ボロンアミディナートとCO2,CO,その他の小分子との反応
Meghan A Dureen1, Douglas W Stephan
1Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.
Journal of the American Chemical Society
|September 3, 2010
まとめ
ピアスのボランは,カルボジミドと反応して,ボロンアミディナートを形成する. これらの化合物は,CO2,CO,およびニトリルなどの基板との多様な挿入反応を経験し,その反応性を示しています.
科学分野:
- オルガノボロン化学 オルガノボロン化学
- メイングループ 化学
- 合成有機化学 合成有機化学について
背景:
- ボロンアミジナートは,触媒と材料科学における潜在的な応用を持つ化合物のクラスです.
- ボロンアミジナートの反応性を理解することは,新しい合成方法論の開発に不可欠です.
- ピアーズボラン (HB(C6F5) 2) は,オーガノボロン化学でよく知られている反応剤です.
研究 の 目的:
- ピアスのボランとカルボディイミドの反応を調査する.
- 得られたボロンアミディネートによる挿入反応化学を調査する.
- これらの新しいボロン化合物の構造および反応性特性を解明する.
主な方法:
- ピアスのボランとテルトブチルまたはイソプロピルカルボジミドの反応によるボロンアミディナートの合成.
- スペクトロスコーピック技術 (NMRなど) を用いた製品の特徴づけ ) を実施する.
- CO2,CO,ニトリル,アルデヒドなどの基質との様々な挿入反応による反応性の調査.
主要な成果:
- ボロンアミジナートHC(RN) 2B(C6F5) 2 [R = iPr (1), tBu (2) ]が成功して合成されました.
- 化合物1と2は,CO2,CO,CNtBu,ベンザルデヒド,MeCNとの様々な挿入反応を示した.
- 化合物1の熱解は,一時的な"オープンチェーン"形態の関与を示唆する製品を生成しました.
結論:
- 合成されたボロンアミディナートは,さまざまな挿入反応を起こすことができる多機能なシントンである.
- 観察された反応性は,溶液中の"開鎖"形態の一時的な存在を支持する.
- この研究は,オーガノボロン化合物の既知の反応性を拡張し,それらの反応機構の洞察を提供します.
関連する概念動画
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.
01:38Preparation of Amines: Reductive Amination of Aldehydes and Ketones
Carbonyl compounds and primary amines undergo reductive amination first to produce imines, followed by secondary amines in the same reaction mixture, using selective reducing agents like sodium cyanoborohydride or sodium triacetoxyborohydride. Reductive amination produces different degrees of substitution of amines depending on the starting amine substrate.
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.
02:15Preparation 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...
02:23Alcohols from Carbonyl Compounds: Reduction
Reduction is a simple strategy to convert a carbonyl group to a hydroxyl group. The three major pathways to reduce carbonyls to alcohols are catalytic hydrogenation, hydride reduction, and borane reduction.
Catalytic hydrogenation is similar to the reduction of an alkene or alkyne by adding H2 across the pi bond in the presence of transition metal catalysts like Raney Ni, Pd–C, Pt, or Ru. Aldehydes and ketones can be reduced by this method, often under mild to moderate heat (25–100°C) and...
Catalytic hydrogenation is similar to the reduction of an alkene or alkyne by adding H2 across the pi bond in the presence of transition metal catalysts like Raney Ni, Pd–C, Pt, or Ru. Aldehydes and ketones can be reduced by this method, often under mild to moderate heat (25–100°C) and...