Mono-deoxygenation of Nitroalkanes, Nitrones, and Heterocyclic N-Oxides by Hexamethyldisilane through 1,2-Elimination: Concept of “Counterattack Reagent”
摘要:
Transformation of secondary nitroalkanes to ketoximes was achieved in 40-73% yields by treatment of the corresponding nitronate anions with hexamethyldisilane. In this new mono-deoxygenation process, hexamethyldisilane acted as a "counterattack reagent". The conversion of nitrones to imines was also achieved in 82-88% yields by use of trimethylsilyllithium. Similarly, heterocyclic N-oxides were converted to the corresponding N-heterocycles in 73-86% yields. These deoxygenation processes presumably involve a 1,2-elimination.
The development of photoredox reactions of 1,3-dipolarcycloaddition of nitrones with alkenes is reported. It offers an efficient synthetic method to obtain isoxazolidine derivatives under mild conditions in synthetically useful yields. The nitrones are cyclized with oxidizable styrenes and aliphatic alkenes via a polar radical crossover cycloaddition reaction through photocatalytic reaction without
Rh(III)-Catalyzed C–H Cyclization of Arylnitrones with Diazo Compounds: Access to 3-Carboxylate Substituted<i>N</i>-Hydroxyindoles
作者:Yazhou Li、Jian Li、Xiaowei Wu、Yu Zhou、Hong Liu
DOI:10.1021/acs.joc.7b01393
日期:2017.9.1
Recently, N-hydroxyindole derivatives have received much interest because of their unique structural motif and various biological activities. In this study, we report the first example of a Rh(III)-catalyzed reaction of arylnitrones with α-diazoketoesters or α-diazodiketones to produce N-hydroxyindole derivatives. Intriguingly, we could build the N-hydroxyindole scaffold by blocking the cleavage of
Catalytic Asymmetric 1,3‐Dipolar Cycloaddition of β‐Fluoroalkylated α,β‐Unsaturated 2‐Pyridylsulfones with Nitrones for Chiral Fluoroalkylated Isoxazolidines and γ‐Amino Alcohols
across various aromatic and aliphatic nitrones in the presence of a chiral NiII/bis(oxazoline) catalyst. The process was tuned by 4 Å molecular sieves, chiralbis(oxazoline) ligands, reaction solvents, and temperature. A wide array of optically pure fluoroalkylated isoxazolidines were obtained, thus facilitating the asymmetric synthesis of an enantioenriched α‐trifluoromethylated γ‐amino alcohol in gram‐scale
arylnitrones and diazo compounds by C–H activation/[4 + 1] annulation with a C(N2)–C(acyl) bond cleavage is reported, and 2,3-disubstituted NH indoles are directly synthesized in up to a 94% yield. A variety of functional groups are applicable to this reaction to give the corresponding products with high selectivity. Compared to other previously reported Rh(III)-catalyzed synthesis of homologous series, this method
A series of novel enantiomerically pure spiro-isoxazolidines and spiro-isoxazolines were synthesized regioselectively by 1,3-dipolarcycloadditionusing respectively two dipoles, nitrones and nitrileoxides, on the exocyclic double bond of the B ring of tomentosin (α-methylene-γ-butyrolactone), a sesquiterpene lactone extracted from Dittrichia viscosa.