Substrate-Switched Chemodivergent Pyrazole and Pyrazoline Synthesis: [3+2] Cycloaddition/Ring-Opening Rearrangement Reaction of Azadienes with Nitrile Imines

By virtue of a fundamentally new reaction model of benzofuran-derived azadienes (BDAs), an unprecedented synthesis of biologically important pyrazoles has been achieved through a tandem [3 + 2] cycloaddition/ring-opening rearrangement reaction of BDAs with nitrile imines. The nature and type of substrates are found to act as a chemical switch to trigger two distinct reaction pathways. A minor modification to the substrates allows the access to spiro-pyrazolines.

Automated summary

A fundamentally new reaction model of benzofuran-derived azadienes (BDAs) has led to the synthesis of biologically important pyrazoles through a tandem [3 + 2] cycloaddition/ring-opening rearrangement reaction with nitrile imines. The nature and type of substrates determine two distinct reaction pathways, and minor modifications to the substrates allow access to spiro-pyrazolines.