Intramolecular [2 + 2]cycloadditions of dialkylketenes with alkenes. Regiochemistry of intramolecular [2+2]cycloadditions of ketenes with alkenes
作者:Barry B. Snider、Alban J. Allentoff、Marleen B. Walner
DOI:10.1016/s0040-4020(01)81460-5
日期:——
Unsaturated dialkylketenes 7a, 7b and 7c undergo intramolecular [2 + 2]cycloadditions to give 8a (45%), 9b (23%) and 9c (45%). Intramolecular cycloadditions of dialkylketenes give higher yields than intramolecular cycloadditions of monoalkylketenes, even though dialkylketenes are less reactive than monoalkylketenes. An intramolecular competition experiment with ketene 17 establishes that trans-alkenes
不饱和二烷基烯酮7a,7b和7c经历分子内[2 + 2]环加成,得到8a(45%),9b(23%)和9c(45%)。即使二烷基烯酮的反应性不如单烷基烯酮,二烷基烯酮的分子内环加成比单烷基烯酮的分子内环加成具有更高的产率。乙烯酮17的分子内竞争实验确定,在分子内环加成中,反式烯烃的反应性比顺式烯烃高约33倍。酮36提供预期的双环[3.2.0]庚酮37中的22%和28%的双环[3.1.1]庚酮38。