title: Synthesis of C4 - C5 cycloalkyl-fused and C6-modified chromans via ortho-quinone methides.
abstract: Starting from 3,5-dimethoxybenzaldehyde, some functionalized 2,3,4-trisubstituted tricyclic 4,5-cycloalkyl-fused and 6-modified chromans could be prepared via ortho-quinone methides (o-QMs)/hetero-Diels-Alder (HDA) reactions of the appropriate precursors. The bromide at C6 served as a handle for introducing other substituents through palladium-catalyzed cross-coupling reactions and other functional-group transformations. Moderate to high yields (up to 80%) and diastereoselectivities (up to >99:1) could be obtained under [PtCl4 ] catalysis. The preferred endo transition state during the cycloaddition reaction played an important role in governing the stereochemical outcomes at C2 - C3 - C4. The configurationally fixed E geometry of the bicyclic o-QMs influenced the cycloaddition reactions to favor the C2 - C4 cis relationship.
authors: Laboratory of Medicinal Chemistry, Chulabhorn Research Institute, 54 Kamphaeng Phet 6 Road, Laksi, Bangkok 10210 (Thailand).
authors: Kassrin
authors: K
authors: Tangdenpaisal
authors: Kanokpish
authors: K
authors: Chuayboonsong
authors: Patchaya
authors: P
authors: Sukjarean
authors: Varisa
authors: V
authors: Katesampao
authors: Nok
authors: N
authors: Noiphrom
authors: Somsak
authors: S
authors: Ruchirawat
authors: Poonsakdi
authors: P
authors: Ploypradith
mesh_terms: D002384:Catalysis; D002839:Chromans / Q000138:chemical synthesis* / Q000737:chemistry; D045563:Indolequinones / Q000737:chemistry*; D015394:Molecular Structure; D010165:Palladium
chemical_list: D002839:Chromans; D045563:Indolequinones; C068040:quinone methide; D010165:Palladium
keywords: asymmetric synthesis; cycloaddition; heterocycles; heterogeneous catalysis; platinum