Panda S, Gayen U, Ghorai P. Organocatalytic Desymmetric Conjugate Addition to Cyclobutanone: An Enantio- and Diastereoselective Synthesis of [6,5,4]-Fused Carbocycles.
Chemistry 2023;
29:e202203407. [PMID:
36694942 DOI:
10.1002/chem.202203407]
[Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 01/24/2023] [Accepted: 01/24/2023] [Indexed: 01/26/2023]
Abstract
The first organocatalytic, non-destructive desymmetrisation of 3-substituted cyclobutanone followed by intramolecular cyclisation is described. Owing to the slow activation of the pronucleophile by the weak Brønsted base, the α-functionalization of ketones with tertiary-amine-derived Brønsted base catalysis has been chemically challenging in asymmetric transformations. Herein, we demonstrate that the cinchona-derived squaramide catalyst works effectively for the intramolecular Michael addition of cyclobutanone to enones and affords the architecturally fascinating [6,5,4]-fused carbocyclic skeleton in good yields and excellent diastereo- and enantioselectivities (up to >20 : 1 dr and 96 % ee). Furthermore, as a synthetic application, this method provides an alternative pathway to enantioenriched high-value products like γ-lactones and indan-2-ol derivatives.
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