对酸和盐的基介导化过程的机械见解
Arianna Montoli1, Alessandro Dimasi1, Miriana Guarnaccia1
1Department of Chemistry, Università degli Studi di Milano Via Camillo Golgi, 19 20133 Milano Italy valerio.fasano@unimi.it https://www.fasanolab.com.
RSC advances
|January 13, 2025
概括
这项研究探讨了使用新型盐的基催化化的化. 这些化合物在特定位置选择性地增强了的结合,克服了先前在化功能化的局限性.
科学领域:
- 有机化学 有机化学
- 催化剂是一种催化剂.
- 同位素标记的标记
背景情况:
- 皮里丁的化对于各种应用至关重要,包括药物开发和机理学研究.
- 之前的远程位点化方法缺乏区域选择性,经常产生和替代产品的混合物.
- 在脱二甲基硫氧化物 (DMSO-d6) 中使用三甲氧化物 (KOtBu) 是一种已知的,但非选择性的方法.
研究的目的:
- 开发一种区域选择性方法,用于在偏远位置对二烯的化.
- 通过使用新型酸盐来研究基质催化化机制.
- 通过计算和实验验证这些盐在指导合物的有效性.
主要方法:
- 一系列具有临时电子吸收组的基盐的合成和表征.
- 计算研究 (例如,DFT) 以了解电子效应和反应途径.
- 在基本条件下使用这些盐的实验性化反应,然后进行分析 (例如,NMR光谱学).
主要成果:
- 设计的酸盐有效地阻断了对位,并增加了其他位点的酸度.
- 在pyridines的元位置实现了高效率的区域选择性化.
- 计算和实验数据证实了拟议的机制和开发的方法的有效性.
结论:
- 胺酸盐提供了一个强大的策略,以实现pyridines的区域选择性化.
- 这种方法克服了非选择性方法的局限性,允许精确的同位素标记.
- 这些发现为合成用于各种化学应用的特异酸衍生物开辟了新的途径.
相关概念视频
02:42Acidity of 1-Alkynes
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The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
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01:25Basicity of Heterocyclic Aromatic Amines
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Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).
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01:371° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism
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Nitrous acid is a relatively weak and unstable acid prepared in situ by the reaction of sodium nitrite and cold, dilute hydrochloric acid. In an acidic solution, the nitrous acid undergoes protonation when it loses water to form a nitrosonium ion—an electrophile. Nitrous acid reacts with primary amines to give diazonium salts. The reaction is called diazotization of primary amines.
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01:21Basicity of Aliphatic Amines
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Amines can behave as Brønsted–Lowry bases by accepting a proton from the acid to form corresponding conjugate acids. Due to a lone pair of nonbonding electrons, aliphatic amines can also act as Lewis bases by forming a covalent bond with an electrophile.
To measure the basicity of amines, two conventions are generally used. The first defines Kb as the basicity constant for the deprotonation reaction of water by the amine, as presented in Figure 1. Conventionally, lower Kb indicates...
To measure the basicity of amines, two conventions are generally used. The first defines Kb as the basicity constant for the deprotonation reaction of water by the amine, as presented in Figure 1. Conventionally, lower Kb indicates...
5.7K
01:19Diazonium Group Substitution: –OH and –H
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Nitrous acid, a weak acid, is prepared in situ via the reaction of sodium nitrite with a strong acid under cold conditions. This nitrous acid prepared in situ reacts with primary arylamines to form arenediazonium salts. Such reactions are known as diazotization reactions. As shown in Figure 1, the formation of arenediazonium salts begins with the decomposition of nitrous acid in an acidic solution to give nitrosonium ions.
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01:28Amides to Carboxylic Acids: Hydrolysis
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Amides can undergo either acid-catalyzed hydrolysis or base-promoted hydrolysis through a typical nucleophilic acyl substitution. Each hydrolysis requires severe conditions.
Acid-catalyzed hydrolysis:
Hydrolysis of amides under acidic conditions yields carboxylic acids. Since the reaction occurs slowly, hydrolysis requires the conditions of heat.
The mechanism begins with the protonation of the carbonyl oxygen by the acid catalyst. The protonation makes the amide carbonyl carbon more...
Acid-catalyzed hydrolysis:
Hydrolysis of amides under acidic conditions yields carboxylic acids. Since the reaction occurs slowly, hydrolysis requires the conditions of heat.
The mechanism begins with the protonation of the carbonyl oxygen by the acid catalyst. The protonation makes the amide carbonyl carbon more...
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