directed cyclization-dehydration cascade of α-aryloxy ketones and α-arylamino ketones was efficiently catalyzed by a cationic iridium-BINAP complex, which afforded various types of 4-substituted benzofurans and indoles in high yields with complete regioselectivity. The newly developed protocol also enabled the enantioselective preparation of chiral 4-acetyloxindole using a chiral iridium catalyst.
The Syntheses of Benzofuran-carboxylic Acids and the Acetylation of Their Esters
作者:Yoshiyuki Kawase、Matsuko Takashima
DOI:10.1246/bcsj.40.1224
日期:1967.5
Acetyl derivatives of 2, 3-dimethylbenzofuran and their methyl homologs were derived into the corresponding carboxylic acids by the haloform reaction, and the acetylation of thier esters by the Friedel-Crafts reaction was studied. The keto-esters obtained were hydrolyzed to give keto-acids, which were then further oxidized into dicarboxylic acids by the haloform reaction and decarboxylated to acetylbenzofurans
Cyclodehydration of various α-aryloxy ketones proceeded to give various multisubstituted benzofurans by using an Ir(III) catalyst, which was prepared from [Cp*IrCl2]2, AgSbF6, and Cu(OAc)2. The use of the cationic iridium complex with a carboxylate salt realized the efficient transformation at ambient temperature.