1a and 2a, decomposition was observed whereas the reaction of the other tetraynes with Et3B affords siloles, 1,6-dihydro-1,6-disilapentalenes, 1,6-dihydro-1,6-stannasilapentalenes, and tricyclic heterocycles. In several cases it proved possible to show the stepwise proceeding of the intramolecular 1,1-vinylboration, once the reaction had started with an intermolecular 1,1-ethylboration. Zwitterionic
四炔R 1 CC–SiMe 2 –CC–SiMe 2 –CC⋯SiMe 2 –CCR 2 [R 1 = R 2 = H(1a),SnMe 3(1b),R 1 = SiMe 3,R 2 = H(2a),R 2 = SnMe 3(2b)]和R 1 CC–SiMe 2 –CC–SnMe 2 –CC–SiMe 2 –CCR 1 [R 1 = H(3a),n Bu(3b)),制备了t Bu(3c),i Pent(3d),Ph(3e),SiMe 3(3f)],并研究了它们对三乙基
硼烷Et 3 B 4的反应性。在1a和2a的情况下,观察到分解,而其他四炔与Et 3的反应B提供甲
硅烷基,1,6-二氢-1,6-二
硅戊
戊烯,1,6-二氢-1,6-
锡那拉
戊烯和
三环杂环。在几种情况下,一旦反应以分子间的1,1-
乙基硼化开始,证明分子内的1,
1-乙烯基
硼化的逐步进行是可能的。在3与Et 3 B反应的