The use of very electrophilic boranes RB(C(6)F(5))(2) widens the scope of the 1,1-carboboration reaction substantially. Simple terminal alkynes HC identical withCR undergo this reaction with the RB(C(6)F(5))(2) reagents rapidly under mild conditions to give high yields of very useful new alkenylborane products. Even internal alkynes RC identical withCR undergo 1,1-carboboration with the RB(C(6)F(5))(2)
R2Si(CC-SiMe3)2 [1a (Me), 1b (Ph)] with HB(C6F5)2 at low temperature (253 K (a), 273 K (b)) gives the –B(C6F5)2 substituted silacyclobutene products (4a,b) under kinetic control. Upon warming to room temperature they disappear to form the thermodynamically favoured isomeric silole derivatives (2a,b). Similar treatment of Me2Si(CC–R1)2 [5a (R1 = Ph), 5b (R1 = tert-butyl) with HB(C6F5)2 at room temperature
在低温下(253 K(a),273 K(b))用HB(C 6 F 5)2处理R 2 Si(C C-SiMe 3)2 [ 1a(Me),1b(Ph)]在动力学控制下–B(C 6 F 5)2取代的硅环丁烯产物(4a,b)。温热至室温后,它们消失以形成热力学上有利的异构硅烷衍生物(2a,b)。Me 2 Si(C C–R的相似处理1)2 [ 5a(R 1 = Ph),5b(R 1 =叔丁基)与HB(C 6 F 5)2在室温下得到稳定的–B(C 6 F 5)2取代的硅环丁烯衍生物6和分别为7。随后的光解作用导致这些产物中取代的环外C C双键从Z-到E-异构化。通过X射线晶体结构分析表征了硅杂环丁烯衍生物E - 6。