Mlostoń G, Celeda M, Palusiak M. Higher-order [8+2]-cycloadditions of tropothione with levoglucosenone (LGO) and structurally similar exo-cyclic enones derived from cyrene.
Carbohydr Res 2023;
529:108844. [PMID:
37210942 DOI:
10.1016/j.carres.2023.108844]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/09/2023] [Accepted: 05/14/2023] [Indexed: 05/23/2023]
Abstract
Levoglucosenone (LGO) and structurally similar exo-cyclic enones derived from cyrene (dihydrolevoglucosenone) react with tropothione following the higher-order [8 + 2]-cycloaddition pathway. Reactions were performed at room temperature in CH2Cl2 solutions in absence of any activating reagent. Whereas reaction of tropothione with LGO occurred with complete stereoselectivity, leading to a single, sterically favored exo cycloadduct, identified as polycylic thiophene derivative, reactions performed with exo-cyclic enones yielded in some instances mixtures of two isomeric exo and endo cycloadducts, derived from spiro-tetrahydrothiophene as major and minor components, respectively, of the studied reaction mixtures. Exo and endo [8 + 2] cycloadducts differ in absolute configuration at the newly created chiral centers. Structures of exo and endo cycloadducts were confirmed by single crystal X-ray diffraction analysis.
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