Highly Enantioselective One-Pot Synthesis of Chiral β-Hydroxy Sulfones via Asymmetric Transfer Hydrogenation in an Aqueous Medium

Highly efficient synthesis of enantioenriched vicinal halohydrins via Ir-catalyzed asymmetric hydrogenation using dynamic kinetic resolution

A novel synthetic route was developed for the construction of chiral cis-vicinal halohydrins derivatives through Ir/f-phamidol-catalysed asymmetric hydrogenation of corresponding α-halogenated ketones with high yields (up to 99% yield), excellent diastereoselectivities (>20 : 1 dr), enantioselectivities (up to 99% ee), and high substrate catalyst ratio (S/C = 1000).

Asymmetric transfer hydrogenation of boronic acid pinacol ester (Bpin)-containing acetophenones

A series of Bpin-containing acetophenone derivatives were reduced by asymmetric transfer hydrogenation (ATH), using Noyori-Ikariya catalysts, with formic acid/triethylamine, to alcohols in high ee when the Bpin is in the para- or meta-position. Substrates containing ortho-Bpin groups were reduced in lower ee, with formation of a cyclic boron-containing group. The products were converted to substituted derivatives using Pd-catalysed coupling reactions. The results represent the first examples of ATH of Bpin-containing ketones.

Chemoenzymatic Oxosulfonylation-Bioreduction Sequence for the Stereoselective Synthesis of β-Hydroxy Sulfones

A series of optically active β-hydroxy sulfones has been obtained through an oxosulfonylation-stereoselective reduction sequence in aqueous medium. Firstly, β-keto sulfones were synthesized from arylacetylenes and sodium sulfinates to subsequently develop the carbonyl reduction in a highly selective fashion using alcohol dehydrogenases as biocatalysts. Optimization of the chemical oxosulfonylation reaction was investigated, finding inexpensive iron(III) chloride hexahydrate (FeCl3  ⋅ 6H2 O) as the catalyst of choice. The selection of isopropanol in the alcohol-water media resulted in high compatibility with the enzymatic process for enzyme cofactor recycling purposes, providing a straightforward access to both (R)- and (S)-β-hydroxy sulfones. The practical usefulness of this transformation was illustrated by describing the synthesis of a chiral intermediate of Apremilast. Interestingly, the development of a chemoenzymatic cascade approach avoided the isolation of β-keto sulfone intermediates, which allowed the preparation of chiral β-hydroxy sulfones in high conversion values (83-94 %) and excellent optical purities (94 to >99 % ee).

Efficient synthesis of an apremilast precursor and chiral β-hydroxy sulfones via ketoreductase-catalyzed asymmetric reduction

Ketoreductase (KRED)-catalyzed asymmetric reduction of prochiral ketones is an attractive method to synthesize chiral alcohols. Herein, two KREDs LfSDR1-V186A/E141I and CgKR1-F92I with complementary stereopreference were identified towards reduction of apremilast prochiral ketone intermediate 1a. LfSDR1-V186A/E141I exhibited >99% conversion and 99.2% ee yielding an apremilast chiral alcohol intermediate ((R)-2a) at 50 g L-1 substrate loading. Furthermore, we investigated the substrate scope of β-keto sulfones by using LfSDR1-V186A/E141I and CgKR1-F92I to produce both enantiomers of the corresponding β-hydroxy sulfones, with good-to-excellent conversion (up to >99%) and enantioselectivity (up to 99.9% ee) being obtained in most cases. Finally, the gram-scale synthesis of (R)-2a was performed by employing the crude enzyme of LfSDR1-V186A/E141I and BsGDH to afford the desired enantiomer with >99% conversion, 85.9% isolated yield and 99.2% ee. This study presents a biocatalytic strategy to synthesize chiral β-hydroxy sulfones.

One-pot enantioselective construction of 3,4-dihydro-2H-1,4-oxazines over Ru/Au relay catalysis and its mechanistic serendipity

One-pot enantioselective construction of 3,4-dihydro-2H-1,4-oxazines have been developed through the transfer hydrogenation/cyclization enantio-relay process using Ru and Au bimetallic catalysts.

Recent Progress on the Synthesis of Chiral Sulfones

Chiral sulfones extensively exist in drugs, agricultural chemicals, chiral organic intermediates, and functional materials. Their importance causes the rapid development of their synthetic methods in recent years. Many transition metal complex catalysts with chiral ligands and chiral organocatalysts are adopted in synthesis of chiral sulfones. Most of the methods to construct chiral sulfones are based on the reduction of unsaturated sulfones and the introduction of sulfone groups into unsaturated hydrocarbons. This review describes all classes of asymmetric reactions for synthesis of chiral sulfones.

Synthesis and applications of sodium sulfinates (RSO2Na): a powerful building block for the synthesis of organosulfur compounds

This review highlights the preparation of sodium sulfinates (RSO2Na) and their multifaceted synthetic applications. Substantial progress has been made over the last decade in the utilization of sodium sulfinates emerging as sulfonylating, sulfenylating or sulfinylating reagents, depending on reaction conditions. Sodium sulfinates act as versatile building blocks for preparing many valuable organosulfur compounds through S-S, N-S, and C-S bond-forming reactions. Remarkable advancement has been made in synthesizing thiosulfonates, sulfonamides, sulfides, and sulfones, including vinyl sulfones, allyl sulfones, and β-keto sulfones. The significant achievement of developing sulfonyl radical-triggered ring-closing sulfonylation and multicomponent reactions is also thoroughly discussed. Of note, the most promising site-selective C-H sulfonylation, photoredox catalytic transformations and electrochemical synthesis of sodium sulfinates are also demonstrated. Holistically, this review provides a unique and comprehensive overview of sodium sulfinates, which summarizes 355 core references up to March 2020. The chemistry of sodium sulfinate salts is divided into several sections based on the classes of sulfur-containing compounds with some critical mechanistic insights that are also disclosed.

