Synthesis of chromones and 4-hydroxyquinolines based on uncatalyzed condensations of 1-methoxy-1,3-bis(trimethylsilyloxy)-1,3-butadiene with 2-alkoxy- and 2-nitrobenzoyl chlorides and related reactions.

The reaction of 1-methoxy-1,3-bis(trimethylsilyloxy)-1,3-butadiene with 2-methoxybenzoyl chlorides afforded 3,5-diketoesters which were transformed, by treatment with boron tribromide, into functionalized 2-hydroxychroman-4-ones or chromones. The reaction of 1-methoxy-1,3-bis(trimethylsilyloxy)-1,3-butadiene with 2-nitrobenzoyl chlorides and subsequent reduction of the nitro group afforded functionalized 4-hydroxyquinolines. Their tautomeric equilibrium was studied by NMR spectroscopy and by computational methods.