N-Propargylic β-Enaminones: Common Intermediates for the Synthesis of Polysubstituted Pyrroles and Pyridines
摘要:
N-Propargylic beta-enaminones have been used as common intermediates for the synthesis of polysubstituted pyrroles and pyridines. Best results have been obtained using DMSO as solvent. In the presence of CS(2)CO(3) N-propargylic beta-enaminones are cyclized to pyrroles in good to high yields, whereas omitting bases and using CuBr leads to the selective formation of pyridines.
N-Substituted formamides as nucleophiles react with in situ-generated 1,4-oxazepines from N-propargylic β-enaminones followed by spontaneous N-deformylation to deliver densely substituted 2-aminopyridines in good yields (31–88%). The formyl group is found to be a superior traceless activating group of free amines and would ultimately be removed in situ. This reaction proceeds smoothly at room temperature
A new strategy for the synthesis of pyridines from <i>N</i>-propargylic β-enaminothiones
作者:Yilmaz Kelgokmen、Metin Zora
DOI:10.1039/c8ob03180k
日期:——
A newmethod for the synthesis of 2,4,5-trisubstituted pyridines from N-propargylic β-enaminothiones is reported. β-Enaminothiones were prepared by thionation of the corresponding β-enaminones with Lawesson's reagent. When treated with diisopropylamine in DMF at room temperature, N-propargylic β-enaminothiones yielded 2,4,5-trisubstituted pyridines in moderate to high yields, along with small amounts
Base-promoted ring-closing carbonyl–allene metathesis for the synthesis of 2,4-disubstituted pyrroles
作者:Guolin Cheng、Weiwei Lv、Lulu Xue
DOI:10.1039/c8gc01675e
日期:——
A base-promoted ring-closing carbonyl–allene metathesis reaction of N-allenyl β-enaminones (generated in situ from N-propargyl β-enaminones) gives 2,4-disubstituted pyrroles with cleavage of the C(sp)–C(sp3) bond. This transition metal-free procedure generates 1 equiv. of acetic acid as the sole byproduct. A preliminary mechanistic study supports a stepwise [2 + 2] cycloaddition/retro [2 + 2] reaction