Copper-Catalyzed C-H Amination Using Unactivated Amines
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Solution Overview
Problem
Current C—H amination methods require highly functionalized precursors and expensive, environmentally unfriendly oxidants, and are limited to primary amines and organoazides, with a need for methods that avoid these limitations and enable amination of unactivated substrates and aldehydes.
Innovation Solution
A metal-catalyzed C—H amination process using primary or secondary amines, peroxides as oxidants, and copper-based catalysts, which avoids the need for highly functionalized precursors and organoazides, allowing for the amination of a wide range of substrates, including unactivated ones and aldehydes, with easy-to-remove oxidants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If highly functionalized nitrene precursors (e.g., sulfonylamines) are used with expensive rhodium catalysts, then C—H amination can be achieved with good selectivity, but the process becomes expensive and requires environmentally unfriendly oxidants
Solution Approach 1:
The patent replaces expensive rhodium catalysts with inexpensive copper catalysts (e.g., Cu(OAc)2, CuCl2). The copper catalyst system achieves comparable C—H amination selectivity without requiring expensive metal complexes, thereby reducing process cost while maintaining manufacturing precision
Solution Approach 2:
The patent changes the oxidant from environmentally unfriendly reagents (e.g., PhI(OAc)2) to environmentally friendly alternatives (e.g., H2O2, O2, tBuOOH). This parameter change maintains the C—N bond formation efficiency while improving environmental compatibility and reducing process cost
2Productivity
If electron-deficient nitrene precursors are used, then C—H amination reactions proceed efficiently, but additional deprotection steps are required to obtain primary amines
Solution Approach 1:
The patent extracts the electron-deficient sulfonyl group from the nitrene precursor, using simple primary or secondary amines instead. This eliminates the need for additional deprotection steps while maintaining reaction efficiency through the copper-catalyzed mechanism that directly generates the desired amine product
Solution Approach 2:
Instead of using electron-deficient amines and then removing the electron-withdrawing group, the patent inverts the approach by using electron-rich primary or secondary amines directly. The copper catalyst enables these normally unreactive amines to participate in C—H amination without requiring prior functionalization or subsequent deprotection
3Productivity
If activated secondary amines with electron-withdrawing groups are used, then C—H amination can occur, but atom economy is reduced due to the need for deprotection
Solution Approach 1:
The patent uses simple, inexpensive primary or secondary amines as nitrene precursors instead of activated amines requiring deprotection. This eliminates waste from protecting group removal and improves atom economy while maintaining reaction feasibility through copper catalysis
Solution Approach 2:
The patent eliminates the need to discard protecting groups by using amines that do not require protection. The straightforward copper-catalyzed C—H amination of primary or secondary amines with substrates like ethylbenzene directly yields the desired product without generating deprotection waste
4Productivity
If expensive rhodium catalysts are used in low concentrations (2-5 mol %), then C—H amination achieves good yields, but the process becomes economically unattractive
Solution Approach 1:
The patent replaces expensive rhodium catalysts with inexpensive copper catalysts that can be used at similar or higher concentrations (5-20 mol %). This substitution maintains high amination yields while dramatically improving economic viability, making the process suitable for industrial application
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides high yields and selectivity in C—H amination reactions, reducing by-products and environmental impact, and allows for the use of inexpensive catalysts, making the process more economically and environmentally friendly.
Implementation Method 1
Copper is a particularly attractive metal for catalysis, approximately 10,000-25,000 times less expensive than rhodium. Using an inexpensive, easy-to-prepare β-diketiminate supporting ligand, dicopper nitrenes [Cu]2(μ-NR) have been identified as meta-stable isolable intermediates in C—H amination reactions.
Implementation Method 2
Heating a number of neat substrates with N3Ad in the presence of 2.5 mol % {[Cl2NN]Cu}2(benzene) gives rise to high amination yields.
Data Source
AI summary
One aspect of the invention relates to a method of animation or amidation, comprising the step of combining a substrate, comprising a reactive C—H bond, and an amine or amide, comprising a reactive N—H bond, in the presence of an oxidizing agent and a metal-containing catalyst, thereby forming a product with a covalent bond between the carbon of the reactive C—H bond and the nitrogen of the reactive N—H bond.