General procedure for the synthesis of 3
To a reaction tube equipped with a stir bar were addedN -(quinolin-8-yl)benzamide (1a , 50 mg, 0.2 mmol),
2-diazo-1H -indene-1,3(2H )-dione (2 , 52 mg, 0.3
mmol), Co(acac)2 (10 mg, 0.04 mmol),
Ag2CO3 (165 mg, 0.6 mmol) and ethyl
acetate (1.5 mL). The tube was then sealed, and the mixture was stirred
at 100 °C (metal module heating) under air for 15 h. Upon completion, it
was cooled to room temperature, filtered through a pad of celite, and
concentrated under reduced pressure. The residue was purified by silica
gel column chromatography using petroleum ether/ethyl acetate (3:1) as
eluent to afford 3a . Other products 3b -3twere obtained in a similar manner.