Chiral Boro‐Phosphate Catalyzed Asymmetric Transfer Hydrogenation of 1‐Enal Substituted 2‐Naphthols: Access to Axially Chiral Styrene‐Type Allylalcohols

Abstract

Herein, we present a chiral borophosphate catalyzed atroposelective asymmetric transfer hydrogenation method, leading to a family of axially chiral styrene-type allylalcohols. This dynamic kinetic resolution approach portrays simple procedure, mild conditions and good enantiocontrol (51-95% ee), thus providing an important alternative to assemble the challenging atropisomeric arylacyclic alkene scaffolds.

Organocatalytic Atroposelective Dynamic Kinetic Resolution Involving Ring Manipulations

“…To further explore the potential of substrate 32 in atroposelective DKR and offer a useful platform for assembling structurally diverse aryl-acyclic alkene atropisomers, we recently applying the strategy of chiral boro-phosphate mediated asymmetric reduction to realize DKR of 1-enal substituted 2-naphthols 32, thereby rendering a straightforward entry to enantioenriched axially chiral styrene-type allylalcohols (Scheme 15). [45] The BINOL-derived CPA Cat. 12*, with a very bulky 2,4,6-tricyclohexylphenyl group in the 3,3'-position, was identified as the best choice to promote the designed asymmetric transfer hydrogenation (ATH) reaction of 1-enal substituted 2-naphthols 32 with pinacol borane (HBPin) as the hydride source, leading to a family of novel axially chiral styrene-type allylalcohols 37 in 52-94% yields with good to high enantioselectivities (51-95% ee).…”

Development of Configurationally Labile Biaryl Reagents for Atropisomer Synthesis

“…The same group also reported an atroposelective transfer hydrogenation using chiral phosphoric acid catalysts, providing a new family of axially chiral tetra-ortho-substituted styrene-type allyl alcohols (Scheme 23b). [82] The dynamic kinetic resolution process was realized through the five-membered cyclic O,O-acetal inter- mediates. Wang, Su, and co-workers developed a peptidephosphonium salt-catalyzed asymmetric nucleophilic aromatic substitution reaction of aldehyde-substituted styrenes involving a dynamic kinetic resolution process via a five-membered lactol intermediate, furnishing a series of axially chiral tetra-orthosubstituted aldehyde-containing styrenes in high yields and enantioselectivities (Scheme 23c).…”

Dynamic kinetic resolution of atropisomeric N-arylindoles via chiral N-triflyl phosphoramide catalyzed asymmetric reductive amination

“…Collectively, further development of new methodologies to assemble axially chiral N-arylindoles is still highly desirable. Inspired by our recent findings regarding the DKR of aryl-acyclic alkene atropisomers by virtue of configurationally unstable cyclic intermediates, 13,24 we wondered if DKR-ARA would be applicable to forge the C-N axis in arylindoles. Herein, we report an atroposelective DKR-ARA of N-arylindole aldehydes 1 using chiral N-triflyl phosphoramide 25 as a chiral Brønsted acid (CBA) catalyst, rendering a new entry to enantioenriched N-arylindoles.…”