Transition Metal Free Chemoselective Reduction of α,β‐Unsaturated Ketones to Saturated Ketones Using Tosyl Hydrazide as a Hydrogen Donor

An efficient, inexpensive and simple method for the reduction of various α,β‐unsaturated ketones to corresponding saturated ketones using tosyl hydrazide as a hydrogen donor in DMF using calcium oxide powder has been reported. A variety of enones underwent reduction without forming undesirable side products. High chemoselectivity, broad functional group tolerance and good yields are the noteworthy features of this protocol.     

Synthesis of Phenanthrene Derivatives through the Reaction of an α,α‐Dicyanoolefin with α,β‐Unsaturated Carbonyl Compounds

Phenanthrene derivatives were prepared by reacting an α,α‐dicyanoolefin with different α,β‐unsaturated carbonyl compounds resulting from Wittig reaction of ninhydrin and phosphanylidene or condensation of barbituric acid and an aldehyde. The easy procedure, mild and metal‐catalyst free, reaction conditions, good yields, and no need for chromatographic purifications are important features of this protocol. The structures of the product of type 3 and 5 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS). A plausible mechanism for this type of reaction is proposed (Scheme 1).     

Synthesis of β‐Haloketones by β‐Addition Reactions of α,β‐Unsaturated Ketones with BX3 (X = Br,Cl) as Halide Source

A series of β‐bromoketones and β‐chloroketones were synthesized by the addition reactions of α,β‐unsaturated ketones under BX₃ (X = Br, Cl) and ethylene glycol reaction system. The α,β‐unsaturated ester also was successfully converted to its corresponding β‐bromoester under the reaction condition.     

Hydrogenation of β-Keto Sulfones to β-Hydroxy Sulfones with Alkyl Aluminum Compounds: Structure of Intermediate Hydroalumination Products

β-Hydroxy sulfones are important in organic synthesis. The simplest method of β-hydroxy sulfones synthesis is the hydrogenation of β-keto sulfones. Herein, we report the reducing properties of alkyl aluminum compounds R₃Al (R = Et, i-Bu, n-Bu, t-Bu and n-Hex); i-Bu₂AlH; Et₂AlCl and EtAlCl₂ in the hydrogenation of β-keto sulfones. The compounds i-Bu₂AlH, i-Bu₃Al and Et₃Al are the at best reducing agents of β-keto sulfones to β-hydroxy sulfones. In reactions of β-keto sulfones with aluminum trialkyls, hydroalumination products with β-hydroxy sulfone ligands [R₂AlOC(C₆H₅)CH₂S(O)₂(p-R¹C₆H₄]_n [where n = 1,2; 2aa: R = i-Bu, R¹ = CH₃; 2ab: R = i-Bu, R¹ = Cl; 2ba: R = Et, R¹ = CH₃; 2bb: R = Et, R¹ = Cl] and {[Et₂AlOC(C₆H₅)CH₂S(O)₂(p-ClC₆H₄]∙Et₃Al}_n 3bb were obtained. These complexes in the solid state have a dimeric structure, while in solutions, they appear as equilibrium monomer–dimer mixtures. The hydrolysis of both the isolated 2aa, 2ab, 2ba, 2bb and 3bb and the postreaction mixtures quantitatively leads to pure racemic β-hydroxy sulfones. Hydroalumination reaction of β-keto sulfones with alkyl aluminum compounds and subsequent hydrolysis of the complexes is a simple and very efficient method of β-hydroxy sulfones synthesis.     

Sulfamic Acid as a Cost‐Effective and Recyclable Catalyst for β‐Amino Carbonyl Compounds Synthesis

Sulfamic acid was used as a catalyst in the synthesis of β‐amino carbonyl compounds from amines, acetophenone and aldehyde. The reaction was carried out at room temperature. High selectivity, mild reaction temperature, cost‐effective catalyst, simple product separation and catalyst recycle were notable achievements in the reaction. Another feature was that the reaction could be performed on a relatively larger scale to the model reaction (50 times), which also gave good yields. In particular, the first preparation of β, β'‐diamino diketone derivatives via the direct coupling of amines, acetophenone and isophthalic aldehyde promoted by sulfamic acid has been developed.     

