Concise Synthesis of α-Substituted 2-Benzofuranmethamines and Other 2-Subsituted Benzofurans via α-Substituted 2-Benzofuranmethyl Carbocation Intermediates
作者:Nikhom Wongsa、Ubonta Sommart、Thunwadee Ritthiwigrom、Arife Yazici、Somdej Kanokmedhakul、Kwanjai Kanokmedhakul、Anthony C. Willis、Stephen G. Pyne
DOI:10.1021/jo302554v
日期:2013.2.1
Propargyl amines 4, where R3 is aryl, undergo 5-exo-dig cyclization reactions under relatively mild conditions (AgNO3, DMF, 60 °C, 1 h) to give 3-amino-2,3-dihydro-2-arylmethylidenebenzofurans 5 (R3 = aryl). In contrast, substrates where R3 is alkyl undergo competing 6-endo-dig and 5-exo-dig cyclization processes. The hydroxymethyl substrate 4 (R3 = CH2OH), however, was smoothly converted to its corresponding