Multicomponent Dipolar Cycloaddition Strategy: Combinatorial Synthesis of Novel Spiro-Tethered Pyrazolo[3,4-b]quinoline Hybrid Heterocycles.

The stereoselective syntheses of a library of novel spiro-tethered pyrazolo[3,4-b]quinoline-pyrrolidine/pyrrolothiazole/indolizine-oxindole/acenaphthene hybrid heterocycles have been achieved through the 1,3-dipolar cycloaddition of azomethine ylides generated in situ from α-amino acids and 1,2-diketones to dipolarophiles derived from pyrazolo[3,4-b]quinoline derivatives.

A facile tandem Michael addition/O-cyclization/elimination route to novel chromeno[3,2-c]pyridines.

A facile and efficient synthesis of a library of novel chromeno[3,2-c]pyridines has been achieved from the reaction of various 3,5-((E)-arylidene)-1-alkylpiperidin-4-ones and cyclic 1,3-diketones. The reaction presumably occurred via tandem Michael addition-intramolecular O-cyclization-elimination sequence in a single operation.

Ultrasound-assisted sequential multicomponent strategy for the combinatorial synthesis of novel coumarin hybrids.

The present investigation reports an easy access to a library of novel spiro-oxindole-pyrrolizine or pyrrolo[1,2-c]thiazole fused coumarin hybrid heterocycles through a one-pot sequential four-component reactions of 2,2-dimethyl-1,3-dioxane-4,6-dione, salicylaldehydes, isatins, and cyclic α-amino acids under ultrasound irradiation.