Melen Rebecca L, Hansmann Max M, Lough Alan J, Hashmi A Stephen K, Stephan Douglas W
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6 (Canada).
Chemistry. 2013 Sep 2;19(36):11928-38. doi: 10.1002/chem.201301899. Epub 2013 Aug 6.
A series of propargyl amides were prepared and their reactions with the Lewis acidic compound B(C6F5)3 were investigated. These reactions were shown to afford novel heterocycles under mild conditions. The reaction of a variety of N-substituted propargyl amides with B(C6F5)3 led to an intramolecular oxo-boration cyclisation reaction, which afforded the 5-alkylidene-4,5-dihydrooxazolium borate species. Secondary propargyl amides gave oxazoles in B(C6F5)3 mediated (catalytic) cyclisation reactions. In the special case of disubstitution adjacent to the nitrogen atom, 1,1-carboboration is favoured as a result of the increased steric hindrance (1,3-allylic strain) in the 5-alkylidene-4,5-dihydrooxazolium borate species.
制备了一系列炔丙基酰胺，并研究了它们与路易斯酸性化合物B(C6F5)3的反应。结果表明，这些反应在温和条件下能生成新型杂环化合物。各种N-取代炔丙基酰胺与B(C6F5)3的反应会导致分子内氧硼化环化反应，生成5-亚烷基-4,5-二氢恶唑硼酸盐物种。仲炔丙基酰胺在B(C6F5)3介导的（催化）环化反应中生成恶唑。在氮原子相邻位置双取代的特殊情况下，由于5-亚烷基-4,5-二氢恶唑硼酸盐物种中空间位阻增加（1,3-烯丙基张力），有利于1,1-碳硼化反应。
