アルケニルボロナートのイリジウム触媒によるエナチオセレクティブアリレーションのメカニズム的基礎
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PubMedで要約を見る
まとめ
この要約は機械生成です。イリジウム触媒は新しい3つの構成要素の結合反応を可能にします 精密なステレオ化学を持つ複雑な分子を形成します この方法はアルケニルボロンエステル,オーガノリチウム反応剤,およびアリル炭酸塩を効率的な合成に使用します.
科学分野
- 有機金属化学
- 非対称な触媒
- 合成有機化学
背景
- 有機化学では,ステレオ選択合成のための効率的な触媒方法の開発が不可欠である.
- 三要素結合反応は原子経済性を提供し,合成経路を簡素化します.
- イリジウム触媒は 複雑な分子構築の強力なツールとして 登場しました
研究 の 目的
- エナチオセレクティブとダイアステレオセレクティブの3つのコンポーネント結合反応を開発する.
- イリジウム触媒反応のメカニズムを調査する
- ステレオ選択性を制御する要因を理解する.
主な方法
- イリジウム ((phosphoramidite) コンプレクスを用いた触媒三要素結合.
- 運動分析と相対的立体化学の決定を含むメカニズム研究.
- 密度関数理論 (DFT) 計算とハメット研究
主要な成果
- この反応はアルケニルボロンエステル,オーガノリチウム反応剤,およびアルリル炭酸を高いステレオコントロールで成功的に結合する.
- 機械的調査は1,2-メタラートシフト経路を誘発したことを示した.
- DFTの計算と実験データは,ステリウムと電子因子によって制御されるステレオ選択性の付加とメタレートシフトの協調された性質を明らかにした.
結論
- 開発されたイリジウム触媒反応は,ステレオ化学的に豊富な化合物への新しい経路を提供します.
- この研究は,反応機構とステレオ選択性の決定因子に関する重要な洞察を提供します.
- この研究は,非対称合成におけるイリジウム触媒の有用性を拡大する.
関連する概念動画
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...
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...
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...
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
The observed regioselectivity can be explained based on the radical stability and steric effect. From the radical stability perspective, adding hydrogen bromide in the presence of peroxide directs the bromine radical at the less substituted carbon via a more stable tertiary radical intermediate. Similarly, in the steric framework, the...
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the...
In organic synthesis, the formation of products can be altered by changing the reaction conditions. For example, a dibromo addition product is formed when propene is treated with bromine at room temperature. In contrast, propene undergoes allylic substitution in non-polar solvents at high temperatures to give 3-bromopropene. In order to avoid the addition reaction, the bromine concentration must be kept as low as possible throughout the reaction. This can be achieved using N-bromosuccinimide...