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DOI: 10.1055/s-0034-1378401
Formal 1,2-Insertion of Rh(II) Azavinyl Carbenes into Formamides
Publication History
Publication Date:
18 July 2014 (online)
Significance
N-Sulfonylated 1,2,3-triazoles serve as versatile precursors for electrophilic rhodium azavinyl carbenes A, which can react with different weak unsaturated nucleophiles to furnish a variety of nitrogen-containing heterocycles. Previously, Fokin and co-workers reported the insertion of such rhodium carbenes into the O–H and N–H bonds of amides, carbamates and carboxylic acids (J. Am. Chem. Soc. 2014, 136, 195). Here, Lee and co-workers demonstrate a stereoselective formal 1,2-insertion of rhodium carbenes A into the C=O bond of a range of formamides. The method generates diamino enones with exclusive Z-selectivity.
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Comment
The proposed mechanism of the reaction begins with attack of rhodium azavinyl carbene A by the nucleophilic oxygen atom of formamide 1. The generated zwitterionic intermediate B can then cyclize to form 2-amino-4-oxazoline C, which possesses a weak N,O-hemiacetal functionality. The authors suggest a rearrangement of C to aziridine D, which then undergoes a ring-opening and tautomerization to the observed product 3. The products are formed in good to excellent yields with a wide array of electron-donating and -withdrawing substituents tolerated on the aromatic ring of the 1,2,3-triazole.
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