An oxidation system comprising phenyliodine(III) diacetate (PIDA) and iodosobenzene with inorganic bromide, i.e., sodium bromide, in an organic solvent led to the direct introduction of carboxylic acids into benzylic C–H bonds under mild conditions. The unique radical species, generated by the homolytic cleavage of the labile I(III)–Br bond of the in situ-formed bromo-λ3-iodane, initiated benzylic carboxylation with a high degree of selectivity for the secondary benzylic position.
The
synthesis of 2-oxygenated dihydrobenzofurans involving the
[3 + 2] coupling of quinone monoacetals with vinyl ethers has been
realized by tetrabutylammonium triflate catalysis. The reaction involves
a new activation method of the acetal moiety in quinone monoacetals
under acid-free conditions affording the highly oxygenated dihydrobenzofurans.
This new activation mode was achieved by using the triflate anion
catalyst for stabilization of the highly reactive cationic intermediate.
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