Borabenzene Derivatives. 24.<sup>1</sup> From Lithium 1-Methylboratabenzene to 2-Mono- and 2,2-Disubstituted 1-Methyl-1,2-dihydroborinines with Me<sub>3</sub>Si, Me<sub>3</sub>Ge, Me<sub>3</sub>Sn, and Me<sub>3</sub>Pb Substituents. Degenerate Sigmatropic Rearrangements with Exceptionally Low Barriers and the Structure of 2-(Me<sub>3</sub>Sn)C<sub>5</sub>H<sub>5</sub>BMe
作者:Gerhard E. Herberich、Jörg Rosenplänter、Bernd Schmidt、Ulli Englert
DOI:10.1021/om9605701
日期:1997.3.1
ΔH⧧ = 43.3(6) kJ mol-1, and ΔS⧧ = −52(2) J K-1 mol-1; for 3 ΔG300⧧ = 43.4(9) kJ mol-1, ΔH⧧ = 27.8(3) kJ mol-1, and ΔS⧧ = −52(2) J K-1 mol-1] and are lower than those found for previously investigated systems. The Sn and Pb satellites observed for 4 and 5 in THF solutions are quenched by catalytic amounts of DMSO while chemical shifts are not affected even at higher concentrations. The Si compound 2
Li(C 5 H 5 BMe)(1)与亲电子体Me 3 ECl(E = Si,Ge,Sn,Pb)的反应生成1,2-二氢硼烷酮2-(Me 3 E)C 5 H 5 BMe(2 − 5)。Sn化合物4的结构显示出延长的Sn-C(环)键[228.7(2)pm]。在溶液中的化合物2 - 5是fluxional并显示[1,3]所述的Meσ迁移迁移3从C-2] E组至C-6。通过NMR光谱已经确定了2和3的简并σ重排的障碍[对于2 Δ ģ 300 ⧧ = 58.9(11)千焦摩尔-1,Δ ħ ⧧ = 43.3(6)千焦摩尔-1,Δ小号⧧ = -52(2)JK -1摩尔-1 ; 为3 Δ ģ 300 ⧧ = 43.4(9)千焦摩尔-1,Δ ħ ⧧ = 27.8(3)千焦摩尔-1,Δ小号⧧ = -52(2)JK -1摩尔-1 ],并且低于为先前研究的系统找到的那些。在4和5观测到的Sn和Pb卫星通过催化量的