Oxidative Generation of 1-Nitroalkyl Radicals and Their Addition Reaction to Olefins
作者:Noriyoshi Arai、Koichi Narasaka
DOI:10.1246/bcsj.70.2525
日期:1997.10
1-Nitroalkyl radicals are generated by oxidation of potassium salt of 1-aci-nitroalkanes with ammonium hexanitratocerate(IV). When the oxidation is carried out in the presence of electron-rich olefins, such as silyl enol ethers, intermolecular addition of the radicals onto the olefins proceeds to afford β-nitro ketones, which are further converted to α,β-unsaturated ketones in high yield. Stereoselective
Access to 1,3-disubstituted cyclohexenes from zirconocenes containing a latent electrophilic allylic fragment is described. Requiring a specific conformation, 6-endo-trig cyclisation is based on the TMSOTf-mediated generation of a stabilized carbocation.
A chiral phosphoric acid catalyst enabled enantioselective 1,3-dioxane construction, useful for polyketide motif synthesis, via a hemiacetalization/intramolecular oxy-Michael addition cascade.
Phase-Transfer-Catalyzed Asymmetric Synthesis of Chiral<i>N</i>-Substituted Pyrazoles by Aza-Michael Reaction
作者:Su-Jeong Lee、Ju-Yeon Bae、Chang-Woo Cho
DOI:10.1002/ejoc.201500940
日期:2015.9
cinchona-based phase-transfer-catalyzed asymmetric aza-Michael reaction of pyrazole with various α,β-unsaturated ketones has been developed for the preparation of chiral N-substituted pyrazoles. This reaction provided the desired products in good yields (up to 99 %) with excellent enantioselectivities (87–94 % ee). In addition, the reaction of 3-methyl-1H-pyrazole, an unsymmetrically substituted pyrazole
K2CO3-Promoted oxy-Michael Addition/Cyclization of α,β-Unsaturated Carbonyl Compounds with Naphthols: Synthesis of Naphthopyrans
作者:Shan-Shan Li、Li-Li Zhao、Min Pan、Na Feng、Jin-Bao Peng、Ai-Jun Ma
DOI:10.3390/molecules28145502
日期:——
A potassium carbonate promoted tandem oxy-Michael addition/cyclization of α,β-unsaturated carbonyl compounds with naphthol derivatives for the synthesis of 2-substituted naphthopyrans was developed. Using the readily available, inexpensive potassium carbonate as the promoter, a range of different substitutednaphthopyrans were prepared.