Photo-organocatalytic enantioselective α-hydroxylation of β-keto esters and β-keto amides with oxygen under phase transfer catalysis

Abstract

An efficient and enantioselective photo-organocatalytic α-hydroxylation of β-dicarbonyl compounds using molecular oxygen was extended.

Controlling Photooxygenation with a Bifunctional Quinine‐BODIPY Catalyst: towards Asymmetric Hydroxylation of β‐Dicarbonyl Compounds

“…In 2012, the group of Meng described enantioselective photooxygenations by phase‐transfer catalysis . The authors focused their work on the hydroxylation of a series of indanone‐ and tetralone‐derived β‐keto esters and β‐keto amides . Besides organocatalytic strategies, the group of Xiao reported in 2017 the preparation of bifunctional photocatalysts for enantioselective aerobic oxidation of β‐keto esters, mainly derived from indanone .…”

Aerobic Oxidations in Asymmetric Synthesis: Catalytic Strategies and Recent Developments

“…The method can be considered as complementary to the Ni-mediated transformation developed by the Xiao group (Scheme 9) (Ding et al, 2017). For example, the aerobic oxidation of SCHEME 19 | Enantioselective α-hydroxylations of carbonyl compounds with singlet oxygen (Sundén et al, 2004;Ibrahem et al, 2006 ester 74 furnished hydroxylation product 24a in 98% yield and 90% ee in the presence of 2.5 mol% of phase transfer catalyst 75 (Scheme 20) (Wang et al, 2016). The reaction conditions are mild, being applicable for a range of the β-carbonyl compounds (30 examples in total).…”

“…Works of the Meng group represent a notable recent example of chirality induction in the α-hydroxylation reactions by means of phase transfer catalysis and visible light activation of dioxygen ( Lian et al, 2012 ; Wang et al, 2016 ; Tang et al, 2018 ; Tang et al, 2019a ; Tang et al, 2019b ). The method can be considered as complementary to the Ni-mediated transformation developed by the Xiao group ( Scheme 9 ) ( Ding et al, 2017 ).…”

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

“…They reported the preparation of indanone-α-hydroxy-β-keto esters in 81-93% yields and 39-75% ee (Scheme 41). The mechanism of this reaction involves the attack of the enolate paired with the chiral counter ion PTC to the singlet oxygen electrophile to give the hydroper- Later, these results were improved by the development of a new chiral PTC and re-optimization of the experimental conditions [92]. The new protocol furnished the indanone derivatives in 70-99% yields and 62-90% ee.…”