三次性ボロンエステルのプロトデボロネーション:三次性アルキルステレオジェニックセンターの非対称合成
Stefan Nave1, Ravindra P Sonawane, Tim G Elford
1School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
Journal of the American Chemical Society
|November 18, 2010
まとめ
現在では,セシウムフッ化物またはテトラブチラモニウムフッ化物三水素を用いて,三次性ボロンエステルを効率的にプロトデボロン化することができる. この方法はステレオ化学的構成を保ち,キラルアルカンにデウテリウムラベルを付けることができます.
科学分野:
- 有機化学 オーガニック・ケミストリー
- 合成方法論 合成方法論
- ステレオセレクティブ合成
背景:
- 三次ボランは,カルボキシル酸によって容易にプロトボロン化されます.
- 三次性ボロンエステルには,効率的なプロトデボロネーション方法がない.
- 新しい合成経路の開発は,複雑な分子にアクセスするために不可欠です.
研究 の 目的:
- 三次性ボロンエステルの効率的なプロトデボロネーション方法を開発する.
- キラル三次性ボロンエステルのステレオレテンティブプロトデボロネーションを達成するために.
- デウテリウムラベル付キラルアルカンの合成を可能にするために.
主な方法:
- セシウムフッ化物 (CsF) と水を使用して,三次性ボロンエステルのプロトデボロン化.
- テトラブチラモニウムフッ素三水素 (TBAF·3H2O) を使用したプロトデボロネーション.
- デウテリウムラベルにデウテリウム酸化物 (D2O) を利用する.
主要な成果:
- 三次性ボロンエステルの高効率のプロトボロン化が達成されました.
- プロトデボロネーション中に観察された構成の必須の完全な保持.
- デウテリウムラベル付エンアンチオ濃縮三次アルケンの合成が成功しました.
- (S) - ターメロンの合成への応用.
結論:
- 三次ボロンエステルの新しく,効率的で,ステレオレテンティブなプロトデボロネーション方法を開発した.
- この方法により,価値あるデュテリウムラベル付キラルアルカンにアクセスできます.
- 自然製品合成におけるこの方法の有用性を実証しました.
さらに関連する動画
関連する概念動画
02:36Regioselectivity 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.
03:08Hydroboration-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.
01:29Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.
02:47Alkynes 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.
01:14Alkylation of β-Diester Enolates: Malonic Ester Synthesis
Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.
02:15Preparation of Alcohols via Addition Reactions
Overview
The acid-catalyzed addition of water to the double bond of alkenes is a large-scale industrial method used to synthesize low-molecular-weight alcohols. An acidic atmosphere is required to allow the hydrogen in the water molecule to act as an electrophile and attack the double bond in an alkene. The addition of a proton to the double bond creates a carbocation intermediate. The proton preferentially bonds to the less substituted end of the double bond to create a more stable carbocation...
The acid-catalyzed addition of water to the double bond of alkenes is a large-scale industrial method used to synthesize low-molecular-weight alcohols. An acidic atmosphere is required to allow the hydrogen in the water molecule to act as an electrophile and attack the double bond in an alkene. The addition of a proton to the double bond creates a carbocation intermediate. The proton preferentially bonds to the less substituted end of the double bond to create a more stable carbocation...