1,1-Carboboration of Dialkynyltin Compounds using Triorganoboranes of Greatly Different Lewis Acid Strength. 1,4-Stannabora-cyclohexa-2,5-dienes and Characterization of Zwitterionic Intermediates†
1,1-Carboboration of Dialkynyltin Compounds using Triorganoboranes of Greatly Different Lewis Acid Strength. 1,4-Stannabora-cyclohexa-2,5-dienes and Characterization of Zwitterionic Intermediates†
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DOI：
10.1002/zaac.201300007
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发表时间：
2013-06
期刊：
影响因子：
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通讯作者：
B. Wrackmeyer;P. Thoma;S. Marx;G. Glatz;R. Kempe
中科院分区：
文献类型：
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作者：
B. Wrackmeyer;P. Thoma;S. Marx;G. Glatz;R. Kempe
抽象的。比较了三有机硼烷Br3、Et-9-BBN、BPh3和B(C6F5)3与不同的二烷基(二有机)锡化合物(R12Sn(C≡C-R2)2，R12=-(CH2)5-，R2=H(A)，r1=nBu，r2=H(B)，r1=Ph，r2=H(C)，r1=r2=nBu(D))的反应性。1，1-碳硼化很容易发生在两个连续的步骤(分子间和分子内)，导致锡烯或1，4-锡硼环己-2，5-二烯或其混合物。最弱的Lewis-酸性三有机硼烷BEt3和Et-9-BBN选择性地与二乙炔基锡化合物形成锡，而强亲电性的B(C6F5)3选择性地生成1，4-锡-环己烷-2，5-二烯。在某些情况下，可以用多核磁共振波谱(1H、11B、13C和119Sn核磁共振)检测到两性离子中间体，并且可以用X射线结晶学确定这种中间体的分子结构以及最终产物1，4-锡-环己二烯-2，5-二烯的结构。
Abstract. Triorganoboranes BR3, Et-9-BBN, BPh3, and B(C6F5)3, were compared in their reactivity towards various dialkynyl(diorgano)tin compounds (R12Sn(C≡C–R2)2 with R12 = –(CH2)5–, R2 = H (a), R1 = nBu, R2 = H (b), R1 = Ph, R2 = H (c), R1 = R2 = nBu (d)). 1,1-Carboboration took place readily in two consecutive steps (inter- and intramolecular), leading either to stannoles or to 1,4-stannabora-cyclohexa-2,5-dienes, or mixtures thereof. The weakest Lewis-acidic triorganoboranes BEt3 and Et-9-BBN afford selectively stannoles with diethynyltin compounds, whereas the strongly electrophilic B(C6F5)3 leads selectively to 1,4-stannabora-cyclohexa-2,5-dienes for all dialkynyltin compounds studied. In several cases, zwitterionic intermediates could be detected by multinuclear magnetic resonance spectroscopy (1H, 11B, 13C, and 119Sn NMR), and the molecular structure of such an intermediate as well as that of the final product, an 1,4-stannabora-cyclohexa-2,5-diene, could be determined by X-ray crystallography.