ロジウム ((III)) 触媒によるボックイミンのアリレーションは,C-H結合機能化経由で行われます
Andy S Tsai1, Michael E Tauchert, Robert G Bergman
1Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.
Journal of the American Chemical Society
|January 6, 2011
まとめ
この研究は,C-H結合機能化を使用してイミンの最初のロジウム触媒アリレーションを導入します. この方法は,多様な機能群と互換性のあるアリル分岐のN-Boc-アミンを効率的に生成します.
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
- 合成方法論 合成方法論
背景:
- イミンは,汎用性の高い合成中間物質である.
- C-H機能化は,複雑な分子に原子経済的な経路を提供する.
- イミンの直接アリレーションは,合成的な課題であり続けている.
研究 の 目的:
- C-H結合機能化によるイミンの最初のロジウム触媒による直接アリレーションを開発する.
- この新しい合成変換の範囲と限界を探求する.
- 効率的なアリレーションのための重要な反応パラメータを特定する.
主な方法:
- ロジウム触媒はロジウムの触媒である.
- C-H アクティベーション/機能化
- 非調整ハリド抽出器の使用
- 反応最適化に関する研究
主要な成果:
- 直接のC-H機能化によるイミンのロジウム触媒によるアリレーションの成功.
- 主要な製品としてアリル分岐型N-Boc-アミンの形成.
- 幅広い機能グループ耐性の実証.
- 反応性にとって極めて重要な非調整ハリド抽出体の特定.
結論:
- イミンの直接アリレーションのための新しい効率的な方法が確立されました.
- このC-H機能化のアプローチは,価値あるアリル分岐アミンへのアクセスを提供します.
- この方法論は,複雑な分子合成のための大きな可能性を秘めている.
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.
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.
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.
Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN1
Treating arylamines with nitrous acid gives aryldiazonium salts that are effective substrates in nucleophilic aromatic substitution reactions. The diazonio group in these salts can be easily displaced by different nucleophiles, yielding a wide variety of substituted benzenes. The leaving group departs as nitrogen gas, and this easy elimination is the driving force for the substitution reaction.
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo, or cyano...
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo, or cyano...
α-Bromination of Carboxylic Acids: Hell–Volhard–Zelinski Reaction
The method to achieve α-brominated carboxylic acids using a mixture of phosphorus tribromide and bromine is known as the Hell–Volhard–Zelinski reaction. The reaction is catalyzed by phosphorus tribromide, which can be used directly or produced in situ from red phosphorus and bromine. The mechanism comprises PBr3 catalyzed conversion of acid to acid bromide and hydrogen bromide. The acid bromide enolizes to its enol form in the presence of HBr. The nucleophilic enol attacks the bromine molecule...
Electrophilic Addition to Alkynes: Hydrohalogenation
Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.


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