協調オキシボランの合成と特徴:ボロン-酸素二重結合のルイス酸安定化
Dragoslav Vidovic1, Jennifer A Moore, Jamie N Jones
1Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX 78712-0165, USA.
Journal of the American Chemical Society
|March 31, 2005
まとめ
研究者らは,塩化アルミニウム (AlCl3) 複合を用いて最初の安定したオキシボランモノマー (LB=O) を合成した. この画期的な発見は,ボロン-酸素の二重結合特性を有意に維持し,無機化学を進歩させた.
科学分野:
- 無機化学 無機化学とは
- 有機金属化学 有機金属化学
- コンピューティング・ケミストリー
背景:
- オキシボランは反応性のある種で,典型的にはポリマーとして存在します.
- モノメアオックスボランの安定化は,その高い反応性のために困難です.
- 以前の研究は,一時的または安定性の低い形態に焦点を当てていました.
研究 の 目的:
- 最初の安定したモノメリックオクソボランを合成し,特徴づけること.
- 安定したオクソボランの電子構造と結合を調査する.
- 反応性主群種を安定させるためのルイス酸複合化の有用性を探求する.
主な方法:
- 新しいリガンドL ([HC(CMe) 2 ((NC6F5) 2)) の合成.
- LAlCl2がボロン三塩化物 (BCl3) と反応し,その後に水解が行われます.
- 電子構造を分析するための密度関数理論 (DFT) 計算.
主要な成果:
- アルミニウム塩化物 (AlCl3) と複合した安定したオキシボランモノマー (LB=O) の成功調製.
- 特徴づけは,化合物のモノメア性および安定性を確認します.
- DFTの計算は,ボロン-酸素のダブルボンド特性を有意に示しています.
結論:
- AlCl3との複合は,オクソボラン単体を効果的に安定させます.
- この研究は,反応性主群化合物を分離し研究するための実行可能な戦略を示しています.
- この研究は,ボロン-酸素化合物の化学の新たな道を開く.
関連する概念動画
02:54Lewis Structures of Molecular Compounds and Polyatomic Ions
To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined:
02:52Resonance
The Lewis structure of a nitrite anion (NO2−) may actually be drawn in two different ways, distinguished by the locations of the N-O and N=O bonds.
02:16Resonance and Hybrid Structures
According to the theory of resonance, if two or more Lewis structures with the same arrangement of atoms can be written for a molecule, ion, or radical, the actual distribution of electrons is an average of that shown by the various Lewis structures.
Resonance Structures and Resonance Hybrids
The Lewis structure of a nitrite anion (NO2−) may actually be drawn in two different ways, distinguished by the locations of the N–O and N=O bonds.
Resonance Structures and Resonance Hybrids
The Lewis structure of a nitrite anion (NO2−) may actually be drawn in two different ways, distinguished by the locations of the N–O and N=O bonds.
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.
02:36Regioselectivity 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.
02:47Alkynes 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.