Amide Synthesis via Catalytic Hydrogenation Selectivity
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Solution Overview
Problem
The existing process for preparing 9-substituted pyrazolyl-4-carboxylic acid benzonorbornen-5-yl-amides results in low yields of the 9-monosubstituted regioisomer, making large-scale production economically unfavorable and inefficient.
Innovation Solution
A process involving the reaction of specific compounds with reducing agents and subsequent conversion using a compound of formula V, optimized to achieve high yields and selectivity for the 9-monosubstituted pyrazolyl-4-carboxylic acid benzonorbornen-5-yl-amides, including the use of hydrogenation steps with metal catalysts and specific solvents to control stereoisomer ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the existing process for preparing pyrazolyl-4-carboxylic acid benzonorbornen-5-yl-amides is used, then the production can be carried out, but the yield of 9-monosubstituted regioisomer is low making large-scale production economically unfavorable
Solution Approach 1:
The patent changes the reaction parameters by using specific reducing agents (hydrogen with metal catalysts like Pd/C, PtO2, or Rh/C) and controlling reaction conditions (solvents like methanol or ethyl acetate, temperature, pressure) to improve the yield of the desired 9-monosubstituted regioisomer from low yields to economically viable levels for large-scale production
Solution Approach 2:
The patent replaces conventional reduction methods with catalytic hydrogenation using metal catalysts, substituting traditional chemical reduction mechanisms with a more efficient catalytic process that provides better selectivity and yield for the target compound
2Manufacturing precision
If conventional reduction methods are used to prepare 5-amino-benzonorbornene, then both the nitro group and endocyclic double bond are reduced, but this leads to low selectivity and low yield of the desired product
Solution Approach 1:
The patent optimizes reaction parameters including using specific metal catalysts (Pd/C, PtO2, Rh/C), controlling solvent selection (methanol, ethyl acetate), temperature, and hydrogen pressure to achieve selective reduction that improves both manufacturing precision and productivity
Solution Approach 2:
The patent substitutes conventional non-catalytic or less efficient reduction methods with catalytic hydrogenation using metal catalysts, providing superior selectivity for reducing the nitro group while controlling the reduction of the endocyclic double bond, thereby improving both precision and yield
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 significantly improves the yield and quality of 9-monosubstituted pyrazolyl-4-carboxylic acid benzonorbornen-5-yl-amides, achieving high syn/anti ratios in favor of the syn isomer, which are valuable as fungicides for controlling fungus infestation in cultivated plants.
Implementation Method 1
catalytic reduction under standard conditions (for example, Ra/Ni or Pd/C) in a solvent (for example, methanol) reduces both the nitro group and the endocyclic double bond
Implementation Method 2
catalytic reduction under standard conditions (for example, Ra/Ni or Pd/C)
Data Source
AI summary
The present invention relates to a process for the preparation of compounds of formula Iwherein R1 and R2 are each independently of the other hydrogen or C1-C5alkyl and R3 is CF3 or CF2H, bya) reaction of a compound of formula IIwherein R1 and R2 are as defined for formula I, with at least one reducing agent to form a compound of formula IIIwherein R1 and R2 are as defined for formula I, andb) reaction of that compound with at least one reducing agent to form a compound of formula IVwherein R1 and R2 are as defined for formula I, and(c) reaction of that compound with a compound of formula Vwherein Q is chlorine, fluorine, bromine, iodine, hydroxy or C1-C6alkoxy and R3 is as defined for formula I, to form the compound of formula I;and to novel intermediates for use in that process.