Cannizzaro reaction of 2-chloro-3-formylquinolines and its synthetic utility for 2-acetylfuro[2,3-b]quinolines: The alkaloid analogues

Cannizzaro reaction of 2-chloro-3-formylquinolines was investigated under two different conditions. Under both conditions, redox and methoxylation proceeded simultaneously and gave 2-methoxy-3-formylquinolines, 2-methoxyquinolin-3-yl-methanols and 2-methoxyquinoline-3-carboxylic acids. The synthesized 2-methoxy-3-formylquinolines were then condensed with acetone in the presence of sulphuric acid to give 4-(2-methoxy-quinolin-3-yl)-but-3-en-2-ones which in turn were bromocyclized and dehydrobrominated to get 2-acetylfuro[2,3- b ]quinolines. Graphical Abstract We have synthesized 2-methoxy-3-formylquinolines from 2-chloro-3-formylquinolines under Cannizzaro reaction conditions. In this reaction, besides the redox reaction, substitution (methoxylation) also proceeded to afford three products. By optimising the conditions we have isolated 2-methoxy-3-formylquinolines as major products. The 2-methoxy-3-formylquinolines were condensed with acetone and then bromocyclised to give 2-acietylfuro[2,3- b ]quinolines.