Asymmetric Fluorination, Trifluoromethylation, and Perfluoroalkylation Reactions

Organocatalytic Multiple Cascade Reactions: A New Strategy for the Construction of Enantioenriched Tetrahydrocarbazoles

“…Among the catalysts examined, diarylprolinol TMS ether V was identified as the best promoter (Table 1, entry 5 vs. entries 2-4). A dramatic improvement in product yield was achieved using a benzyl instead of a methyl group as the protection group without significant influence on the relative or absolute sense of the stereochemistry ( [10][11][12][13] revealed that CH 3 CN was the optimal solvent (88% yield, 76:24 dr, 94% ee).…”

“…Other halogenated vinylindole substrates can also be utilized in this cascade sequence (Table 2, entries 11 and 12, Figure 1) and, importantly, these products should be valuable intermediates for further functionalizations. [13] Moreover, multi-substituted vinylindole derivatives can readily participate in this reaction and afford various substituted enantioenriched tetrahydrocarbazoles in high yields and excellent stereoselectivities (Table 2, entries 13, 14 and 21). When acrolein was employed, the reaction proceeded smoothly to give the desired product in 90% yield but with only moderate enantiomeric excess ( Table 2, entry 17) which might be due to racemization.…”

Selective fluorination of natural products

“…Podophyllotoxin was fluorinated using NFSI to form 2-fluoropodophylotoxin 173. 25 This potent antitumor agent was obtained by a completely diastereoselective fluorination of the sodium enolate formed with NFSI (Scheme 49).…”

Acid-Base Catalysis of Chiral Pd Complexes: Development of Novel Catalytic Asymmetric Reactions and Their Application to Synthesis of Drug Candidates

“…Thus an efficient method for direct enantioselective construction of fluorinated stereogenic carbon centers is extremely important. 47,48) When we became interested in this work, there had been only two reported examples, where pioneering but limited success was achieved in respect to both substrate-generality and enantioselectivity. 49,50) Electrophilic fluorination reactions of carbonyl compounds, in principle, are accompanied by concomitant generation of a stoichiometric amount of an acidic co-product (Chart 11).…”