10.1016/j.molstruc.2010.01.059
The research focuses on the 1,3-dipolar cycloaddition reaction of N-[4-nitrophenyl]-C-[2-furyl] nitrilimine with electron-rich dipolarophiles such as vinyl acetate, 2-propyne-1-ol, and styrene, aiming to synthesize specific pyrazole derivatives. The reaction's reactivity and regiochemistry were experimentally investigated and supported by theoretical DFT-based reactivity indexes using the B3LYP/6-31G(d) level of theory. The study employed a variety of analytical techniques including 1H and 13C NMR, IR spectroscopy, mass spectrometry, and elemental analysis to characterize the synthesized products. The regioselectivity of the reactions was further analyzed using DFT-based reactivity indexes, such as Fukui indexes, local softnesses, and local electrophilicity, to predict the favored interaction sites and elucidate the reaction mechanisms. The research successfully predicted the regiochemistry of the isolated cycloadducts and provided insights into the factors influencing the regioselectivity of these reactions.
10.1002/anie.201904520
The research focuses on the asymmetric synthesis of chiral 1,4-enynes through an organocatalytic alkenylation reaction between propargyl alcohols and trialkenylboroxines. The key strategy involves the acid-mediated generation of a carbocationic intermediate from propargyl alcohols, which then undergoes enantioselective alkenylation with trialkenylboroxines. A highly acidic chiral N-triflyl phosphoramide catalyst, featuring two distant Lewis basic oxygen atoms, was identified as crucial for achieving high reactivity and selectivity in the reaction. The study involved a series of experiments to optimize the reaction conditions, including catalyst and solvent screening, and the impact of substrate structure on yield and enantioselectivity. The researchers tested various propargyl alcohols and boroxines, and the results demonstrated the reaction's tolerance to different functional groups, leading to moderate to good yields and high enantioselectivities. The experiments utilized techniques such as 1H-NMR for yield determination and chiral HPLC methods for assessing enantiomeric excess. The research also explored the potential of the synthesized 1,4-enynes as synthetic intermediates for further functionalization, and proposed a catalytic cycle and transition state models to elucidate the reaction mechanism.
10.1016/j.tet.2008.10.111
The research investigates an efficient catalytic system for synthesizing a variety of α,β-unsaturated ketones using [(NHC)AuCl] (NHC stands for N-heterocyclic carbene) in the presence of a silver(I) salt. This system catalyzes the Meyer–Schuster rearrangement, converting easily accessible propargylic alcohols into α,β-unsaturated ketones with high yields. The catalysis is performed in a 2:1 mixture of methanol and water at 60°C, yielding good results even for tertiary alcohols and sterically demanding substrates. However, the system is unsuitable for terminal alkynes and primary alcohols, which produce low yields of target molecules due to unexpected by-products. Key chemicals involved in this research include propargylic alcohols as substrates, [(IPr)AuCl] as the preferred catalyst among tested gold–NHC complexes, and AgSbF6 as the silver salt. The study also explores the effects of various substituents on the aryl and acetylenic moieties of the substrates, revealing that electron-donating groups and tertiary alcohols generally afford excellent yields. Additionally, the research delves into mechanistic insights, proposing a pathway involving the activation of a water molecule by the gold complex rather than the traditional activation of the C≡C triple bond, and investigates the formation of furanone and indanone derivatives under these conditions.
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