Highly Chemo‐, Enantio‐, and Regioselective Synthesis of α,α‐Disubstituted Furanones by Cu‐Catalyzed Conjugate Addition

A highly chemo‐, enantio‐, and regioselective synthesis of furanones bearing an α,α‐disubstituted quaternary stereogenic center is reported. The Cu‐catalyzed enantioselective conjugate addition of organoaluminum reagents to unsaturated ketoesters at room temperature and subsequent lactonization took place. Synthetic transformations of furanones represent facile approaches to various cyclic or acyclic compounds bearing a quaternary stereogenic center.     

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。     

Nickel‐Catalyzed α‐Carbonylalkylarylation of Vinylarenes: Expedient Access to γ,γ‐Diarylcarbonyl and Aryltetralone Derivatives

We report a Ni‐catalyzed regioselective α‐carbonylalkylarylation of vinylarenes with α‐halocarbonyl compounds and arylzinc reagents. The reaction works with primary, secondary, and tertiary α‐halocarbonyl molecules, and electronically varied arylzinc reagents. The reaction generates γ,γ‐diarylcarbonyl derivatives with α‐secondary, tertiary, and quaternary carbon centers. The products can be readily converted to aryltetralones, including a precursor to Zoloft, an antidepressant drug.     

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).     

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.     

Rhodium‐Catalyzed Chemo‐, Regio‐, and Enantioselective Addition of 2‐Pyridones to Terminal Allenes

A rhodium‐catalyzed chemo‐, regio‐, and enantioselective addition of 2‐pyridones to terminal allenes to give branched N‐allyl 2‐pyridones is reported. Preliminary mechanistic studies support the hypothesis that the reaction was initiated from the more acidic 2‐hydroxypyridine form, and the initial kinetic O‐allylation product was finally converted into the thermodynamically more stable N‐allyl 2‐pyridones.     

Access to Cyclic β‐Amino Acids by Amine‐Catalyzed Enantioselective Addition of the γ‐Carbon Atoms of α,β‐Unsaturated Imines to Enals

Disclosed herein is a new catalytic approach for an efficient access to cyclic β‐amino acids widely found in bioactive small molecules and peptidic foldamers. Our method involves addition of the remote γ‐carbon atoms of α,β‐unsaturated imines to enals by iminium organic catalysis. This highly chemo‐ and stereo‐selective reaction affords cyclic β‐amino aldehydes that can be converted to amino acids bearing quaternary stereocenters with exceptional optical purities. Our study demonstrates the unique power of organic catalytic remote carbon reactions in rapid synthesis of functional molecules.     

Carbon Magnetic Resonance Spectra of α, β, γ, δ- and α, β, α′, β′- Unsaturated Ketones

Carbon-13 spectra of a series of 26 unsaturated ketones (ortho- and para-cyclo-hexadienones and corresponding open-chain analogues) have been measured by Fourier-transform. Pulse spectroscopy. A complete analysis has been achieved by means of double resonance experiments using noise-modulated and coherent off-resonance proton irradiation and with the aid of non-decoupled spectra. Chemical shifts are interpreted in terms of charge distribution in the dienone system and of methyl substituent effects. Carbon chemical shifts were also obtained for O-protonated ortho- and para-cyclohexadienones. One-bond and long-range carbon-proton and carbon-fluorine spin coupling constants are reported for several compounds.     

Stereoretentive Addition of N‐tert‐Butylsulfonyl‐α‐Amido Silanes to Aldehydes,Ketones, α,β‐Unsaturated Esters,and Imines

Enantioenriched N‐tert‐butylsulfonyl‐α‐amido silanes were successfully reacted with aldehydes, ketones, imines, and α,β‐unsaturated esters in the presence of a sub‐stoichiometric amount of CsF (0.5 equiv) in 1,2‐dimethoxyethane (DME) at ?20 °C to afford the corresponding coupling products with up to 89 % enantiospecificity in a retentive manner.     

Microwave‐Assisted Convenient Synthesis of α,β‐Unsaturated Esters and Ketones via Aldol‐Adduct Elimination

Various fluorinated 3‐oxo ester/1,3‐diketones were reacted with carbonyl compounds, in presence of piperidine and under microwave irradiation, to afford (E)‐α,β‐unsaturated esters and ketones in good yields. The systematic study reveals that the reaction proceeded through the formation of aldol adduct. The method provides a new and simple way for C,C bond formations.