A Novel Approach to Synthesis of α，β－Unsaturated Ketones

A new approach to the synthesis of α，β-unsaturated ketones from 1,2,3-trimethyl benzimidazolium salt via the condensation reaction with aldehydes followed by the addition reaction of Grignard reagents with quaternary C=N bond was provided.     

A Novel Method for the Synthesis of α,β‐Unsaturated Amides Mediated by Samarium Diiodide

Promoted by Samarium diiodide (SmI₂), α,β‐unsaturated amides were formed from nitrogen anions (formed in situ by the reduction of nitro compounds) and α,β‐unsaturated esters. This reaction contrasts with the conjugate addition between amines and α,β‐unsaturated esters promoted by samarium triiodide (SmI₃) and provides an alternative attractive way to obtain α,β‐unsaturated amides using SmI₂.     

A Mild Isomerization Reaction for β,γ‐Unsaturated Ketone to α,β‐Unsaturated Ketone

A series of β,γ‐unsaturated ketones were isomerized to their corresponding α,β‐unsaturated ketones by the introduction of DABCO in iPrOH at room temperature. The endo‐cyclic double bond (β,γ‐position) on ketone was rearranged to exo‐cyclic double bond (α,β‐position) under the reaction conditions.     

Reductive Cyclodimerization of α, β‐ Unsaturated Ketones Promoted by AlCl3/Sm System: A Facile Synthesis of 2‐Aroyl‐1,3,4‐triaryl Cyclopentanol Derivatives

Promoted by AlCl₃/Sm bimetallic system, α, β‐unsaturated ketones underwent reductive cyclodimerization to afford cyclopentanol derivatives under mild conditions. The reaction is stereocontrolled and regioselective over the competitive carbon‐carbon double bond reduction.     

Synthesis of new optically active α,α′,β‐trisubstituted‐β‐lactones as monomers for stereoregular biopolyesters

Various optically active (4R)‐alkyloxycarbonyl‐3,3‐dialkyl‐2‐oxetanones as monomers were synthesized from L‐(S)‐malic acid in six steps to prepare a new family of stereopolyesters for biomedical applications. The synthesis began with an esterification followed of a dialkylation in the aim to introduce hydrophobic groups as methyl or reactive group as allyl. Then, a saponification has permitted to obtain the corresponding diacids that reacted with appropriate alcohols to furnish different monoesters. The last and most important step was activation of hydroxyl group of monoesters with the asymmetric carbon configuration inversion according to the Mitsunobu reaction. Thus, this reaction has provided lactones from monoesters with 100% enantiomeric excess which was confirmed by ¹H NMR and by the synthesis of corresponding isotactic and semicrystalline homopolyesters. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2586–2597     

Titanyl Acetylacetonate as an Efficient Catalyst for Regioselective 1,2‐Reduction of α,β‐Unsaturated Carbonyl Compounds and Conversion of α‐Diketones & Acyloins to Vicinal Diols with Sodium Borohydride

α,β‐Unsaturated aldehydes and ketones were reduced readily and exclusively to their corresponding allylic alcohols with NaBH₄ and catalytic amounts of titanyl acetylacetonate at room temperature. Reduction reactions were carried out in CH₃CN or THF. This reducing system was also efficient for the reduction of α‐diketones and acyloins to their corresponding vicinal diols in CH₃CN.     

