5-Alkenyl-2-methoxy-2-cyclopentenones, readily available from thermolysis of 2-alkenylcyclopropylcarbene-chromium complexes, can be converted to nine-membered rings by treatment with vinylcerium reagents and subsequent anionic oxy-Cope rearrangement.
                                    可以容易地从2-烯基环丙基卡宾-
铬络合物的热解获得的5-烯基-2-甲氧基-
2-环戊烯酮,可以通过用
乙烯基铈试剂处理和随后的阴离子氧基-Cope重排而转化为九元环。