A novel vinylogous aldol addition of alkylidene oxindole with 1-trifluoromethyl-3-alkylidene-propan-2-ones is presented. The reaction, catalyzed by a bifunctional tertiary amine, provides an efficient application of the vinylogous reactivity of oxindoles for the preparation of enantioenriched trifluoromethylated allylic alcohols.
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http://dx.doi.org/10.1039/c8ra06615a | DOI Listing |
Org Lett
December 2024
Molecular Synthesis Center & Key Laboratory of Marine Drugs, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China.
A regiodivergent strategy for the asymmetric diversity-oriented synthesis of spirooxindoles via organocatalytic cascade reactions is developed. Two regioselective pathways can be precisely controlled with different aminocatalysts in the reaction of 2-hydroxycinnamaldehydes and β,β-disubstituted 3-alkylidene oxindoles. The cascade vinylogous Michael/oxa-Michael/aldol reactions gave spiro-bridged oxindoles bearing two adjacent quaternary stereocenters, while the cascade oxa-Michael/Michael reactions gave spirooxindoles.
View Article and Find Full Text PDFOrg Lett
October 2024
College of Pharmaceutical Sciences, Hebei University, Baoding 071002, China.
Two different cascade pathways to access spirobutenolides were achieved based on the substrate-controlled regioselectivity of deconjugated butenolides. A new class of functional deconjugated butenolides was designed and exhibited superior γ-regioselectivity in the vinylogous Michael/Michael cascade reactions with cinnamaldehydes. The aryl-substituted deconjugated butenolides and cinnamaldehydes underwent a Michael/Michael/aldol/dehydration cascade process induced by double α-regioselectivities.
View Article and Find Full Text PDFOrg Biomol Chem
October 2024
School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland, 1010, New Zealand.
Pallamolide A is a 7,8--labdane terpenoid possessing a unique bicyclo[2.2.2]octane core and a spiro-butenolide moiety.
View Article and Find Full Text PDFChemistry
August 2024
School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan (HY) (TM.
Herein we report that readily available 4-alkenylisocoumarins can be regarded as potent dienolate equivalents. For example, lactol silyl ethers derived from 4-alkenylisocoumarins were selectively converted to the corresponding benzo-homophthalates through a fluoride-induced ring opening step that was followed by a ring closure through a vinylogous intramolecular aldol condensation. Likewise, nucleophilic activation of 4-alkenylisocoumarins directly yields diversely poly-substituted naphthalenes and anthracenes without formation of any regioisomer.
View Article and Find Full Text PDFJ Org Chem
June 2024
Department of Chemistry, National Chung Hsing University, Taichung City 40227, Taiwan, R.O.C.
Two substrate-controlled regiodivergent annulation protocols for 2,3-dioxopyrrolidines with 3-alkylidene oxindoles have been developed, which furnished a series of fused dihydropyrrolidone derivatives in high yields with excellent stereoselectivities. Plausible mechanistic pathways for both annulation reactions are proposed that [3 + 3] annulation reaction involves vinylogous Michael addition followed by intramolecular aldol cyclization, while [4 + 2] annulation reaction occurs through a vinylogous Michael addition and a subsequent intramolecular -Michael cyclization.
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