Asymmetric hydrogenation and transfer hydrogenation in the enantioselective synthesis of flavonoids

Abstract

Asymmetric hydrogenation (AH) and asymmetric transfer hydrogenation (ATH) are versatile synthetic methodologies widely employed in the preparation of chiral compounds. In this review, we explore the applications of AH and...

Ru(II)-Catalyzed Asymmetric Transfer Hydrogenation of Chalcones in Water: Application to the Enantioselective Synthesis of Flavans BW683C and Tephrowatsin E

“…The reactivity increase observed for this 2′-OH chalcone could be explained by the intramolecular hydrogen bonding between the carbonyl group and the peri-OH group, which acts as a Brønsted acid, lowering the enone's LUMO energy and increasing its electrophilicity. 4,27 This interaction also seems to have a positive effect on the chemoselectivity, leading to 1,3-diarylpropan-1-ol (R)-6a without the formation of the allylic alcohol.…”

“…These chiral alcohols are bioactive natural products also isolated from plants that produce flavans, suggesting a biosynthetic relationship . Furthermore, 1,3-diarylpropan-1-ols bearing a 2-OH group at ring B are known as key synthetic intermediates for the synthesis of flavans through Mitsunobu cyclization. , Thus, we hypothesized that the one-pot CC/CO reduction of chalcones through a Ru-catalyzed ATH could stand out as a convenient alternative for the preparation of these intermediates, allowing the enantioselective synthesis of flavans in two steps from readily accessible substrates (Scheme c).…”

“…8 Furthermore, 1,3diarylpropan-1-ols bearing a 2-OH group at ring B are known as key synthetic intermediates for the synthesis of flavans through Mitsunobu cyclization. 4,9 Thus, we hypothesized that the one-pot C�C/C�O reduction of chalcones through a Ru-catalyzed ATH could stand out as a convenient alternative for the preparation of these intermediates, allowing the enantioselective synthesis of flavans in two steps from readily accessible substrates (Scheme 1c). The Noyori−Ikariya type complexes (Figure 1) are among the most successful catalysts used for the ATH of a wide variety of ketones.…”

Asymmetric Hydrogenation by Relay Catalysis with FLPs and CPAs: Stereodivergent Synthesis of 3-Substituted Flavanones

“…Chiral flavanone and chromanone moieties are widely present in natural products and pharmaceutically or biologically active molecules . Their syntheses have been receiving considerable attention, and various enantioselective methods have been successfully developed . The transition-metal-catalyzed asymmetric hydrogenation of unsaturated compounds has been quite successful in the past half-century.…”

Asymmetric Transfer Hydrogenation of 2,3-Disubstituted Flavanones through Dynamic Kinetic Resolution Enabled by Retro-Oxa-Michael Addition: Construction of Three Contiguous Stereogenic Centers

“…Chiral flavanol derivatives constitute a large class of important molecules and feature a variety of useful bioactivities (Figure ) such as antiviral, antibacterial, and antifungal effects . Although substantial progresses have been gained on the synthesis of chiral flavanols, some of them are limited in substrate scope and catalyst efficiency. The construction of functionalized flavanols with three chiral centers is still a challenge in synthetic organic chemistry.…”