Anion-binding catalyst designs for enantioselective synthesis

Stereodivergent Anion Binding Catalysis with Molecular Motors

“…Asymmetric anion binding catalysis is based on the activation of an ion pair for the attack of a nucleophile through the recognition of the anion by a chiral receptor . Since the groundbreaking reports by Jacobsen and co‐workers on the use of chiral thioureas as the anion binding catalysts, several other classes of anion receptors have been designed and successfully applied in asymmetric catalysis . Herein, we report on the use of a molecular motor‐based stimuli‐responsive anion receptor to illustrate the concept of adaptive stereodivergent anion binding catalysis, which is achieved by means of supramolecular transfer of chirality (Figure ).…”

“…[14] Since the groundbreaking reports by Jacobsen and co-workers on the use of chiral thioureas as the anion binding catalysts, [15] several other classes of anion receptors have been designed and successfully applied in asymmetric catalysis. [16] Herein, we report on the use of am olecular motor-based stimuliresponsive anion receptor to illustrate the concept of adaptive stereodivergent anion binding catalysis,which is achieved by means of supramolecular transfer of chirality (Figure 1). The precise positioning of two ion binders with respect to each other at each stage of the rotation cycle of the motor creates different chiral environments at the anion recognition site, which translates into different stereochemical outcomes in anion binding catalysis.Tr iazoles have been recognized as amide surrogate anion binders due to their dipole moment (ca.…”

Mechanism and origins of selectivity in the enantioselective oxa-Pictet–Spengler reaction: a cooperative catalytic complex from a hydrogen bond donor and chiral phosphoric acid

“…16 This principle has been demonstrated to great effect in the context of nucleophilic additions to iminium ions (e.g., Jacobsen's asymmetric Strecker and Pictet-Spengler reactions) and for cyclic or stabilized oxocarbenium ions. [17][18][19][20][21][22][23][24][25][26] Particularly prominent among organocatalysts are the CPAs. 27 Since the seminal reports of Akiyama 28 and Terada, 29 CPAs have been successfully applied to a diverse range of reactions.…”

A Cooperative Hydrogen Bond Donor–Brønsted Acid System for the Enantioselective Synthesis of Tetrahydropyrans

“…[3] Pioneering work by Jacobsen detailed the ability of ureabased chiral anion-receptor catalysts to promote the enantioselective addition of silyl ketene acetals to oxocarbenium ions generated in situ. [5] Brønsted and Lewis acid catalysis are alternative approaches to generate chiral oxocarbenium ions,t hough the majority of these have similar limitations as anion-binding catalysis,o ra re constrained to cyclic frameworks. [5] Brønsted and Lewis acid catalysis are alternative approaches to generate chiral oxocarbenium ions,t hough the majority of these have similar limitations as anion-binding catalysis,o ra re constrained to cyclic frameworks.…”

“…[4] This report has been followed by several applications of chiral anion-binding catalysts in asymmetric reactions invoking oxocarbenium ion intermediates,t hough these reports are only known to be compatible with substrates that produce stabilized, conjugated ionic intermediates (such as benzylic or aromatic (pyrylium)-type intermediates). [5] Brønsted and Lewis acid catalysis are alternative approaches to generate chiral oxocarbenium ions,t hough the majority of these have similar limitations as anion-binding catalysis,o ra re constrained to cyclic frameworks. [6] Notable exceptions include the use of novel highly constrained chiral imidodiphosphate-derived Brønsted acid catalysts pioneered by List, which uniquely engage non-stabilized oxocarbenium precursors in some cases through sequestration of the reactive intermediate.…”