M=N(α) サイクル添加とN(α) -N(β) 挿入がアルキンとチタンヒドラジド化合物の反応:実験と計算による研究を組み合わせた研究
A Daniel Schofield1, Ainara Nova, Jonathan D Selby
1Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK.
Journal of the American Chemical Society
|July 13, 2010
まとめ
この研究では,アルキンとチタン水酸化物の新しい反応が明らかになり,アザトチタンサイクロブテンまたはビニルイミド化合物が形成されます. これらの反応には,サイクロアディションとN-N結合の挿入が含まれ,そのメカニズムはアリル置換物の電子効果の影響を受けます.
科学分野:
- 有機金属化学 有機金属化学
- タイタンの化学
- 合成有機化学 合成有機化学について
背景:
- タイタニウムヒドラジドは,有機金属化学における多用途リガンドである.
- アルキンなどの不飽和化合物と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.
研究 の 目的:
- ダイアミド-アミンのサポートされたチタン水酸化物と末端および内部アリルアルキネの反応を調査する.
- サイクル添加とN-N結合挿入経路を含む反応機構を明らかにする.
- アリル置換剤の電子効果が反応結果と地域化学に及ぼす影響を調査する.
主な方法:
- 組み合わせた実験研究と密度関数理論 (DFT) の計算.
- 異なる温度条件下で,様々なアリルアルキンとタイタン水化物複合体の反応.
- 反応産物の分析は,光譜技術とX線結晶学 (暗示) を用いて行われます.
- 活性化パラメータの決定 (ΔH‡, ΔS‡, ΔG‡) とハメット分析を含む運動学的研究.
主要な成果:
- 室温でTi=N(α) 結合にアルキンの [2+2] サイクル添加によるアザチタナ・サイクロブテンの形成.
- ビニルイミド化合物の形成は,高温または異なるチタン複合体による,N(α) -N(β) 結合への純挿入による.
- N-N結合の挿入は,アルキンサイクル添加を経て,その後に分子内N (α) 原子の移動が続くことを明らかにする機械的洞察.
- 電子を取り除くアリル群が中間物質を安定させ,地域化学を直接作用させ,電子を放出するアリル群がN(α) 移行段階を好むことを示す.
結論:
- この研究では,アルキンサイクル添加とN-N結合挿入を含む金属ヒドラジド反応の最初の例を提示しています.
- 反応のメカニズムは複雑で,初期サイクロアディションと,その後の分子内再構成を含む.
- アルキンに対する置換効果は,反応経路と製品分布を決定する上で重要な役割を果たします.
関連する概念動画
01:22Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
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.
02:24Reduction 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.
01:09Conjugate Addition to α,β-Unsaturated Carbonyl Compounds
α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in the molecule leads to three resonance structures. The hybrid form exhibits two probable electrophilic sites: the carbonyl carbon and the β carbon.
02:38Electrophilic Addition to Alkynes: Halogenation
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.