Pd‐Catalyzed Decarboxylative Asymmetric Protonation of Sterically Hindered α‐Aryl Lactones and Dihydrocoumarins

Pd‐catalyzed decarboxylative asymmetric protonation (DAP) has been developed for sterically hindered α‐aryl lactone and dihydrocoumarin substrates. Optimization studies were conducted using δ‐lactone‐ and dihydrocoumarin‐derived α‐aryl, β‐oxo‐allyl esters with 2,4,6‐trimethoxyphenyl as the aryl subs...

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Bibliographic Details
Published inAdvanced synthesis & catalysis Vol. 360; no. 16; pp. 3138 - 3149
Main Authors James, Jinju, Akula, Ramulu, Guiry, Patrick J.
Format Journal Article
LanguageEnglish
Published Heidelberg Wiley Subscription Services, Inc 17.08.2018
Subjects
Aromatic compounds
Asymmetry
Decarboxylation
Dihydrocoumarins
Enantioselective protonation
Ephedrine
Esters
Lactones
Palladium
Palladium Catalysis
Protonation
Substrates
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Summary:Pd‐catalyzed decarboxylative asymmetric protonation (DAP) has been developed for sterically hindered α‐aryl lactone and dihydrocoumarin substrates. Optimization studies were conducted using δ‐lactone‐ and dihydrocoumarin‐derived α‐aryl, β‐oxo‐allyl esters with 2,4,6‐trimethoxyphenyl as the aryl substituent. In the absence of a chiral P,N‐ligand, (1R,2S)‐(−)ephedrine, a cheap and readily available chiral proton donor, induced enantioselectivities of up to 92% ee and 88% ee with lactone and dihydrocoumarin substrates, respectively. Bulky aryl groups containing di‐ortho substitutions and naphthyl groups gave the highest enantioselectivities of up to 92% and 86%, respectively. A stereochemical rationale is proposed to explain the preferred sense of asymmetric induction.
ISSN:1615-4150
1615-4169
DOI:10.1002/adsc.201800724