Sulfone Group as a Versatile and Removable Directing Group for Asymmetric Transfer Hydrogenation of Ketones

The sulfone functional group has a strong capacity to direct the asymmetric transfer hydrogenation (ATH) of ketones in the presence of [(arene)Ru(TsDPEN)H] complexes by adopting a position distal to the η6 -arene ring. This preference provides a means for the prediction of the sense of asymmetric reduction. The sulfone group also facilitates the formation of a range of reduction substrates, and its ready removal provides a route to enantiomerically enriched alcohols that would otherwise be extremely difficult to prepare by direct ATH of the corresponding ketones.

Temperature-dependent synthesis of vinyl sulfones and β-hydroxy sulfones from t-butylsulfinamide and alkenes under aerobic conditions

A novel strategy was developed for the synthesis of organic sulfones using t-butylsulfinamide as a sulfur source.

Efficient synthesis of chiral β-hydroxy sulfones via iridium-catalyzed hydrogenation

A highly efficient Ir-catalyzed asymmetric hydrogenation of prochiral β-keto sulfones was successfully developed, affording a series of chiral β-hydroxy sulfones with excellent results (up to >99% conversion, 99% yield, >99% ee, and 20 000 TON).

Highly Enantioselective One-Pot Synthesis of Chiral β-Heterosubstituted Alcohols via Ruthenium-Prolinamide-Catalyzed Asymmetric Transfer Hydrogenation

The utility of a chiral Ru-prolinamide catalytic system has been demonstrated in one-pot synthesis of optically active β-triazolylethanol and β-hydroxy sulfone derivatives. The said methodology proceeds through asymmetric transfer hydrogenation of in situ formed ketones of the corresponding chiral products. Various chiral prolinamide ligands were screened, and ligand L6 with isopropyl groups substituted at the ortho position has shown excellent activity at 60 °C in aqueous medium producing up to 95% yield and 99.9% enantioselectivity.

One-Pot Synthesis of β-Hydroxysulfones and Its Application in the Preparation of Anticancer Drug Bicalutamide

An efficient one-pot multistep strategy has been developed, comprising auto-oxidative difunctionalization of alkenes, oxidation of sulfides, and a further reduction of peroxides for the synthesis of complex β-hydroxysulfone derivatives from phenthiols and alkenes. This method has several advantageous characteristics, including readily available substrates, low-cost and environmental benign reagents, nontoxic and renewable solvents, and mild reaction conditions. The application of this transformation to the multigram-scale preparation of the anticancer drug bicalutamide is accomplished.

A dynamic kinetic asymmetric transfer hydrogenation–cyclization tandem reaction: an easy access to chiral 3,4-dihydro-2H-pyran-carbonitriles

A catalytic enantioselective dynamic kinetic asymmetric transfer hydrogenation–cyclization tandem reaction is developed for 1,3-difunctionalized racemic ketones.

One-pot synthesis of optically pure β-hydroxy sulfones via a heterogeneous ruthenium/diamine-promoted nucleophilic substitution-asymmetric transfer hydrogenation tandem process

Chiral ruthenium/diamine-functionalized mesoporous silica is synthesized and its application in the one-pot synthesis of chiral β-hydroxy sulfones is investigated.

Highly enantioselective asymmetric transfer hydrogenation (ATH) of α-phthalimide ketones

A mild catalyst system for the synthesis of chiral amino alcohols via asymmetric transfer hydrogenation (ATH) of α-phthalimide ketones has been developed by using a chiral Ru-TsDPEN complex as the catalyst in DMF/MeOH at 40 °C. The reaction exhibits high reaction activity and excellent enantioselectivity where up to 96% yield and 99% ee of the product were obtained.

Asymmetric transfer hydrogenation of γ-aryl α,γ-dioxo-butyric acid esters

Six ferrocene-based chiral ligands were prepared and applied in ATH reaction of multiple-carbonyl compounds as RuCl(p-cymene)[Ts-DPEN] did.

Hg/Pt-catalyzed conversion of bromo alkynamines/alkynols to saturated and unsaturated γ-butyrolactams/lactones via intramolecular electrophilic cyclization

Convenient and general Hg(ii)/Pt(iv) catalyzed syntheses of γ-butyrolactams and α,β-unsaturated γ-butyrolactones/lactams are described via intramolecular electrophilic cyclizations of bromoalkynes with tosylamino and hydroxyl tethers. The reaction features the use of wet solvents, the exclusion of any base and additive, mild conditions and practical yields. We also synthesised few chiral lactams through this pathway. Additionally, it is shown that the NHTs group distanced further from the homopropargylic position assists regioselective bromoalkyne hydration to yield useful α-bromoketones. Furthermore, Boc protected bromo homo propargyl amines undergo 6-endo-dig cyclization through Boc oxygen to give bromomethylene substituted oxazinones.