Rhodium Fluoroapatite Catalyzed Conjugate Addition of Arylboronic Acids to α,β‐Unsaturated Carbonyl Compounds

Rhodium fluoroapatite (RhFAP) is an efficient catalyst for conjugate addition of organoboron reagents to α,β‐unsaturated carbonyl compounds. A variety of arylboronic acids and α,β‐unsaturated carbonyl compounds were converted to the corresponding conjugate‐addition products, demonstrating the versatility of the reaction. The reaction is highly selective. RhFAP was recovered quantitatively by simple filtration, and reused for four cycles.     

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).     

Conjugate Addition of Indoles to α, β-Unsaturated Ketones （Chalcones） Catalyzed by KHSO4 under Ultrasonic Conditions

Conjugate addition of indoles to a variety of α,β-unsaturated ketones （chalcones） mediated by a catalytic amount of KHSO4 at room temperature under ultrasonic conditions to afford the corresponding Michael adducts in good to excellent yields was reported.     

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.     

Nucleophilic Fluoroalkylation of α,β‐Unsaturated Carbonyl Compounds with α‐Fluorinated Sulfones: Investigation of the Reversibility of 1,2‐Additions and the Formation of 1,4‐Adducts

A detailed investigation of the reactions of PhSO₂CF₂H and PhSO₂CH₂F with (E)‐chalcone (=(E)‐1,3‐diphenylprop‐2‐en‐1‐one) at low temperatures revealed that these two reactions were kinetically controlled, and the ratios of 1,2‐ vs. 1,4‐adducts, which did not change much over time at these temperatures, reflect the relative rates of the two reaction pathways. The controlled experiments of converting the PhSO₂CF₂‐ and PhSO₂CHF‐substituted 1,2‐adducts to 1,4‐adducts showed that these isomerizations are not favored due to the low stability and hard‐soft nature of PhSO₂CF and PhSO₂CHF^? anions. Moreover, taking advantage of the remarkable stability and softness of (PhSO₂)₂CF^? anion, an efficient thermodynamically controlled isomerization of (PhSO₂)₂CF‐substituted 1,2‐adduct to 1,4‐adduct was achieved for the first time.     

Highly Enantioselective Iridium‐Catalyzed Hydrogenation of α,β‐Unsaturated Esters

α,β‐Unsaturated esters have been employed as substrates in iridium‐catalyzed asymmetric hydrogenation. Full conversions and good to excellent enantioselectivities (up to 99 % ee) were obtained for a broad range of substrates with both aromatic‐ and aliphatic substituents on the prochiral carbon. The hydrogenated products are highly useful as building blocks in the synthesis of a variety of natural products and pharmaceuticals.     

Toward the Synthesis of Modified Carbohydrates by Conjugate Addition of Propane‐1,3‐dithiol to α,β‐Unsaturated Ketones

Selected 5‐substituted derivatives 4 of 1,1‐diethoxy‐5‐hydroxypent‐3‐yn‐2‐one were treated with propane‐1,3‐dithiol under various conditions. The unprotected hydroxy ketones underwent cyclization during the dithiol addition and gave the corresponding 3‐(diethoxymethyl)‐2‐oxa‐6,10‐dithiaspiro[4.5]decan‐3‐ols 5 in 80–90% yield as the only products (Scheme 3 and Table 1). These products can be regarded as partly modified carbohydrates in the furanose form. When the benzyl‐protected analogues 10‐Bn of the 1,1‐diethoxy‐5‐hydroxypent‐3‐yn‐2‐one derivatives were treated with the same dithiol, however, no cyclization occurred; instead the corresponding 3‐{2‐[(benzyloxy)methyl]‐1,3‐dithian‐2‐yl}‐1,1‐diethoxypropan‐2‐one derivatives 11‐Bn were formed in good yield (up to 99%; Table 4). These 1,3‐dithianes were and are in the process of being converted to a number of new carbohydrate analogues, and here are reported high‐yield syntheses of functionalized molecules 17 belonging to the 5,5‐diethoxy‐1,4‐dihydroxypentan‐2‐one family of compounds (Table 7), via 15‐Bn (Table 5) and 16‐Bn (Table 6 and Scheme 8).     

