Nitrobenzenes substituted with electron-acceptor groups such as halogen, nitro, trifluoromethyl, pentafluorosulfanyl, or cyano underwent oxidative nucleophilic substitution with lithium salts of arylamines to afford N-aryl-2-nitroanilines.
(E)-N-trimethylsilyloxyenamines, easily accessible from aldonitrones, proved to be excellent nucleophiles in TMSOTf-induced diastereoselective aldol reaction, both with ketals and acetals, proceeding via an extended transition state and leading to a new aldol C-C-bond in the aldonitrone products, that can be readily hydrolysed to the corresponding aldehydes.
Three novel helical dications (helquats) containing phenanthridinium units have been synthesized from 6-(pyridin-2-ylethynyl)phenanthridine as a common precursor prepared by Sonogashira coupling of phenanthridin-6-yl triflate with 2-ethynylpyridine. Bisquaternization of the common precursor followed by rhodium-catalyzed [2+2+2] cycloisomerization led to the title helical dicationic scaffolds. The connectivity and spatial arrangement of the three target helquats were unambiguously established by X-ray crystal structure analysis.
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