Study On The Synthesis Of Aromatic-fused Pyran Compounds Catalyzed By Lewis Acids

Aromatic-fused pyran is an important structural unit in many biologically active compounds.The Lewis acid-catalyzed synthesis of aromatic-fused pyran compounds was studied in this thesis,which is composed with two parts as follows:1.The transformation of 2-hydroxy chalcone to cyclopenta[c]chromene can be efficiently catalyzed by cationic lanthanide complexes[Ln?CH₃CN?₉]³⁺[?AlCl₄?₃]^3–·CH₃CN in the presence of naphthalene-2-thiol.[Yb?CH₃CN?₉]³⁺[?AlCl₄?₃]^3–·CH₃CN shows the highest catalytic activity in this transformation among the cationic lanthanide complexes screened and naphthalene-2-thiol is a key factor affecting the yields of cyclopenta[c]chromenes.2.The transformation of naphthyl 3-methylcrotonate to 2,3-dihydro-benzo[f]chromen-1-one can be efficiently catalyzed by ferric chloride.A series of aromatic-fused pyrone were obtained in moderate to high yields.A two-step mechanism involving Fries rearrangement and intramolecular hydroalkoxylation is proposed.