内部和终端基的原子经济交叉合以获得1,3-基
Mingyu Liu1, Tianhua Tang1, Omar Apolinar1
1Department of Chemistry, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, California 92037, United States.
这项研究引入了一种新的催化方法,可以在不需要预先功能化的起始材料的情况下制造1,3. 这种高效的工艺简化了化学合成,
科学领域:
- 有机化学
- 催化剂
- 合成方法
背景情况:
- 选择性碳-碳 (C-C) 键形成通常需要预先功能化的构建块,从而降低合成效率.
- 在制药制造等大规模应用中,预功能化步骤特别低效.
- 开发绕过预功能化的方法对于简化复杂合成至关重要.
研究的目的:
- 开发一种用于合成1,3-的选择性和催化方法.
- 为了使未被激活的内部基与终端基在没有预功能化的情况下结合起来.
- 为进一步的化学转化提供多用途的1,3-enyne中间体.
主要方法:
- 终端捐助基与未激活的内部接受基 (包括基醇,氨基和胺) 的合.
- 使用量身定制的- (P,N) -连接物直接进行区域选择性添加.
- 采用通过氧化还原中性循环运行的 (II) 催化系统.
主要成果:
- 实现了高度区域和立体选择性的1,3-氨酸合成.
- 证明了广泛的可接受性基因,包括基衍生物.
- 该方法具有可扩展性,在低催化剂负载 (0.5mol%) 时有效,并抑制产品异构.
- 预先的机制研究支持Pd (II) 催化循环.
结论:
- 已经建立了一种新的,高效的,可扩展的方法来合成1,3-enynes,而无需预先功能化的构建块.
- 开发的P,N-连接物和催化系统使得高选择性和广泛的基质范围成为可能.
- 由此产生的1,3-是各种下游合成应用的有价值的中间体.
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相关概念视频
Preparation of Alkynes: Alkylation Reaction
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.
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
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
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.
Alkynes to Aldehydes and Ketones: Acid-Catalyzed Hydration
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
Nomenclature of Alkynes
Preparation of Alkynes: Dehydrohalogenation
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.
