Tryptophan-derived tertiary amine-thiourea catalysts were shown to promote a cascade oxa-Michael–Michael reaction between ethylene β-keto esters and nitroolefins, resulting in the formation of 3,3-disubstituted 4-chromanones bearing a quaternary center in high diastereoselectivity and enantioselectivity. The chromanone products can be readily converted to biologically important fused and spiro tricyclic
色
氨酸衍生的叔胺-
硫脲催化剂可促进
乙烯β-
酮酯与硝基烯烃之间的级联oxa-Michael-Michael反应,导致形成具有高非对映选择性和四级中心的3,3-二取代的4-苯并二氢
呋喃酮。对映选择性。苯并二氢
吡喃酮产物可以容易地转化为
生物学上重要的稠合和螺
三环苯并二氢
吡喃。