Studies On Using Hypervalent Iodine (â…¢) Reagents To Synthesize Heterocyclic Compounds

This thesis consists of three parts. The first outlines the recent progress in the new synthetic pathways toward indole skeleton. The second and third parts deal with our studies on the synthesis of indole and imidazo[1,2-α]pyridines which feature the use of hypervalent iodine (Ⅲ) reagents.Our research includes:(1) Substituted anilines react with phenyliodonium ylides derived from 1,3-dicarbonyl compounds in-the presence of a catalytic amount of BF3·Et2O, producing 2-N-phenylamino-3-hydroxybut-2-enoate derivatives, which serve as precursors for the synthesis of substituted indoles. The indoles could be prepared directly from anilines and phenyliodonium ylides under both thermal and photochemical conditions. (2) Imidazo[1,2-α]pyridine-3-carboxylates can be prepared directly from 2-aminopyridines andβ-keto esters by using PhI(OAc)2 as oxidant and BF3·Et2O as catalyst. The amount of BF3·Et2O plays a key role in determining the reaction course. Using 0.2 equiv. of BF3·Et2O ensures the generation of imidazo[1,2-α]pyridines, while raising the amount of BF3·Et2O to 1.0 equiv. would result exclusively in the a-acetoxylation ofβ-keto esters.2-Aminopyridines can also react with 1,3-diones to afford 3-acylimidazo[1,2-α]pyridines.