Protected Amine Synthesis Using Organic Carbonates Instead of Phosgene
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Solution Overview
Problem
Existing methods for preparing compounds containing aminocarbonyl moieties, such as urea, carbamate, or isocyanate moieties, rely heavily on phosgene, which is highly toxic and poses significant health risks, and the use of blocked isocyanates still requires the use of phosgene at some point in the manufacturing process.
Innovation Solution
A method using organic carbonates as a one-carbon synthon to prepare protected amines, such as blocked isocyanates, by reacting an organic carbonate with an active hydrogen compound and then with an amine, avoiding the use of phosgene and its derivatives, and allowing for the formation of protected amines with functional groups, including amino acids and amino acid esters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosgene is used to prepare compounds containing aminocarbonyl moieties, then the manufacturing process is established and efficient, but the toxicity and health risks to workers are high
Solution Approach 1:
The patent extracts and removes the harmful phosgene component from the synthesis pathway while retaining the useful carbonyl group functionality. This is achieved by using alternative carbonyl sources such as triphosgene (which releases phosgene in situ but allows controlled exposure) or other phosgene-free methods, thereby eliminating direct handling of toxic phosgene gas while maintaining manufacturing efficiency.
Solution Approach 2:
The patent introduces intermediary compounds such as carbonyldiimidazole or triphosgene as mediators that can transfer the carbonyl group without requiring direct use of phosgene. These intermediaries enable the formation of urea, carbamate, or isocyanate moieties through safer, more controllable reaction pathways that reduce worker exposure to toxic substances.
2Ease of manufacture
If blocked isocyanates are prepared from free isocyanates, then the blocking process is simple, but the use of phosgene is still required in the manufacturing process
Solution Approach 1:
The patent applies preliminary action by preparing protected amino acid esters or other amine precursors through phosgene-free methods before the blocking step. This allows the subsequent blocking process to remain simple while eliminating the need for phosgene in the overall manufacturing sequence. The amine component is pre-prepared in a protected form that can be directly blocked without generating free isocyanates.
Solution Approach 2:
The patent extracts the phosgene dependency from the blocking process by using alternative carbonyl sources. The blocking agent reacts with pre-prepared amines or protected amines through carbonyl transfer reactions that do not require phosgene, thereby maintaining the simplicity of the blocking step while eliminating toxic substance usage.
3Reliability
If activated amino acid esters are prepared using carbonyldiimidazole, then the activation is effective, but the method does not tolerate free carboxylic acid groups
Solution Approach 1:
The patent applies segmentation by separating the activation step from the presence of free carboxylic acid groups. Protected amino acid esters are used where the carboxylic acid functionality is already protected as an ester or other stable derivative. This allows carbonyldiimidazole or similar activating agents to effectively activate the amine component without interfering with or being interfered by free carboxylic acid groups, thereby maintaining both effectiveness and functional group tolerance.
Solution Approach 2:
The patent applies local quality by ensuring that only the specific functional group requiring activation (the amine or hydroxyl group adjacent to the carbonyl) is in the reactive form, while other functional groups such as carboxylic acids remain protected. This localized reactivity allows effective activation at the target site without the complications arising from free carboxylic acid groups elsewhere in the molecule.
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 method provides a safer, more environmentally friendly, and efficient process for producing protected amines, including blocked isocyanates, with minimal by-products and tolerance to various functional groups, using sustainable carbon sources and mild reaction conditions.
Implementation Method 1
reacting, in a liquid medium, the organic carbonate A provided in step a) with an active hydrogen compound B, thereby obtaining a precursor C
Implementation Method 2
reacting the precursor C obtained in step b) with an amine D having one or more -NH2 groups, thereby obtaining the protected amine
Data Source
AI summary
The present invention relates to the field of synthetic organic chemistry, in particular to a process for preparing protected amines, such as blocked isocyanates and protected amino acids or amino acid esters. More in particular, the present invention relates to a process which is safer, practical and more environmentally friendly compared to those in the state of the art, and that avoids the use of phosgene, directly or indirectly, and free isocyanates. The present invention further relates to protected amines obtainable by the method, in particular to protected amino acids and amino acid esters. The present invention also relates to protected oligopeptides, and a method to prepare them starting from protected amino acids or amino acid esters.