Synthesis and Cyclization of 1-(2-Hydroxyphenyl)-2-propen-1-one Epoxides: 3-Hydroxychromanones and -flavanones versus 2-(1-Hydroxyalkyl)-3-coumaranones
摘要:
Competitive alpha and beta cyclization of 2'-hydroxychalcone epoxides affords 2-(alpha-hydroxybenzyl)-3-coumaranone and/or 3-hydroxyflavanones, which depends on the conditions employed. Epoxidation of 2'-hydroxychalcones by dimethyldioxirane followed by either base- or acid-catalyzed ring closure provides a novel, general, and efficient method for the synthesis of trans-3-hydroxyflavanones, which includes also the naturally occurring derivatives. Extension of this two-step procedure to 1-(2-hydroxyphenyl)-2-alken-1-ones was also accomplished. A strong preference for alpha cyclization was observed in the case of beta-unsubstituted or -monoalkylated alpha,beta-enones, while both 2,2-dimethyl-3-hydroxychromanones and 2-(1-hydroxy-1-methylethyl)-3-coumaranones were obtained from the beta,beta-dimethylated substrates.
A convenient and general synthesis of trans-3-hydroxyflavanones from chalcones by dimethyldioxirane epoxidation and subsequent base-catalyzed cyclization
作者:Tamás Patonay、Gábor Tóth、Waldemar Adam
DOI:10.1016/s0040-4039(00)60674-3
日期:1993.8
2'-Hydroxychalcone epoxides were found to give trans-3-hydroxyflavanone and 2-(alpha-hydroxybenzyl)-3-coumaranone under basic conditions. Epoxidation of 2'-hydroxychalcones with dimethyldioxirane followed by treatment of tetrabutylammonium hydroxide provides a convenient and general method for the synthesis of trans-3-hydroxyflavanones.
Synthesis and Cyclization of 1-(2-Hydroxyphenyl)-2-propen-1-one Epoxides: 3-Hydroxychromanones and -flavanones <i>versus</i> 2-(1-Hydroxyalkyl)-3-coumaranones
作者:Tamás Patonay、Albert Lévai、Csaba Nemes、Tibor Timár、Gábor Tóth、Waldemar Adam
DOI:10.1021/jo960163z
日期:1996.1.1
Competitive alpha and beta cyclization of 2'-hydroxychalcone epoxides affords 2-(alpha-hydroxybenzyl)-3-coumaranone and/or 3-hydroxyflavanones, which depends on the conditions employed. Epoxidation of 2'-hydroxychalcones by dimethyldioxirane followed by either base- or acid-catalyzed ring closure provides a novel, general, and efficient method for the synthesis of trans-3-hydroxyflavanones, which includes also the naturally occurring derivatives. Extension of this two-step procedure to 1-(2-hydroxyphenyl)-2-alken-1-ones was also accomplished. A strong preference for alpha cyclization was observed in the case of beta-unsubstituted or -monoalkylated alpha,beta-enones, while both 2,2-dimethyl-3-hydroxychromanones and 2-(1-hydroxy-1-methylethyl)-3-coumaranones were obtained from the beta,beta-dimethylated substrates.