetric epoxidation reaction was developed, providing efficient one-pot access to optically active epoxides from various aldehydes in high yield and ee (96→99%). In a direct catalytic asymmetric Michael reaction of hydroxyketone promoted by the Et 2Zn/linked-BINOL complex, Michael adducts were obtained in good yield (74-97%), dr (69/31-95/5), and ee (73-95%). This represents the first direct catalytic asymmetric Michael reaction of unmodified ketone to an α,β-unsaturated carboxylic acid derivative. The properties of α,β-unsaturated N-acylpyrrole are also discussed. Finally, the utility of the N-acylpyrrole unit for further transformations is demonstrated.

Sequential Wittig olefination-catalytic asymmetric epoxidation with reuse of waste Ph3P(O): Application of α,β-unsaturated N-Acyl pyrroles as ester surrogates

Waste not, want not: Efficient one-pot access to optically active epoxides with 96 to 99.5% ee from a variety of aldehydes is described. In a sequential process, the Ph3P(O) by-product of a Wittig reaction acts as a modulator for the samarium catalyst in the asymmetric epoxidation of the conjugated N-acyl pyrrole Wittig product (see scheme). The N-acyl pyrrole functionality is key to the high reactivity and selectivity observed. R = alkyl, aryl, vinyl.