挫折したベータ塩化物除去. アルファ-クロロノルボルネンによる選択的アレンアルキル化が,電性メタルロセニウムイオンペアによって触媒化された
Aswini K Dash1, Tryg R Jensen, Charlotte L Stern
1Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA.
Journal of the American Chemical Society
|September 30, 2004
まとめ
新しいシングルサイトポリメリゼーション触媒は,アルファ-クロロノルボルネンでアロマティック分子を効率的にアルキル化します. これらの触媒は,高回転周波数を持つエクソ-1-クロロ-2-アリルノルボルナン製品を,地域選択的に生成します.
科学分野:
- 有機金属化学 有機金属化学
- カタリシス カタリシス カタリシス
- オーガニック・シンセシス オーガニック・シンセシス
背景:
- シングルサイトポリメリゼーション触媒は,ポリマー構造の正確な制御を提供します.
- メタロセンおよび関連する複合体は,有機変換における多用途な触媒である.
- 協調しないカウンターイオンによる金属アルキル複合体の活性化により,高度に電愛性の種が生成されます.
研究 の 目的:
- アロマティックアルキレーションのための新しい単一サイトポリメリゼーション触媒の触媒活性を調査する.
- アルキル化反応の地域選択性とステレオ選択性を探求する.
- 反応機構を解明し,重要な中間物質を特定する.
主な方法:
- Cp * MMe ((3), (CGC) MMe ((2)),Cp ((2)) ZrMe ((2) の前駆体 (M = Ti, Zr) から,シトウで触媒を生成する.
- Ph ((3) C (((+)) B (((C ((6) F ((5)) ((4))) または孤立したイオン対複合体を用いた活性化.
- アロマティック分子 (ベンゼン,トルエール) がアルファ-クロロノルボレンと反応する.
- NMR,GC-MS,および元素解析を用いた製品の特徴づけ.
- 2D NMRとX線結晶学による立体化学分析.
主要な成果:
- 触媒は地域選択的に,エクソ-1-クロロ-2-アリルノルボナンの製品を良好な収穫量で供給します.
- デュテリウムラベルを貼った製品は,デュテラートアロマティック溶媒を用いて合成されました.
- 120h ((-1) を超える高回転頻度が観察されました.
- アリルグループの立体化学は,exoであることが確認されました.
- このメカニズムは,金属の電愛好者の参加を伴う可能性が高い.
結論:
- 新しい単一サイト触媒は,芳香質の地域選択性アルキル化に有効です.
- 反応は,高いエクソステレオ選択性で進行する.
- 触媒システムは高効率で,有機合成におけるさらなる開発の可能性を示しています.
関連する概念動画
Hydroboration-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.
Alkynes 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.
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for the...
Radical Substitution: Allylic Bromination
In organic synthesis, the formation of products can be altered by changing the reaction conditions. For example, a dibromo addition product is formed when propene is treated with bromine at room temperature. In contrast, propene undergoes allylic substitution in non-polar solvents at high temperatures to give 3-bromopropene. In order to avoid the addition reaction, the bromine concentration must be kept as low as possible throughout the reaction. This can be achieved using N-bromosuccinimide...
Radical Substitution: Hydrogenolysis of Alkyl Halides with Tributyltin Hydride
Radical substitution reactions can be used to remove functional groups from molecules. The hydrogenolysis of alkyl halides is one such reaction, where the weak Sn–H bond in tributyltin hydride reacts with alkyl halides to form alkanes. Here, the reagent Bu3SnH yields tributyltin halide as a byproduct.
The bonds formed in this reaction are stronger than the bonds broken, making it energetically favorable. The reaction follows a radical chain mechanism similar to radical halogenation reactions,...
The bonds formed in this reaction are stronger than the bonds broken, making it energetically favorable. The reaction follows a radical chain mechanism similar to radical halogenation reactions,...


