Copper and Rhodium Relay Catalysis for Selective Access to cis-2,3-Dihydroazepines
You Li1, Han Luo1, Zongyuan Tang1
1School of Chemistry and Chemical Engineering, Chongqing University, 174 Shazheng Street, Chongqing 400044, China.
Abstract:
A new catalytic protocol to access synthetically challenging cis-2,3-dihydroazepines is reported. The reaction starts with readily available dienals, alkynes, and sulfonyl azides as the substrates and employs copper and rhodium as relay catalysts. Key steps include a copper-catalyzed reaction between an alkyne and a sulfonyl azide to form a triazole intermediate. The subsequent activation of this triazole intermediate by a rhodium catalyst, followed by a reaction with the dienal substrate, eventually leads to the dihydroazepine product. The regio- and stereochemistries of the products are believed to be controlled through a stereospecific conrotatory 8π-electrocyclization process against a possible competing 6π-electrocyclization process.
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