Mechanistic Analysis for Sigma-Participation Based on Silicon Effects

基于硅效应的西格玛参与机理分析

• 批准号: 01470025
• 负责人: SHIMIZU Nobujirou
• 金额: $ 4.1万
• 依托单位: Kyshu University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1989
• 资助国家: 日本
• 起止时间: 1989 至 1990
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-01470025/
• 关键词: sigma-Participation; Carbocation Stability; Hyperconjugation; Solvolysis; beta-Silicon Effect; シグマ関与機構; βーケイ素効果; 炭素陽イオン; シグマ共役; βケイ素効果

Kinetics and products have been investigated in detail for the solvolysis of alpha- or beta-silyl-substituted benzylic derivatives, i. e., alpha- (pentamethyldisilanyl) benzyl halides (1), 2, 2, 3, 3-tetramethy1-2, 3-disila-1-indanyl chloride (2), 2, 2-dimethy1-2-sila-1-indanyl halides (3), 1-pheny1-2-(trimethylsily) ethyl trifluroacetate (4), 2-phenyl-1- (pentamethyldisilanyl) cyclopropyl bromide (5), and 2-phenyl-2- (trimethylsilyl) ethyl trifluroacetate (6), and other related derivatives. The following observations are instructive. (1) alpha-Silicon destabilizes the benzylic cation by 3-4 kacal/mol relative to carbon ; (2) alpha- (Disilanyl) benzyl cation and alpha- (trimethylsilylmethyl) -benzyl cation are respectively 6.2-6.8 and 7.2 kcal/mol more stable than the corresponding alpha- (trialkylsilyl) benzyl cation and alpha-alkylbenzyl cation ; (3) 1 solvolyzes via kc mechanism despite a marked rate acceleration by the beta-silyl group and a rearrangement of this group seemingly characteristic of sigma-participation ; (4) The alpha-disilanyl compound 2 in which the Si-Si bond is orthogonal to the leaving group exhibits no beta-silicon effect indicative of hyperconjugative origin for the betasillic on effect ; (5) In sigma-participated (4) or aryl-paticipated solvolysis (5), the presence of the beta-silicon allows the kc solvolysis to occur exclusively or competitively.

已经详细研究了α-或β-甲硅烷基取代的苄基衍生物的溶剂解作用的动力学和产物，即。例如，α-(五甲基二硅烷基)苄基卤 (1), 2, 2, 3, 3-四甲基1-2, 3-disila-1-茚满基氯 (2), 2, 2-二甲基1-2-sila-1-茚满基卤化物(3)、1-苯基1-2-(三甲基甲硅烷基)三氟乙酸乙酯(4)、 2-苯基-1-（五甲基二硅烷基）环丙基溴（5）和2-苯基-2-（三甲基甲硅烷基）三氟乙酸乙酯（6）以及其他相关衍生物。以下观察结果具有启发性。 (1) 相对于碳，α-硅使苯甲基阳离子不稳定3-4 kacal/mol； (2) α-(二硅烷基)苄基阳离子和α-(三甲基甲硅烷基甲基)-苄基阳离子分别比相应的α-(三烷基甲硅烷基)苄基阳离子和α-烷基苄基阳离子稳定6.2-6.8和7.2kcal/mol； (3)尽管β-甲硅烷基团显着加速了速率，并且该基团的重排似乎具有西格玛参与的特征，但1仍通过kc机制进行溶剂分解； (4)其中Si-Si键与离去基团正交的α-二硅烷基化合物2不表现出表明β硅酸效应的超共轭起源的β-硅效应； (5) 在西格玛参与的 (4) 或芳基参与的溶剂分解 (5) 中，β-硅的存在使得 kc 溶剂分解能够排他地或竞争性地发生。

项目成果

N.Shimizu 他2名: "Effect of SiーSi αBonds on Stability of Adiacent Benzylic Cations." Chem.Lett.1937-1940 (1990)

N.Shimizu 和其他 2 人：“Si-Si αBonds 对邻接苯甲基阳离子稳定性的影响。Chem.Lett.1937-1940 (1990)

N.Shimzu 他4名: "Silicon Effects.III.Rates and Products for Solysis of αー(PentamethyLaisilanyl) benzyl Halides and 2,2,3,3ーTetramethy1ー2,3ーdisilaー1ーindany1 Chloride." Bull.Chem.Soc.Jpn.

N.Shimzu 和其他 4 人：“硅效应。III. α-（五甲基赖硅烷基）苄基卤化物和 2,2,3,3-四甲基 1-2,3-二硅基-1-茚满基氯化物的溶解速率和产品。” .Chem.Soc.Jpn。

N. Shimizu et al.: "Silicon Effects. III. Rates and Products for Solvolysis of alpha-(Pentamethyldisilanyl) benzyl Halides and 2, 2, 3, 3-Tetramethy1-2, 3-disila-1-indanyl Chloride. Structure and Stability of alpha-(Pentamethyldisilanyl benzyl Cation in S

N. Shimizu 等人：“硅效应。III. α-（五甲基二硅烷基）苄基卤化物和 2, 2, 3, 3-四甲基 1-2, 3-disila-1-茚满基氯的溶剂分解速率和产物。结构和

N. Shimizu et al.: "Rates and Mechanism for the Solvolysis of 2, 2-Dimethyl 2-sila-1-indanyl Bromide and alpha-Trialkylsilylbenzyl rho-Toluenesulfonates. alpha-Silicon Effect on the Stability of Benzylic Cations." Bull. Chem. Soc. Jpn.64. (1991)

N. Shimizu 等人：“2, 2-二甲基 2-sila-1-茚满基溴和 α-三烷基甲硅烷基苄基对甲苯磺酸盐的溶剂分解速率和机制。α-硅对苄基阳离子稳定性的影响。”

N.Shimizu: "Solvolysis of 2-pentamethyldishldisilanylbenzyl Halides and 2,2,3,3-Tetramethy1-2,3-disila-1-indanyl Chloride." J.Am.Chem.Soc.

N.Shimizu：“2-五甲基二硅烷基苯甲基卤化物和 2,2,3,3-四甲基 1-2,3-二硅基-1-茚满基氯的溶剂分解。”