アリルとビニルハリドの過渡金属フリーボリレーションのための1,1-ビス[(ピナコラト) ボリルアルカネの化学選択結合:結合実験と理論的調査
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まとめ
この要約は機械生成です。新しい過渡金属のないボリレーション法では,1,1-bis[(pinacolato) ボリルアルカンを使用して,アリルおよびビニルハライドからオルガノボロナートエステルを生成する. この効率的なプロセスは,幅広い機能群の互換性とユニークな反応メカニズムを提供します.
科学分野
- 有機化学
- 有機金属化学
背景
- 移行金属触媒によるボリレーション反応は,オルガノボロナートエステルの合成に不可欠である.
- 既存の方法には高価で有毒な移行金属触媒が必要である.
- 金属のない代替品の開発は,持続可能な化学のために非常に望ましい.
研究 の 目的
- アリルとビニルハライドの新型移行金属フリーボリレーションプロトコルを開発する.
- 1,1-bis (ピナコラト) ボリルアルカンを効率的なボルン源として利用する.
- この新しいボリレーション反応のメカニズムを解明する.
主な方法
- 1,1-ビス (pinacolato) ボリルアルカンを使用したアリルおよびビニルハリドのボリレーション.
- 唯一の活性化剤として,サトリアム・テルト・ブトオキシードを使用する.
- 反応経路を理解するために実験的および理論的研究を行う.
主要な成果
- 多種多様なオーガノハリドの 移行金属無酸化を成功させた.
- 高い化学選択性と優れた機能的群耐性が観察されました.
- 主要な製品としてオルガノボロナートエステルの形成.
- 異常なルイス酸/塩基添加物の中間物質の特定
結論
- 新しい効率的で汎用的な過渡金属のないボリレーション法が確立されました.
- このプロトコルは従来の金属触媒によるボリレーションに 持続可能な代替手段を提供している.
- 機械的な洞察は,C-B結合形成のより深い理解を提供します.
関連する概念動画
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
Mechanism
The hydroboration-oxidation reaction is a two-step...
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
The observed...
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
Borane as a reagent is very reactive, as the...
Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
A...
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Thermodynamic Stability
Catalytic hydrogenation reactions help evaluate the relative thermodynamic stability of hydrocarbons. For example, the heat of hydrogenation of acetylene is −176 kJ/mol, and that of ethylene is −137 kJ/mol. The higher exothermicity associated...
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
The reaction is a two-step process. The mechanism is still under study, but for some reagent...