Stereodefined Substituted Cyclopropyl Zinc Reagents from Gem-Bismetallics
摘要:
1,1- or n,n-Bismetallic reagents bearing a methoxymethyl ether in the gamma position undergo cyclization at room temperature to give monometalated, diastereoselectively substituted cyclopropanes, The nature of the substituents is crucial for this diastereoselection, a pi-chelation between one metal and a properly located unsaturation, as well as 1,2-strain, are proposed to explain the steric outcome of these reactions.
2-Bromo-3-trimethylsilylpropene. An annulating agent for five-membered carbo- and heterocycles
作者:Barry M. Trost、Brian P. Coppola
DOI:10.1021/ja00388a112
日期:1982.12
degradation product from any mechanism other than that proceeding directly through [3.3] shifts (e.g., 1 4 b 5 3b). The observed ratios in Table I are clearly incompatible with the generation of 3a, and hence 2 and/or 7, but show admirable coincidence with the values calculated for the direct sigmatropicshift sequence. These results constitute a truly surprising experimental manifestation of the theoretical
如果 2 是中间体(“[2 + 2 + 2]”),则 0:2:1 如果重排涉及 4 b 和 5(但不是 7)(“[3.3]”),并且 2:6:7 如果7 很容易获得(“spir0[3.3]”)。*~ 如果所有环碳上的标签以某种方式打乱(“随机”),该比例将为 1:10:7。检查未标记丁二酮的母峰包络 atm / e 86-8821 可以通过考虑 90% 13C 标记掺入和未富集位置中天然丰度标记的存在来预测上述选项的预期峰值比(表 I )。也许最明显的是,除了直接通过 [3.3] 转换(例如,1 4 b 5 3b)之外的任何机制形成双标记降解产物的必要性。表 I 中观察到的比率显然与 3a 的生成不相容,因此 2 和/或 7,但与为直接 sigmatropic 移位序列计算的值显示出令人钦佩的重合。这些结果构成了理论预测的真正令人惊讶的实验表现,即热 [2 + 2 + 21 炔烃环加成在动
TROST, B. M.;COPPOLA, B. P., J. AMER. CHEM. SOC., 1982, 104, N 24, 6879-6881
作者:TROST, B. M.、COPPOLA, B. P.
DOI:——
日期:——
MANDAI, TADAKATSU;NOKAMI, JUNZO;YANO, TORU;YOSHINAGA, YUKARI;OTERA, JUNZO, J. ORG. CHEM., 1984, 49, N 1, 172-174
Stereodefined Substituted Cyclopropyl Zinc Reagents from Gem-Bismetallics
作者:Dov Beruben、Ilane Marek、Jean F. Normant、Nicole Platzer
DOI:10.1021/jo00113a032
日期:1995.4
1,1- or n,n-Bismetallic reagents bearing a methoxymethyl ether in the gamma position undergo cyclization at room temperature to give monometalated, diastereoselectively substituted cyclopropanes, The nature of the substituents is crucial for this diastereoselection, a pi-chelation between one metal and a properly located unsaturation, as well as 1,2-strain, are proposed to explain the steric outcome of these reactions.
Facile one-pot synthesis of bromo homoallyl alcohols and 1,3-keto acetates via allyltin intermediates