Michael-Addition Reaction of Malononitrile with α,β-Unsaturated Cycloketones Catalyzed by KF／Al2O3

A series of KF/Al2O3 catalyzed Michael-addition reactions between malononitrile and α,β-unsaturated cycloketones in DMF solution were studied. At room temperature, 2-cyano-3-aryl-3-(1,2,3,4-tetrahydronaphthalen-1-one-2-yl) propionitrile derivatives were synthesized by the reaction between 2-arylmethylidene-1,2,3,4-tetra-hydronaphthalen-1-one and malononitrile. However, if the temperature was increased to 80℃, 2-amino-3-cyano-4-aryl-4H-benzo[h]chromene derivatives were obtained in high yields. When the α,β-unsaturated ketones were replaced by 2,6-biarylmethylidenecyclohexanone or 2,5-biarylmethylidenecyclopentanone, another series of 2-amino-3-cyano-4H-pyran derivatives was isolated successfully. The structures of the products were confirmed by X-ray diffraction analysis.     

Facile Preparation of Homoallyl β′，γ′—Unsaturated Amines via 1,2—Addition of α，β—Unsaturated Imines with Allylsamarium Bromide

A series of homoallyl β′，γ′-unsaturated amines were synthe sized via 1,2-addition of α，β-unsaturated imines with allylsamarium bromide in excellent yields under mild and neutral conditions.     

A Simple and Efficient Method for the Synthesis of α,β‐Unsaturated Acyl Azo Compounds with NaNO2‐Acetic Anhydride Under Mild Conditions

In this paper, eight aryl substituted α, β‐unsaturated acyl hydrazides undergo efficient oxidation to α,β‐unsaturated acyl azo compounds using NaNO₂‐acetic anhydride under mild conditions with excellent yields.     

Remote Sulfonamido Group Enhances Reactivity and Selectivity for Asymmetric Michael Addition of Nitroalkanes to α,β‐Unsaturated Aldehydes

The pyrrolidine–camphorsulfonamide‐based catalyst 1 a catalyzes the enantioselective conjugate addition of nitroalkanes to α,β‐unsaturated aldehydes in the presence of five equivalents of water in iPrOH to give the corresponding chiral Michael adducts in good yields and high enantioselectivities (up to 99 % ee) with a catalyst loading as low as 1 mol %.     

Studies on the Mass Spectra of N‐Aryl α,β‐Unsaturated γ‐Lactams

The mass spectra of a series of N‐aryl α,β‐unsaturated γ‐lactams were studied. Besides the molecular ion, the three characteristic fragments such as [M⁺‐29], [M⁺‐55], and [M⁺‐82] were commonly found in a series of N‐Aryl α,β‐unsaturated γ‐lactams in EI/MS. Further more the mechanism for the interpretation of these fragments is also de scribed.     

Iridium‐Catalyzed Enantioselective Allylic Substitution of Unstabilized Enolates Derived from α,β‐Unsaturated Ketones

We report Ir‐catalyzed, enantioselective allylic substitution reactions of unstabilized silyl enolates derived from α,β‐unsaturated ketones. Asymmetric allylic substitution of a variety of allylic carbonates with silyl enolates gave allylated products in 62–94 % yield with 90–98 % ee and >20:1 branched‐to‐linear selectivity. The synthetic utility of this method was illustrated by the short synthesis of an anticancer agent, TEI‐9826.     

KF-蒙脱土催化下丙二腈与α,β-不饱和酮的迈克尔加成反应

本论文研究了KF-蒙脱土催化下丙二腈与α,β-不饱和酮的迈克尔加成反应,研究发现在不同的反应温度下可以得到加成和环化两种不同的产物。该方法和现有的方法相比具有产率高、反应条件温和、操作简单、试剂易得等优点。