一般的な銅-BINAP触媒によるケトンの非対称プロパルギルプロパルギルボロナートによるプロパルギルボロナートによるプロパルギルプロパルギルプロパルギルプロパルギルプロパルギルプロパルギルプロパルギルプロパルギルプロパルギル
Keith R Fandrick1, Daniel R Fandrick, Jonathan T Reeves
1Chemical Development, Boehringer Ingelheim Pharmaceuticals Inc., 900 Ridgebury Road/P.O. Box 368, Ridgefield, Connecticut 06877-0368, USA. keith.fandrick@boehringer-ingelheim.com
Journal of the American Chemical Society
|June 7, 2011
まとめ
新しい銅-BINAP触媒は,ケトンの高度にエナチオセレクティブなプロパルギレーションを可能にします. この多用途な方法により,ホモプロパルギル添加物,すなわち様々な有価な有機化合物を合成するための有用な前駆物質が生成されます.
科学分野:
- 有機化学 オーガニック・ケミストリー
- カタリシス カタリシス カタリシス
- アシンメトリック・シンセシス
背景:
- エナチオセレクティブ合成は,医薬品と微細化学品にとって極めて重要です.
- 炭素-炭素結合形成のための効率的な触媒システムの開発は,依然として重要な課題です.
研究 の 目的:
- ケトンプロパルギレーションのための操作的にシンプルで高度にエナチオセレクティブな方法を開発する.
- 生成されたホモプロパルギル添加物の基質の範囲と合成的有用性を調査する.
主な方法:
- 銅-BINAPは,プロキラルケトンのエナチオセレクティブプロパルギレーションを触媒化した.
- メチルエチルケトンをモデル基板として利用した.
- 得られたアダクトの他の機能群への変換を研究した.
主要な成果:
- 様々なプロキラルケトンのプロパルギュレーションにおいて高いエナチオセレクティビティを達成した.
- 方法の適用性を幅広い基板に実証した.
- ホモプロパルギルアダクトを γ-ブチロラクトン,β-ヒドロキシメチルケトン,β-ヒドロキシカルボキシラートに成功裏に変換した.
結論:
- 開発された銅-BINAP触媒反応は,ホモプロパルギル添加物への直接的で高度にエナチオセレクティブな経路を提供します.
- これらのアダクトは,価値ある有機分子の合成のための多用途な中間物質として機能します.
- この方法論は,複雑な有機構造の非対称合成のためのツールキットを拡張します.
関連する概念動画
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
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.
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.
Hydroboration-Oxidation of Alkenes
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.
α-Alkylation of Ketones via Enolate Ions
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 strong interaction...
Regioselectivity and Stereochemistry of Hydroboration
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.
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.
Reactions of Aldehydes and Ketones: Baeyer–Villiger Oxidation
Baeyer–Villiger oxidation converts aldehydes to carboxylic acids and ketones to esters. The reaction uses peroxy acids or peracids and is often catalyzed by acid. The reaction is named after its pioneers, Adolf von Baeyer and Victor Villiger. The reaction is achieved by a wide range of peracids such as m-chloroperoxybenzoic acid (mCPBA), perbenzoic acid (C6H5COOOH), peracetic acid (CH3COOOH), hydrogen peroxide (H2O2), and tert-butyl hydroperoxide (t-BuOOH).
The carbonyl center is activated by...
The carbonyl center is activated by...
Base-Promoted α-Halogenation of Aldehydes and Ketones
α-Halogenation of aldehydes and ketones is a reaction involving the substitution of α hydrogens with halogens in the presence of a base. The reaction begins with the abstraction of α hydrogen by the base to produce a nucleophilic enolate ion. This intermediate undergoes a subsequent nucleophilic substitution with the halogen to produce a monohalogenated carbonyl compound. If the starting substrate has more than one α hydrogen, it is difficult to stop the reaction at the stage of...


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