Cycloadditions in syntheses. VIII. Synthesis of 1,2-dihydrocyclobuta(c)-pyridine and -quinoline and their 3-substituted derivatives.

Abstract

1, 2-Dihydrocyclobuta [c] quinolin-3(4H)-one was synthesized from 4-methoxyquinolin-2(1H)-one according to our two-step procedure involving photoaddition of the latter to ethylene and subsequent elimination of methanol from the adduct. Chlorination of this compound with phosphoryl chloride afforded 3-chloro-1, 2-dihydrocyclobuta [c] quinoline. This 3-chloro derivative then afforded either the parent base (1, 2-dihydrocyclobuta [c]-quinoline) by reductive dechlorination, or a variety of 3-substituted derivatives by reaction with nucleophiles. In a similar manner, the corresponding 1, 2-dihydrocyclobuta [c] pyridine and its 3-substituted derivatives were synthesized from 1, 2-dihydrocyclobuta [c] pyridin-3(4H)-one obtained from 4-methoxy- or -acetoxy-pyridin-2(1H)-one and ethylene. Suitable reaction conditions for nucleophilic substitution reactions of the 3-chlorofunction were determined for each 1, 2-dihydrocyclobuta [c]-quinoline or -pyridine derivative.