アルキルエレクトロフィルの鉄触媒によるボリル化
Thomas C Atack1, Rachel M Lecker, Silas P Cook
1Department of Chemistry, Indiana University , 800 East Kirkwood Avenue, Bloomington, Indiana 47405-7102, United States.
Journal of the American Chemical Society
|June 24, 2014
まとめ
この研究では,鉄(III) アセトアセテートとテトラメチルエチレンダイアミンを用いてアルキルハリドを直接ボリル化するための費用対効果の高い方法を導入しています. このプロセスは,様々なハリドを温和な条件下で有価なボロナートに効率的に変換します.
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
- オルガノボロン化学 オルガノボロン化学
背景:
- アルキルハリドの直接的ボリル化が,オルガンボロン化合物の合成に不可欠である.
- 既存の方法は,しばしば高価な触媒や厳しい条件を必要とする.
- より軽く,よりアクセシブルなボリレーション技術の開発は,継続的な課題です.
研究 の 目的:
- アルキルハリドとビス・ピナコラト・ディボロンの直接クロスカップリングのための低コストで効率的な方法を開発する.
- 非活性化およびステリック阻害アルキルハリドを含む,直接ボリレーションに適した基板の範囲を拡大する.
- 堅牢で軽度の反応プロトコルを確立するために.
主な方法:
- 鉄 (III) アセトアセテート (Fe (acac) 3) を触媒前駆体として利用する.
- テトラメチルエチレンダイアミン (TMEDA) をリガンドとして使用する.
- 様々なアルキルハリド (第一,二次,三次ブロミド,ベンジル/アリル塩化物,トシラート,メシラート) をビス・ピナコラート・ディボロンと反応させる.
- 温和な室温条件下で反応を起こす.
主要な成果:
- 活性化および非活性化された一次,二次,三次アルキルブロミドの直接ボリル化が成功しました.
- ベンジルまたはアリル塩化物,トシラート,およびメシラートのボリル化が実証されています.
- この反応は,幅広い機能群の互換性と強度を示している.
結論:
- 開発されたFe ((acac) 3 / TMEDAシステムは,アルキルハリドボリレーションのための実用的で経済的経路を提供します.
- この方法は,温和でユーザーフレンドリーな条件下でオルガノボロナートへのアクセスのための多用途のツールを提供します.
- 広範囲の基質の範囲と堅固さは,このアプローチを合成有機化学にとって非常に価値のあるものにします.
関連する概念動画
03:08Hydroboration-Oxidation of Alkenes
9.9K
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.
9.9K
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
19.7K
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.
19.7K
02:36Regioselectivity and Stereochemistry of Hydroboration
7.7K
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...
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...
7.7K
01:10α-Alkylation of Ketones via Enolate Ions
2.3K
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...
2.3K
02:38Electrophilic Addition to Alkynes: Halogenation
7.3K
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
7.3K
02:15Preparation of Alcohols via Addition Reactions
5.7K
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...
5.7K