Thermal fragmentation of 2-azidobenzo[b]thiophene in the presence of alkenes: a new synthetic route to 1-(2-benzo[b]thienyl)aziridines and/or thiochroman-4-carbonitriles
作者:Piero Spagnolo、Paolo Zanirato
DOI:10.1039/p19880003375
日期:——
Mild thermalfragmentation of 2-azidobenzo[b]thiophene in the presence of olefins results in the formation of 1-(2-benzo[b]thienyl)aziridines and/or 4-cyanothiochromans in fairly good yields. The formation of aziridines, at the expense of thiochromans, is favoured by electron-poor olefins and by a decrease in the reaction temperature. Evidence is presented in favour of a singlet nitrene intermediate
在烯烃存在下2-叠氮基苯并[ b ]噻吩的温和热裂解导致形成1-(2-苯并[ b ]噻吩基)氮丙啶和/或4-氰基噻吩并以相当好的收率形成。贫电子的烯烃和反应温度的降低有利于以硫代色烷为代价形成氮丙啶。提供了有利于单线态氮烯中间体的证据,该中间体加成到烯烃双键上或经历开环反应以得到被存在的烯烃所俘获的邻-喹啉类亚乙基硫酮。这些发现提供了第一个由2-nitreno取代的噻吩开环的例子。
Polar cycloaddition of 1-benzothiopyrylium salts with conjugated dienes and some transformations of the cycloadducts
cycloadduct 4hA with a variety of bases affords the spirocyclopentene derivative 7 and the spiro-1,2-dioxolane derivative 8. A mechanism involving a biradical intermediate is discussed for the formation of the above products 7 and 8 on the basis of chemical evidence. Reduction of the cycloadduct 4hA with sodium borohydride or sodium cyanoborohydride is also described.
1-苯并硫代吡啶鎓盐2与共轭二烯的极性环加成反应在区域和立体上特异性地进行,从而以良好的产率得到相应的苯并稠合的双环sulf盐4。环加合物4与亲核试剂如甲醇或水的反应导致开环,分别得到2-(丁-2-烯基)-和2-(丁-3-烯基)-取代的2 H -1-苯并噻喃5和6。 。用多种碱处理环加合物4hA,得到螺环戊烯衍生物7和螺-1,2-二氧戊环衍生物8。讨论了涉及双自由基中间体的机理,用于基于化学方法形成上述产物7和8。证据。还描述了用硼氢化钠或氰基硼氢化钠还原环加合物4hA。
A novel synthesis of α,β-unsaturated nitriles from aromatic ketones via cyanophosphates
Reaction of aromaticketones with diethyl phosphorocyanidate in the presence of lithium cyanide gave cyanophosphates, which were converted into α,β-unsaturated nitriles by treatment with boron trifluoride etherate in high yields.