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終端アルケンのPt触媒によるエナチオセレクティブ二酸化にはB2 ((pin) 2) が含まれる
Laura T Kliman1, Scott N Mlynarski, James P Morken
1Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
Journal of the American Chemical Society
|August 26, 2009
まとめ
アルケンのプラチナ触媒によるエナチオセレクティブボリレーションにより,キラル二酸化物が生成されます. この効率的な方法は,低触媒負荷を使用し,多用途の製品形成経路を提供します.
科学分野:
- 有機金属化学 有機金属化学
- アシンメトリック・カタリシス
- 合成有機化学 合成有機化学について
背景:
- チラルの1,2-および1,4-ダイオールは,有機合成における貴重な構成要素である.
- これらの非対称合成のための効率的な触媒方法の開発は,依然として重要な課題です.
- プラチナ触媒は,C-B結合形成のためのユニークな反応性を提供します.
研究 の 目的:
- 単純な単位置換アルケンのプラチナ触媒による新種のエナチオセレクティブボリレーションを記述する.
- この変換における容易に入手可能なキラル・フォスフォニート・リガンドの有用性を調査する.
- アルケンの前駆体からキラル1,2および1,4ダイオルの合成を実証する.
主な方法:
- プラチナで触媒化された末端アルケーンにビスコランディボロンをエナチオ選択的に添加する.
- 立体化学的制御のためにキラル・フォスフォニート・リガンドを使用した.
- 触媒の負荷は1モル%のプラチナであった.
- 続いて,中間の1,2-bis (((ボロナート) エステルをキラル1,2-ジオールに酸化する.
- 介在物質のホモロゲーション/酸化により,キラル1,4-ジオール.
主要な成果:
- 様々な単位置換アルケンのPt触媒によるエナチオセレクティブボリレーションが成功しました.
- 低触媒負荷 (1 mol % Pt) で高効率が観察されました.
- 同じ中間物質からキラル1,2-ジオールとキラル1,4-ジオールの両方の合成が実証されました.
結論:
- アルケンからキラルダイオルのエナチオセレクティブ合成のための新しい,効率的なPt-触媒化された方法が開発されました.
- この方法論は,1,2-および1,4-ダイオール構造の両方へのアクセスを提供して,汎用的です.
- 低触媒負荷と容易に入手可能なリガンドの使用は,このアプローチを合成アプリケーションに魅力的にします.
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.
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
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.
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.
01:25Radical Anti-Markovnikov Addition to Alkenes: Overview
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
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.
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.