Regioselective ring-opening cyclization of cyclohexane-1,3-dione-2-spirocyclopropanes with stabilized sulfonium ylides provided 2,3-trans-disubstituted 2,3,4,6,7,8-hexahydro-5H-1-benzopyran-5-ones in high yields without the formation of any isomers. The obtained product was readily converted into highly substituted chromane.
                                    环己烷-1,3-二酮-2-螺
环丙烷与稳定的
硫鎓烷基化物的区域选择性开环环化提供了2,3-反式-二取代的2,3,4,6,7,8-六氢-5 H -1-苯并
吡喃-高产率的5-ones,不形成任何异构体。所获得的产物易于转化为高度取代的苯并二氢
吡喃。