N-Heterocyclic-Carbene-Catalyzed Domino Reactions via Two or More Activation Modes
Xiang-Yu Chen1, Sun Li1, Fabrizio Vetica1
1Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany.
Iscience
|November 15, 2018
Summary
N-heterocyclic carbenes (NHCs) catalyze efficient domino reactions, rapidly building complex molecules. These organocatalytic processes offer mild conditions, simple procedures, and excellent stereocontrol.
Area of Science:
- Organic Chemistry
- Catalysis
- Synthetic Chemistry
Background:
- Organocatalytic domino processes are a rapidly expanding research field.
- N-heterocyclic carbenes (NHCs) are versatile organocatalysts with broad applications.
- NHC-catalyzed domino reactions have advanced significantly in the past decade.
Purpose of the Study:
- To review recent advances in N-heterocyclic carbene (NHC)-catalyzed domino reactions.
- To highlight the scope, limitations, and mechanisms of these transformations.
- To focus on the characteristics of reaction substrates in NHC-catalyzed domino sequences.
Main Methods:
- Literature review of NHC-catalyzed domino reactions.
- Analysis of reaction scope and substrate features.
- Discussion of reaction mechanisms and limitations.
Main Results:
- NHC-catalyzed domino reactions enable the rapid assembly of complex molecular scaffolds.
- These processes combine different activation modes effectively within a single reaction.
- Excellent stereocontrol is achieved under mild reaction conditions.
Conclusions:
- NHC-catalyzed domino reactions are powerful tools in synthetic chemistry.
- The accessibility of catalysts and substrates, along with simple procedures, makes these reactions attractive.
- Further research into substrate features can optimize these domino sequences.
Related Concept Videos
01:08Base-Catalyzed Aldol Addition Reaction
4.6K
As depicted in Figure 1, base-catalyzed aldol addition involves adding two carbonyl compounds in aqueous sodium hydroxide to form a β-hydroxy carbonyl compound.
4.6K
01:15Acid-Catalyzed Aldol Addition Reaction
3.3K
The aldol reaction of a ketone under acidic conditions successfully forms an unsaturated carbonyl as the final product instead of an aldol. The acid-catalyzed aldol reaction is depicted in Figure 1.
3.3K
01:25Basicity of Heterocyclic Aromatic Amines
7.0K
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).
7.0K
01:07What is a Mode?
26.0K
The mode is one of the commonly used measures of a central tendency. It is defined as the most frequent value in a data set.
There can be more than one mode in a data set if multiple values have the same highest frequency. For instance, suppose that the Statistics exam scores of 20 students are: 50; 53; 59; 59; 63; 63; 72; 72; 72; 72; 72; 76; 78; 81; 83; 84; 84; 84; 90; 93. Here, the mode is 72, as it occurs most frequently, five times.
A data set with two modes is called bimodal. For example,...
There can be more than one mode in a data set if multiple values have the same highest frequency. For instance, suppose that the Statistics exam scores of 20 students are: 50; 53; 59; 59; 63; 63; 72; 72; 72; 72; 72; 76; 78; 81; 83; 84; 84; 84; 90; 93. Here, the mode is 72, as it occurs most frequently, five times.
A data set with two modes is called bimodal. For example,...
26.0K
01:10Nomenclature of Aryl and Heterocyclic Amines
3.2K
The simplest aromatic amine is phenylamine, which contains an –NH2 functionality directly attached to an aromatic ring. The name aniline is designated for this skeleton. As shown in Figure 1, the common names of the functionalized anilines involve prefixes ortho-, meta-, and para- to indicate the substitution position. Different functionalized aniline derivatives also have notable trivial names.
3.2K
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
4.5K
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.
4.5K