Synthesis of 7-hydroxy-6,7-dihydro-indole and 6 ',7 '-dihydro-3,7 '-biindole derivatives from domino reactions of arylglyoxals or methyl ketones with enamines

摘要

A series of interesting 7-hydroxy-2-aryl-6,7-dihydro-indol-4(5H)-ones 3 was successfully synthesized in moderate to good yields by the domino reactions of different arylglyoxals 1 with enamines 2 under catalyst-free conditions. 7-Hydroxy-2-aryl-6,7-dihydro-indol-4(5H)-ones 3 could also be prepared in moderate yields by the iodine-promoted one pot-two step reactions of methyl ketones 6 with enamines 2. The reaction of 3a with N-methyl indole 7a in the presence of PTSA afforded 2'-aryl-6',7'-dihydro[3,7'-biindol]-4'(5'H)-ones 8a in 81% yield. In addition, 3,7'-bis-indoles 8 could also be observed in 47-73% yields by one pot domino reaction of arylglyoxals 1 with enamines 2 and indoles 7 over two steps. This protocol provides a simple and practical method to construct diverse 7-hydroxy-6,7-dihydro-indole derivatives 3 and 3,7'-bis-indoles 8 from easily obtained starting materials.