Stereocontrolled conjugate additions to dihydroindolizinone systems. Synthesis of enantiopure polysubstituted tetrahydropyrrolo[2,1-a]isoquinolones |
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Authors: | Cristina Camarero Inés González-Temprano Asier Gómez-SanJuan Sonia Arrasate Esther Lete Nuria Sotomayor |
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Institution: | Departamento de Química Orgánica II, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Euskal Herriko Unibertsitatea, Apdo. 644, 48080 Bilbao, Spain |
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Abstract: | Conjugate addition reactions of various types of nucleophiles to the γ-lactam unit of dihydroindolizinone systems have been studied. The addition of cuprates, amines or stabilized carbanions requires the activation of the unsaturated bicyclic lactam with a EWG at C-2, while sulfur-stabilized carbanions are reactive enough to add to the unsubstituted lactam. The stereochemical outcome of the conjugate addition reaction depends on the nature of the substituent at the angular position, and the incoming nucleophile. Thus 1,10b-cis or 1,10b-trans diastereomers could be obtained selectively with dr>95:5. The tandem conjugate addition–alkylation also takes place in good yields. These reactions have been applied to the synthesis of enantiopure tetrahydropyrrolo2,1-a]isoquinolines. |
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