The first 4-position-selective C-H perfluoroalkylation and perfluoroarylation of six-membered heteroaromatic compounds were achieved using nucleophilic perfluoroalkylation and perfluoroarylation reagents. The regioselectivity was controlled by electrophilically activating the heteroaromatic rings, while sterically hindering the 2-position, with a sterically bulky borane Lewis acid. The reaction proceeded in good yield, even in gram scale, and by a sequential reaction without isolating the intermediates. This reaction could be applied to late-stage trifluoromethylation of a bioactive compound.
Successful benzylic C(sp(3) )-H trifluoromethylation, pentafluoroethylation, and heptafluoropropylation of six-membered heteroaromatic compounds were achieved as the first examples of a practical benzylic C(sp(3) )-H perfluoroalkylation. In these reactions, BF2 Cn F2n+1 (n=1-3) functioned as both a Lewis acid to activate the benzylic position and a Cn F2n+1 (n=1-3) source. The perfluoroalkylation proceeded at both terminal and internal positions of the alkyl chains. Perfluoroalkylated products were obtained in moderate to excellent yields, even on gram scale, and in a sequential procedure without isolation of the intermediates. By using this method, trifluoromethylation of a bioactive compound, as well as introduction of a CF3 group into a bioactive molecular skeleton, proceeded regioselectively.
The synthesis of tofogliflozin (1), a sodium glucose cotransporter 2 (SGLT2) inhibitor, was achieved through the key steps of intramolecular [4 + 2] cycloaddition of dienone-yne intermediate, aerobic aromatization, and anomeric equilibration, thus enabling the construction of a dihydroisobenzofuran moiety of 1. Subsequent hydrogenolysis followed by global deprotection afforded the desired compound 1. The divergent synthesis of the anomer of 1 (15) is also described.
Successful benzylic C(sp 3 ) À Ht rifluoromethylation, pentafluoroethylation, and heptafluoropropylation of sixmembered heteroaromatic compounds were achieved
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