Pseudoesters and derivatives. XXIII Reaction of 3-bromo-5-methoxyfuran-2(5 [formula omitted])-one with nucleophiles. Formation of cyclopropane derivatives

Abstract

The reactions of 3-bromo-5-methoxyfuran-2 (5 H )-one ( 1 ) with nucleophiles in acetonitrile, in the presence of potassium carbonate and tetrabutylammonium bromide as a catalyst, are reported. The bromofuranone 1 reacts, with several carbon and oxygen nucleophiles to give the cyclopropane bis-lactones 7 , 8 , 11 or 12 . When 1 is reacted with diethylamine or propane-2-thiol in a 2:1 ratio, similar cyclopropane bis-lactones 16 or 21 , respectively, are formed. This behaviour is explained on the basis of a mechanism involving a double Michael addition, followed by ring closure via internal nucleophilic substitution of the halogen.