Iodide-promoted aldiminium ion-alkyne cyclizations. A convenient synthesis of substituted tetrahydropyridines and 3-alkylidenepiperidines.
作者:Larry E. Overman、Achintya K. Sarkar
DOI:10.1016/s0040-4039(00)74663-6
日期:1992.7
Iodide-promotedcyclizations of aldehydes with 4-alkynylamines and 3-alkynylamines provide direct synthetic access to alkylidenepiperidines 4 and tetrahydropyridines 8, respectively.
Silver(I) carboxylate complexes promote the carboxylative cyclization of allenylmethylamines to afford 5-alkenyl-1,3-oxazolidin-2-ones in 2-propanol. The use of an N-heterocyclic carbene ligand (IPr) under pressurized CO2 is effective in suppressing the intramolecular hydroamination that leads to 2,5-dihydropyrroles. The mechanism involving a nucleophilic attack of the carbamate of the allene moiety and a subsequent protonation was realized on the basis of experimental and theoretical results involving a model intermediate, the alkenylgold(I) complex, which was synthesized from Au(OH)(IPr) and 1-methylamino-2,3-butadiene.