Mandal PK, Katukojvala S. Rh-Catalyzed Chemodivergent [3+3] Annulations of Diazoenals and α-Aminoketones: Direct Synthesis of Functionalized 1,2-Dihydropyridines and Fused 1,4-Oxazines.
Chemistry 2024;
30:e202303862. [PMID:
38165004 DOI:
10.1002/chem.202303862]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 12/25/2023] [Accepted: 01/02/2024] [Indexed: 01/03/2024]
Abstract
Novel rhodium-catalyzed [3+3] annulations of diazoenals and α-amino ketones has been disclosed here. The reactivity of diazoenals has been switched from carbenoid to vinylogous NH-insertion by altering acyclic to cyclic α-amino ketones. In this direction, we report an efficient strategy to synthesize 1,2-dihydropyridines (DHPs) and fused 1,4-oxazines. Mechanistic investigation revealed that the formyl group is necessary for carbenoid [3+3] annulation and the cyclohexyl group is the dictating factor for vinylogous NH- insertion. The synthetic utility of 1,2-dihydropyridines was demonstrated by synthesizing piperidine, pyrido[1,2-a]indole, and 2-pyridone scaffolds. Further, structural diversification of fused 1,4-oxazines resulted in the short synthesis of hexahydroquinolin-2(1H)-ones, hexahydro quinolines and tetrahydroquinolinones via ring opening rearrangement and a new oxidative deformylation, respectively.
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