連続C-Hアリレーションによるテトラアリルチオフェンのプログラム合成
Shuichi Yanagisawa1, Kirika Ueda, Hiromi Sekizawa
1Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan.
Journal of the American Chemical Society
|October 1, 2009
まとめ
新しい方法により,地域選択性C−Hアリレーションによってテトラアリルチオフェンのプログラム合成が可能になった. この研究は,複雑な代用チオフェン構造を作り出すための金属およびリガンド制御反応を明らかにしています.
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:
- チオフェン誘導体は,医薬品化学と材料科学における重要な支架である.
- テトラアリルチオフェンを合成するための効率的で地域選択的な方法は限られている.
研究 の 目的:
- テトラアリルチオフェンのプログラム合成のための一般的なプロトコルを作成する.
- 金属とリガンドによって制御される地域差異性C−Hアリレーションを調査する.
主な方法:
- 3つの触媒システムを利用しました:RhCl(CO) {P[OCH(CF3)2]3}2,PdCl2/P[OCH(CF3)2]3,そしてPdCl2/bipy.
- 3メトキシチオフェンのC-H結合でヨドアレネスとの領域選択的な配列アリレーションを行いました.
- 第4アリル基を設置するためにデメチル化,トリフレーション,スズキ-ミヤウラ結合を用いた.
主要な成果:
- 連続C−Hアリレーションによるテトラアリルチオフェンのプログラム合成を達成した.
- メタルとリガンド制御の地域多様性アリレーション経路を発見.
- 2,4,5-トリアリル-3-メトキシチオフェン,その後テトラアリルチオフェンを成功して合成した.
結論:
- 開発されたプロトコルは,テトラアリルチオフェンへの汎用的な経路を提供します.
- この研究は,地域選択性を制御する際に,触媒とリガンドの選択の重要性を強調しています.
- この研究は,高度に置換されたチオフェン誘導体を構築するための合成ツールボックスを拡張します.
関連する概念動画
02:27Preparation of Alkynes: Alkylation Reaction
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
01:18Aromatic Hydrocarbon Cations: Structural Overview
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group with both...
Removing one hydrogen from the intervening CH2 group with both...
01:16Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
02:34Preparation of Alkynes: Dehydrohalogenation
Introduction
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.