Modular 1,2-Azaborine Synthesis via Ring-Opening BN-Isostere Benzannulation

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Solution Overview

Problem

The challenge lies in efficiently and modularly synthesizing monocyclic 1,2-azaborines, as existing methods are complex, require noble metals, and have limited scope and yield, hindering their application in medicinal chemistry.

Innovation Solution

A method involving the reaction of a Lewis acid, an N-substituted 1-cyclopropyl imine, and a B-substituted dihaloborane to form a B-substituted, N-substituted, 1-halo-N-(6-halohex-3-enyl)boranamine, followed by base treatment to produce 1,2-disubstituted azaborines under mild conditions, avoiding noble metals and allowing for broad substrate tolerance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If existing synthesis methods are used to prepare monocyclic 1,2-azaborines, then the compounds can be obtained, but the synthesis is complex, requires noble metals, and has limited scope and yield

Engineering Contradiction:

Improvesynthesis complexityVSAvoidsynthesis yield

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent changes the reaction parameters by using organometallic reagents (lithium, magnesium, or zinc halides) instead of traditional methods requiring noble metal catalysts. This parameter change enables a modular synthesis approach with improved yields (up to 90%) and broader substrate scope while eliminating the need for complex multi-step sequences and expensive catalysts

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The synthesis is divided into discrete modular steps: (1) formation of organometallic reagent from cyclopropyl imine, (2) reaction with B-substituted dihaloborane, and (3) base treatment to furnish the final 1,2-azaborine. This segmentation allows each step to be optimized independently and facilitates easy modification for different substituents, thereby improving both ease of manufacture and productivity

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If existing synthesis methods are used, then B-alkoxy-1,2-azaborines can be accessed, but C-substituted 1,2-azaborines require an overall six-step sequence

Engineering Contradiction:

Improvesubstrate scopeVSAvoidsynthesis sequence length

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent employs a universal synthesis platform that works for both B-alkoxy and C-substituted 1,2-azaborines using the same three-step sequence. The method accepts various organometallic reagents (lithium, magnesium, or zinc halides) and B-substituted dihaloboranes with diverse substituents, providing a single versatile route that eliminates the need for different synthetic sequences for different substitution patterns

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent uses organometallic intermediates (lithium, magnesium, or zinc halides) as versatile mediators that can be generated from N-substituted 1-cyclopropyl imines and then reacted with B-substituted dihaloboranes. These intermediates serve as universal building blocks that facilitate the formation of both B-alkoxy and C-substituted 1,2-azaborines in a streamlined manner, reducing the synthesis sequence from six steps to three steps

Inventive Principle:

Principle #24Intermediary (Mediator)

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 a scalable, versatile, and efficient synthesis of diverse 1,2-azaborines with improved yield and functional group tolerance, facilitating their use in medicinal chemistry research.

Implementation Method 1

A method involving the reaction of a Lewis acid, an N-substituted 1-cyclopropyl imine, and a B-substituted dihaloborane to form a B-substituted, N-substituted, 1-halo-N-(6-halohex-3-enyl)boranamine

Methodology Applied

Scientific EffectLewis acid catalysis: Catalysis