Catalytic asymmetric Meerwein–Ponndorf–Verley reduction of glyoxylates induced by a chiral N,N′-dioxide/Y(OTf)₃complex

Abstract

An asymmetric Meerwein-Ponndorf-Verley (MPV) reduction of glyoxylates was for the first time accomplished via an N,N'-dioxide/Y(OTf) complex with aluminium alkoxide and molecular sieves (MSs) as crucial additives. A variety of optically active α-hydroxyesters were obtained with excellent results. A possible reaction mechanism was proposed based on the experiments.

Boron-Catalyzed Azide Insertion of α-Aryl α-Diazoesters

“…After washing with brine solution, the combined organic extracts were dried over Na 2 SO 4 and concentrated by rotary evaporation. The residue was purified by flash chromatography (petroleum ether/ethyl acetate = 10:1) to afford the protected intermediate as a clear oily liquid (2.108g, 78%) yield …”

“…The residue was purified by flash chromatography (petroleum ether/ethyl acetate = 10:1) to afford the protected intermediate as a clear oily liquid (2.108g, 78%) yield. 24 The next step was followed by the general procedure for the synthesis of 1 (3 mmol scale). Isolated yield: orange oil; 596.0 mg, 67% yield.…”

Scandium Triflate Catalyzed Tandem Transfer Hydrogenation and Cyclization Reaction of o-Aminobenzaldehydes and o-Aminoacetophenone with Alcohols

“…Generally, the MPV reduction mechanism involves intermolecular hydride transfer from sacrificial alcohols to carbonyl compounds via a six-membered ring transition state . Owing to its carbonyl-specific chemoselectivity and environmentally friendly process, intensive efforts to develop various catalytic systems of MPV reduction have been made, − such as inorganic bases, boron alkoxides, and transition-metal systems. , So far, scandium is rarely used as a metal catalyst for the MPV reaction . Sc­(OTf) 3 is an environmentally friendly Lewis acid and had shown widespread application in organic transformation .…”

“…Despite these prominent advances of the MPV reaction, the principal challenges for further improving such reduction are still noticeable. Designing a new method for the MPV reduction by any primary and secondary alcohols that can be used as a hydride source, rather than using a secondary alcohol such as 2-propanol, is highly desirable. − …”

A porous inorganic zirconyl pyrophosphate as an efficient catalyst for the catalytic transfer hydrogenation of ethyl levulinate to γ‐valerolactone

“…Wu et al introduced a chiral N , N ‐dioxide/Y(OTf) 3 complex to bring about the reduction of glycosylates. It was found that the adjunction of both molecular sieves and Al(OtBu) 3 was effective for the reaction . There are many catalysts used in the CTH reaction, but for this kind of reaction there still exist limiting factors, such as a high reaction temperature, a long reaction time, complex operation of the catalyst preparation process, and expensive catalyst materials.…”