Reduction of α,β unsaturated carbonyl compounds by Ni–BH4

The reduction of α,β unsaturated carbonyl compounds by sodiumborohydride is catalysed by Ni(bpy)Cl₂ (bpy=2,2′-bipyridine). Various carbonyl compounds having the general formula R₁CH=CHCRO [where R₁, R=C₆H₅, H; p-MeO---C₆H₄---,C₆H₄; p-CH₃---C₆H₄, C₆H₅; (m-OMe---)(p-OMe---)C₆H₃, C₆H₅; C₆H₅, (CH₃)₂CH---; CH₃, H; m-Br---C₆H₄---, C₆H₅] are reduced to corresponding allylicalcohol [R₁CH=CHCRHOH] at 25°C within half an hour. During these reductions the double bond is partially reduced to give saturated alcohols as minor products having the molecular formula R₁CH₂CH₂CRHOH. The reduction of trans-3-phenyl-2-propenal with NaBH₄ and catalytic amounts of Ni(bpy)Cl₂ in solvents containing active deuterium (D₂O, CD₃OD), leads to the partial incorporation of deuterium at the α and γ positions to give C---D bonded alcohols.     

Catalytic Asymmetric Intramolecular Homologation of Ketones with α‐Diazoesters: Synthesis of Cyclic α‐Aryl/Alkyl β‐Ketoesters

A catalytic asymmetric intramolecular homologation of simple ketones with α‐diazoesters was firstly accomplished with a chiral N,N′‐dioxide–Sc(OTf)₃ complex. This method provides an efficient access to chiral cyclic α‐aryl/alkyl β‐ketoesters containing an all‐carbon quaternary stereocenter. Under mild conditions, a variety of aryl‐ and alkyl‐substituted ketone groups reacted with α‐diazoester groups smoothly through an intramolecular addition/rearrangement process, producing the β‐ketoesters in high yield and enantiomeric excess.     

Synthesis of Conjugated α-D-Hexenopyranosiduloses

α-Enone sugars such as 2,3-dideoxy-α-D-hex-2-enopyranasid-4-uloses I and 3,4-dideoxy-α-D-hex-3-enopyranosid-2-uloses II involving the corresponding C-2 and C-4 methylated sugars 5, 10a and 10b were successfully synthesized from D-glucose in high yields by simple laboratory processes.     

Synthesis of α,β-unsaturated ketone from α-iodo ketone using photoirradiation

Irradiation of α-iodo ketone in hexane under a nitrogen atmosphere with a high-pressure mercury lamp (λ>300nm) at room temperature afforded the corresponding α,β-unsaturated ketones in good yield. This reaction affords a new, clean and convenient synthetic method for the α,β-unsaturated ketone.     

Photoinduced transformation of α,β-epoxyketones to β-hydroxyketones by Hantzsch 1,4-dihydropyridine

Irradiation (λ >300 nm) of Hantzsch 1,4-dihydropyridine with aromatic α,β-epoxyketones in acetonitrile selectively breaks the Cα---O bond of the epoxides giving the corresponding β-hydroxyketones in excellent yields.     

Novel and Efficient One Pot Condensation Reactions between Ketones and Aromatic Alcohols in the Presence of CrO3 Producing α,β‐Unsaturated Carbonyl Compounds

We report a new, effective and simple method for preparing α,β‐unsaturated carbonyl compounds by reacting ketones and aromatic alcohols at 56°C in the presence of CrO₃ (CrO₃ acts as an oxidant and also a catalyst) for around 10 h. The condensation reactions occurred effectively among a wide combination of ketones and alcohols. The procedure is simple and the yields can be high up to 98%. And a probable mechanism is proposed.     

Synthesis of α,β‐Unsaturated Ketones and Esters Using Polymer‐supported Selenium Bromide

Treatment of the polymer‐supported α‐phenylseleno ketones and esters prepared from polymer‐supported selenium bromide with ketone and ester enolates with hydrogen peroxide afford α,β‐unsaturated ketones and esters in good yields and high purities.     

Oxidative β‐Csp3−H Functionalization of tBuOH: A Selective Radical/Radical Cross‐Coupling Access to β‐Hydroxy Thioethers

An oxidative β‐Csp³?H functionalization of tert‐butanol (tBuOH) for the construction of C?S bonds through an iodine‐catalyzed Csp³?H/S?H coupling was successfully achieved. Different kinds of mercaptans were shown to be good coupling partners, affording the desired products in good yields. This protocol not only offers a novel method for the synthesis of β‐hydroxy thioethers, but also provides an effective strategy for selective radical/radical cross‐coupling.