Zn(OTf)2-catalyzed cyclization of proparyl alcohols with anilines, phenols, and amides for synthesis of indoles, benzofurans, and oxazoles through different annulation mechanisms.
Zn(OTf)2 (10 mol %) catalyzed the cyclization of propargyl alcohols with PhXH (X = O, NH) in hot toluene (100 degrees C) without additive and gave indole and benzofuran products with different structures. In such transformations, alpha-carbonyl intermediates A and C were isolated as reaction intermediates. The 1,2-nitrogen shift in the formation of indole is catalyzed by Zn(OTf)2, and its mechanism has been elucidated. This catalytic cyclization is also applicable to the synthesis of oxazoles through the cyclization of propargyl alcohols and amides without a 1,2-nitrogen shift.
Kumar
Manyam Praveen
MP
Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan 30043.
Liu
Rai-Shung
RS
D000438:Alcohols / Q000737:chemistry*; D000577:Amides / Q000737:chemistry; D000814:Aniline Compounds / Q000737:chemistry; D001572:Benzofurans / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D003500:Cyclization; D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry; D008698:Mesylates / Q000737:chemistry*; D015394:Molecular Structure; D010080:Oxazoles / Q000138:chemical synthesis* / Q000737:chemistry; D010636:Phenols / Q000737:chemistry; D013237:Stereoisomerism
D000438:Alcohols; D000577:Amides; D000814:Aniline Compounds; D001572:Benzofurans; D007211:Indoles; D008698:Mesylates; D010080:Oxazoles; D010636:Phenols; C012077:trifluoromethanesulfonic acid; C023650:aniline