Carbene and Acid Cooperative Catalytic Reactions of Aldehydes and o-Hydroxybenzhydryl Amines for Highly Enantioselective Access to Dihydrocoumarins

Abstract

A highly enantioselective method for quick access to dihydrocoumarins is reported. The reaction involves a cooperative catalytic process with carbene and in situ generated Brønsted acid as the catalysts. α-Chloro aldehyde and readily available and stable o-hydroxybenzhydryl amine substrates were used to generate reactive azolium ester enolate and ortho-quinone methide (o-QM) intermediates, respectively, to form dihydrocoumarins with exceptionally high diastereo- and enantioselectivities. The catalytic reaction products can be easily transformed to valuable pharmaceuticals and bioactive molecules.

Synthesis and Antioxidant Capacity of Some Derivatives of Sesamol at the C‐6 Position

“…The results obtained on the substitution in the indicated position are also consistent with the literature on other previously obtained mono‐C‐6‐derivatives of sesamol, such as kakuol and its analogs, [25] Mannich and Betti bases [26–32] diarylbutanes, [33] (het)arylpyrrolidines, [34] allylsesamol [35] …”

Chiral Inductive Diastereoconvergent Allylation Reactions of Allyltrimethylsilane and Diastereomixtures of Diarylmethanols Catalyzed by FeCl3

“…When the cinnamylation reaction of diarylmethanol 8a with cinnamyltrimethylsilane ( 16 ) was performed under the optimized conditions, the reaction also proceeded with γ‐selectivity to furnish the desired compound 15 efficiently. We further attempted the transformation of the cinnamylated product 15 into 3,4‐diphenylcoumarin 19 , which is contained in the biologically important structure (Scheme ). The lactol 18 was synthesized via the removal of the chiral auxiliary 15 followed by the ozonolysis of the olefin 17 in the same manner as the above‐mentioned synthesis of ( R )‐tolterodine ( 1 ).…”

Recent Advances in Organocatalytic Asymmetric Cycloaddition Reactions Through Ortho‐Quinone Methide Scaffolds

“…These unique Lewis bases are used to catalyze the formation of acyl anions, enoates and homoenoates. [55] In 2017, Chi and co-workers [56]…”

“…These unique Lewis bases are used to catalyze the formation of acyl anions, enoates and homoenoates [55] . In 2017, Chi and co‐workers [56] reported a carbene catalyzed reaction of α ‐chloro aldehyde 174 and o ‐hydroxybenzhydryl amine 173 (Scheme 35a). The reaction of carbene catalyst 175 with α ‐chloro aldehyde substrate 174 gave an azolium ester enolate intermediate 174’ , which in situ generated a Brønsted acid (HOAc) as the co‐catalyst to activate diarylmethyl amine 173 .…”