RESUMEN
A formal [4 + 2] cycloaddition of N-tosylhydrazones with ortho-quinone methides was developed, affording the facile synthesis of diverse 1,3-oxazine derivatives under mild conditions. In this transformation, N-tosylhydrazones are used as a 1,2-dipole synthon under base-free conditions. Moreover, the substrate scope is broad, and the products are formed with high diastereoselectivities in most of the cases.
RESUMEN
A novel method for site-selective C-H functionalization of ethyl acetate mediated by pyridine-boryl radicals is presented, delivering a variety of 4-phenylbut-3-yn-2-yl acetate derivatives under mild conditions. A distinguishing feature of this reaction is that the pyridine-ligated boryl radicals can abstract the inactive α-hydrogen of the alkoxyl group instead of the α-hydrogen of carbonyl groups described in a previous report using amine-ligated boryl radicals. Significantly, substrates with halogen atoms are compatible under the reaction conditions.
RESUMEN
A challenging deoxygenation of alkoxyl radicals from readily accessible alcohol derivatives was developed, affording facile synthesis of functionalized alkenes with good functional group tolerance under mild reaction conditions. Because alkoxyl radicals can easily undergo ß-fragmentations or hydrogen abstractions, this new strategy for deoxygenation of alkoxyl radicals is highly valuable. Moreover, mechanistic studies revealed that the electron-neutral phosphine acts as the deoxygenation reagent.
RESUMEN
A boryl radical-triggered C-H functionalization of aliphatic ethers/amines or DMF with isocyanides is developed to deliver diverse phenanthridine derivatives in good to excellent yields. The substrate scope is broad, and a wide range of functional groups are tolerated under the standard conditions. The rapid removal of HBPin species by 4-cyanopyridine 1-oxide provides the driving force for this reaction. This new method should make boryl radicals widely applicable in organic synthesis.
RESUMEN
A convenient and efficient method for the construction of aryl trifluoromethyl selenoethers from the corresponding aryl halides in the presence of Ni(COD)2 and an appropriate ligand is reported. Various aryl iodides, bromides, and chlorides were smoothly converted in this reaction by simply varying the ligand, which afforded aryl and heteroaryl trifluoromethyl selenoethers in good to almost quantitative yields. The reaction was also applicable to the synthesis of druglike molecules. This work is the first report for trifluoromethylselenolation of aryl chlorides. Advantages of the present Ni-catalyzed approach include mild reaction conditions, good functional group tolerance, inexpensive reagents, easy operation, and no use of additional additives. This protocol allows for a straightforward and reliable access to trifluoromethyl selenides that are latent screening candidates for new pharmaceuticals and agrochemicals.
RESUMEN
Trifluoromethylthiolation and trifluoromethylselenolation of alkynyl(phenyl)iodonium tosylates by [XCF3]- (X = S, Se) ions was accomplished in 5-10 minutes at room temperature under a N2 atmosphere and provided a variety of alkynyl trifluoromethyl sulfides and selenides in good yields. Compared to the known methods, this approach has several advantages such as short reaction times and metal- and additive-free conditions without needing excess [Me4N][XCF3] reagents. Moreover, the less efficient reactions of (phenylethynyl)benziodoxol(on)e with [Me4N][XCF3] under the standard conditions demonstrate that acyclic alkynyl(phenyl)iodoniums are more powerful alkynyl sources in the conversion. This protocol allows for a fast and convenient access to numerous alkynyl trifluoromethyl sulfides and selenides.
RESUMEN
Silver-mediated direct trifluoromethoxylation of α-diazo esters and ketosteroid was disclosed. The reactions of alkyl α-diazo arylacetates with AgOCF3 or CF3SO2OCF3/AgF at -30 to 10 °C under a N2 atmosphere provided α-trifluoromethoxyl arylacetates in up to 90% yield, while alkyl α-diazo vinylacetates reacting with CF3SO2OCF3/AgF or AgOCF3 afforded γ-trifluoromethoxyl α,ß-unsaturated esters in up to 94% yield. The α-diazo ketosteroid was also trifluoromethoxylated under the standard reaction conditions. This protocol allows for an effective and convenient access to a large number of synthetic building blocks, which are promising in the development of new functional OCF3-molecules.
RESUMEN
Construction of difluoromethylthioethers (2) and difluorobis(arylthio)methanes (3) from RSX (X = SR, Cl, SO2Ph) and TMSCF2H in the absence of transition metals has been explored. The reaction is dramatically influenced by the nature of the base and the molar ratio of the reactants. Reactions between RSX and TMSCF2H in the presence of CsF provided 2 in good yields, whereas the reaction of RSX with TMSCF2H in the presence of t-BuOK afforded 3 in good yields. These protocols allow for convenient and efficient access to both difluoromethylthioethers and difluorobis(arylthio)methanes.