Regiospecific Michael reaction of (+)-euryfuran with activated 1,4-benzoquinones

(+)-Euryfuran cycloadds regiospecifically to activated monosubstituted 1,4-benzoquinones under mild conditions to give the corresponding Michael adducts which, depending on the quinone substituent, undergo in situ redox reactions to the respective euryfurylbenzoquinones. One of the reported Michael adducts undergoes a facile stereoselective cyclisation under oxidant conditions to afford a naphthofuro[4,3-c]benzopyran derivative. The regiospecificity of the Michael and cyclisation reactions are discussed.