Direct synthetic route to functionalized 1,2-azaborinines

Area of Science:

• Organometallic Chemistry
• Synthetic Organic Chemistry
• Heterocyclic Chemistry

Background:

• 1,2-Azaborinines are a class of nitrogen- and boron-containing heterocycles.
• Developing efficient synthetic routes to functionalized azaborinines is crucial for exploring their chemical properties and potential applications.

Purpose of the Study:

• To develop a new catalytic synthetic route to functionalized 1,2-azaborinines.
• To synthesize the first examples of ferrocene-functionalized azaborinines.
• To investigate the regioselectivity and explore further transformations of the azaborinine products.

Main Methods:

• [2+2]/[2+4] cycloaddition reactions of di-tert-butyliminoboranes and alkynes.
• Utilizing a rhodium catalyst for the cycloaddition.
• Thermolytic conditions for subsequent transformations.
• Theoretical studies to elucidate reaction mechanisms.

Main Results:

• A new catalytic synthetic route to functionalized 1,2-azaborinines was established.
• The first ferrocene-functionalized azaborinines were synthesized.
• Regioselectivity control was achieved via a rhodium 1,2-azaborete intermediate, leading to the isolation of the first azaborinine boronic ester.
• An NH-containing BN isostere was isolated through thermolytic elimination of isobutene.

Conclusions:

• The developed rhodium-catalyzed cycloaddition provides a versatile method for synthesizing diverse 1,2-azaborinines.
• The study demonstrates the feasibility of incorporating ferrocene moieties and accessing unique BN isosteres.
• Theoretical insights support the proposed reaction pathways and product formations.