キラルリチウムアミド集積物に対するステリック因子の影響
Chicheung Su1, Russell Hopson, Paul G Williard
1Department of Chemistry, Brown University , 324 Brook Street, Providence, Rhode Island 02912 United States.
Journal of the American Chemical Society
|January 24, 2014
まとめ
キラルリチウムアミドにおけるステリック阻害は,n-ブチルリチウムとの結合状態を決定する. 阻害が少ないアミドは2:2アグリゲットを形成し,ステリック量が増えたアグリゲットは2:1混合アグリゲットを好み,溶液構造に影響を与えます.
科学分野:
- 有機金属化学 有機金属化学
- 超分子化学 超分子化学
- NMRスペクトロスコーピ NMRスペクトロスコーピ
背景:
- チラルリチウムアミドは,非対称合成における重要な中間物質である.
- 溶液中のそれらの集積行動を理解することは,反応性を制御するために非常に重要です.
- オーガノリチウム反応剤を混ぜた集積物は,独特の構造的,化学的特性を表すことができます.
研究 の 目的:
- キラルリチウムアミドとn-ブチルリチウムの間で形成される混合集積物の溶液構造を調査する.
- 集積状態の制御におけるステリック障害の役割を解明する.
- キラルアミドの置換物の性質と構造的特徴を相関させる.
主な方法:
- 拡散係数-重量式 (D-FW) 相関関係による拡散順序によるNMR (DOSY) を含む核磁共振 (NMR) スペクトロスコピー.
- 1次および2次元のNMR技術が採用されました.
- トロウレン-d8溶液中の集積物の特性.
主要な成果:
- 混合集積物の集積状態は,キラルリチウムアミドのR1およびR2グループのステリック阻害によって制御されます.
- リチウム (S) -N-イソプロピル-1-((トライソプロピルシリル) オキシ) プロパン-2-アミドは,R2が阻害されることが少ないとき,n-ブチルリチウムと2:2の梯子型混合集積物を形成します.
- ステリック阻害の増大は,2:1混合集積物の形成を促進し,最も阻害されたアミドでは2:1の集積物のみが観察された.
結論:
- ステリック・バルクは,これらの混合リチウムアミド-n-ブチルリチウム系における集積数と構造の主要な決定因子である.
- 2:2から 2:1の集積への移行は,ステリック需要の増加とともに起こります.
- この発見は,キラルオーガノリチウム種の溶液状態の自己組み立てに関する洞察を提供します.
関連する概念動画
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
8.1K
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
8.1K
Prochirality
4.0K
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
4.0K
Amides to Amines: LiAlH4 Reduction
5.6K
Amide reduction with strong reducing agents like lithium aluminum hydride proceeds through a nucleophilic acyl substitution to form amines. Primary, secondary, and tertiary amides yield primary, secondary, and tertiary amines, respectively.
Amide reduction requires two equivalents of the reducing agent, acting as a source of hydride ions. As shown in the figure, the reaction is initiated with a nucleophilic attack by the hydride ion at the carbonyl carbon to form a tetrahedral intermediate.
Amide reduction requires two equivalents of the reducing agent, acting as a source of hydride ions. As shown in the figure, the reaction is initiated with a nucleophilic attack by the hydride ion at the carbonyl carbon to form a tetrahedral intermediate.
5.6K
Molecules with Multiple Chiral Centers
11.6K
Molecules that possess multiple chiral centers can afford a large number of stereoisomers. For instance, while some molecules like 2-butanol have one chiral center, defined as a tetrahedral carbon atom with four different substituents attached, several molecules like butane-2,3-diol have multiple chiral centers. A simple formula to predict the number of stereoisomers possible for a molecule with n chiral centers is 2n. However, there can be a lower number where some of the stereoisomers are...
11.6K
Chirality in Nature
13.5K
Chirality is the most intriguing yet essential facet of nature, governing life’s biochemical processes and precision. It can be observed from a snail shell pattern in a macroscopic world to an amino acid, the minutest building block of life. Most of the snails around the world have right-coiled shells because of the intrinsic chirality in their genes. All the amino acids present in the human body exist in an enantiomerically pure state, except for glycine - the sole achiral amino acid.
13.5K
Structure of Amines
2.5K
The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’...
2.5K


