A novel approach for the formation of anomeric carbon-functionalized furanoside systems was accomplished through the employment of an oxo-rhenium catalyst. The transformation boasts a broad range of nucleophiles including allylsilanes, enol ethers, and aromatics in addition to sulfur, nitrogen, and hydride donors, able to react with an oxocarbenium ion intermediate derived from furanosidic structures. The excellent stereoselectivities observed followed the Woerpel model, ultimately providing 1,3- cis -1,4- trans systems. In the case of electron-rich aromatic nucleophiles, an equilibration occurs at the anomeric center with the selective formation of 1,3- trans -1,4- cis systems. This anomalous result was rationalized through density functional theory calculations. Different oxocarbenium ions such as those derived from dihydroisobenzofuran, pyrrolidine, and oxazolidine heterocycles can also be used as a substrate for the oxo-Re-mediated allylation reaction.

Iron porphyrin methoxy complexes, of the general formula [Fe(porphyrin)(OCH 3 )], are able to catalyze the reaction of diazo compounds with alkenes to give cyclopropane products with very high efficiency and selectivity. The overall mechanism of these reactions was thoroughly investigated with the aid of a computational approach based on density functional theory calculations. The energy profile for the processes catalyzed by the oxidized [Fe III (Por)(OCH 3 )] (Por = porphine) as well as the reduced [Fe II (Por)(OCH 3 )] − forms of the iron porphyrin was determined. The main reaction step is the same in both of the cases, that is, the one leading to the terminal -carbene intermediate [Fe(Por)(OCH 3 )(CHCO 2 Et)] with simultaneous dinitrogen loss; however, the reduced species performs much better than the oxidized one. Contrarily to the iron(III) profile in which the carbene intermediate is directly obtained from the starting reactant complex, the favored iron(II) process is more intricate. The initially formed reactant adduct between [Fe II (Por)(OCH 3 )] − and ethyl diazoacetate ( EDA ) is converted into a closer reactant adduct, which is in turn converted into the terminal iron porphyrin carbene [Fe(Por)(OCH 3 )(CHCO 2 Et)] − . The two corresponding transition states are almost isoenergetic, thus raising the question of whether the rate-determining step corresponds to dinitrogen loss or to the previous structural and electronic rearrangement. The ethylene addition to the terminal carbene is a downhill process, which, on the open-shell singlet surface, presents a defined but probably short-living diradicaloid intermediate, though other spin-state surfaces do not show this intermediate allowing a direct access to the cyclopropane product. For the crucial stationary points, the more complex catalyst [Fe( 2 )(OCH 3 )], in which a sterically hindered chiral bulk is mounted onto the porphyrin, was investigated. The corresponding computational data disclose the very significant effect of the porphyrin skeleton on the reaction energy profile. Though the geometrical features around the reactive core of the system remain unchanged, the energy barriers become much lower, thus revealing the profound effects that can be exerted by the three-dimensional organic scaffold surrounding the reaction site.

A silver(I) catalyzed regioselective trifluoromethylation of allenes using Langlois's salt (NaOSOCF3) is demonstrated. This transformation enables direct expedient access to α‐trifluoromethylated acroleins, which are valuable synthons for a number of pharmaceuticals and agrochemicals containing vinyl‐CF3 moieties. Versatility of this trifluoromethylation method has been established with good yield and excellent regioselectivity. Preliminary experiments and computational studies were carried out to elucidate the mechanistic insight of this protocol.

A regioselective meta-C–H activation strategy for benzophenone was successfully developed by overriding the inherent ketone-directed ortho-selectivity.

Properly substituted tetrahydrofuran (THF) rings are important building blocks in the synthesis of many natural metabolites. Having reliable procedures to control the stereoselectivity at the THF core while decorating it with different substituents is a fundamental requirement to achieve and fulfill the complexity of nature. We recently reported a new chemical approach to control the stereochemistry in the alkylation and arylation of furanoside derivatives by using a rhenium(V) complex to form an intermediate oxo-carbenium species able to react with proper soft nucleophiles. Here, we describe theoretical calculations, performed at the DFT B3LYP level, to disclose the important mechanistic features which regulate the entire catalytic cycle of the reaction of mono- and disubstituted furanosides with allyltrimethylsilane catalyzed by Re(O)Cl 3 (OPPh 3 )(Me 2 S). Moreover, the key factors governing the allylation step were investigated, confirming that the stereoselectivity, which is independent of the anomeric configuration of starting acetal, mainly arises from the orientation of the substituent at C-4, with only marginal contribution of the substituent at C-5. Finally, puckering Cremer–Pople parameters were used to take trace of the structural modifications throughout the catalytic cycle.