Ketenimines pyridines

DCC, and l-methyl-2-chloropyridinium iodide (Mulcaiyama s reagent). Analogously, amides can be dehydrated with P2O5, pyridine, and AI2O3 to give ketenimines ... 

Poe et al. [ 109] have measured the rate of formation of ketenimine ylide 20 in the presence of traps of singlet C6F5N such as dimethylsulfide. Laser flash photolysis of pentafluorophenyl azide in the presence of various amounts of dimethylsulfide (a scavenger of singlet pentafluoro phenyl nitrene), at a fixed concentration of pyridine, lowers the yield of ylide 20, but does not increase the rate of formation of the ylide. This demonstrates that dimethylsulfide reacts with a precursor of ylide 20 (singlet pentafluorophenyl nitrene) but not the immediate precursor of the ylid (perfluorodehydroazepine). This result... 

Condensation of 2-azido-P-phenethylamine with 4-chloro- or 4-nitrobenzaldehyde followed by reaction with diphenylketene in refluxing toluene gives the ketenimine 59 which undergoes an intramolecular [2tc + 27t] cyclisation to the azeto[2,l-6][l,3]benzodiazepines 60 <97T13449>. The method may be used also to synthesise azeto[2,l- )]quinazolines, the main thrust of the publication, but the tether cannot be increased further as the respective 8- and 9-membered ring systems could not be formed. UV irradiation of 4,6-diazido-3-methylisoxazolo[4,5-c]pyridine gives two products which have been identified and isoxazolo-... 

Reactions of dinucleophiles with biselectrophiles Reversal of regiospecificity Pyridines from ketenimines... 

Phosphorus pentoxide pyridine Ketenimines from carboxylic acid amides... 

The cycloaddition reaction of the ketenimines (101) with the in situ formed 1-azadienes (105) afforded pyridines or pyrimidines (106a-b) depending on their substitution pattern. Ketimines (101) were obtained from the three-component, one pot reaction of nitriles (98), acid chlorides (99) and phosphites (100) while 1-azadienes (105) were formed from the Nef isocyanide/Perkov reaction sequence involving aldehydes (102), nitriles (103) and dimethyl methylphosphonate (104) (Scheme 26). ... 

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