A novel synthesis of 2‐vinyldihydropyrans and dihydro‐1,4‐oxazines (morpholine derivatives) from alkynals and alkynones has been developed. The cyclizations require a mild generation of catalytic ruthenium carbenes from terminal alkynes and (trimethylsilyl)diazomethane followed by trapping with carbonyl nucleophiles. Mechanistic aspects of the new cyclizations are discussed.
                                    已经开发了由
炔烃和炔酮合成2-
乙烯基二氢
吡喃和二氢-1,4-恶嗪(吗啉衍
生物)的新方法。环化需要从末端
炔烃和(三甲基甲
硅烷基)
重氮甲烷中轻度生成催化
钌碳烯,然后用羰基亲核试剂捕集。讨论了新环化的机械方面。