Synthesis of 2-(1-(tert-butoxycarbonyl)piperidine-4-yl)benzoic Acid
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Solution Overview
Problem
There is a need for new efficient processes to prepare 2-(1-(tert-butoxycarbonyl)piperidine-4-yl)benzoic acid, which is an intermediate for producing ampreloxetine and its salts, as existing methods may not be sufficiently efficient or effective.
Innovation Solution
A multi-step process involving reactions with C1-6 alkyl 3-oxobutanoate, alkali metal hydroxide, ammonia reagents, reducing agents, di-tert-butyl dicarbonate, and alkyl lithium reagents, culminating in the formation of 2-(1-(tert-butoxycarbonyl)piperidine-4-yl)benzoic acid, with specific conditions and reagents such as piperidine, potassium hydroxide, urea, sodium borohydride, and n-butyl lithium to enhance yield and reduce waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing methods are used to prepare 2-(1-(tert-butoxycarbonyl)piperidine-4-yl)benzoic acid, then the process can be completed, but the efficiency and yield are insufficient
Solution Approach 1:
The synthesis process is divided into multiple discrete steps: (a) condensation of 2-bromobenzaldehyde with alkyl 3-oxobutanoate to form dialkyl 2,4-diacetyl-3-(2-bromophenyl)pentanedioate, (b) hydrolysis to form the diacid, (c) cyclization to form the piperidine dione, (d) reduction to the piperidine, (e) carbamate formation, (f) lithiation, and (g) carboxylation. Each step is optimized independently to maximize overall efficiency and yield.
Solution Approach 2:
The process employs preliminary protection of the piperidine nitrogen as a carbamate (tert-butoxycarbonyl group) before the final carboxylation step. This preliminary action prevents unwanted side reactions at the nitrogen center during the harsh lithiation and carboxylation conditions, ensuring higher yield and purity of the final product.
2Ease of manufacture
If conventional synthesis routes are used, then the process is simpler, but waste generation increases
Solution Approach 1:
The process utilizes specific parameter optimizations including: using C1-6 alkyl 3-oxobutanoate (methyl or ethyl) to facilitate easier hydrolysis and reduce waste; employing di-tert-butyl dicarbonate as the carbamating agent which provides stable protection and minimal byproducts; and using n-butyl lithium for controlled lithiation that minimizes side reactions and waste. These parameter changes maintain process simplicity while significantly reducing waste generation.
3Reliability
If existing preparation methods are used, then the process can proceed, but the overall yield is low
Solution Approach 1:
The synthesis employs continuous useful action through: (a) using excess alkyl 3-oxobutanoate in the condensation step to drive the reaction to completion, (b) performing hydrolysis under forced conditions with alkali metal hydroxide to ensure complete conversion, (c) using heating conditions for the cyclization step to maximize dione formation, and (d) employing excess di-tert-butyl dicarbonate in the carbamating step. Each step is driven to completion to maintain high overall yield and process efficiency.
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
The process provides an efficient and effective method for producing 2-(1-(tert-butoxycarbonyl)piperidine-4-yl)benzoic acid, improving the overall yield and reducing waste generation, making it a more viable intermediate for ampreloxetine synthesis.
Implementation Method 1
reacting a compound of formula 1: 2-bromobenzaldehyde with a C 1-6 alkyl 3-oxobutanoate in the presence of piperidine to form a compound of formula 2
Implementation Method 2
reacting the compound of formula 2 with an alkali metal hydroxide to form, after acidification of the reaction product with an acid, a compound of formula 3
Implementation Method 3
reacting the compound of formula 3 with an ammonia reagent to form a compound of formula 4
Implementation Method 4
reacting the compound of formula 4 with a reducing agent to form a compound of formula 5 or a salt thereof
Implementation Method 5
reacting the compound of formula 5 or a salt thereof with di-tert-butyl dicarbonate to form a compound of formula 6
Implementation Method 6
reacting the compound of formula 6 with an alkyl lithium reagent to form a compound of formula 7
Implementation Method 7
reacting the compound of formula 7 with carbon dioxide to form the compound of formula I
Data Source
AI summary
The invention relates to processes for preparing 2-(1-(tert-butoxycarbonyl)-piperidine-4-yl)benzoic acid having formula I: (I) Among its various uses, this compound is useful as an intermediate for preparing ampreloxetine and salts thereof.