Single electron transfer approaches to the practical synthesis of aromatic and heterocyclic-CF2H derivatives

Synthesis of Selenium Derivatives using Organic Selenocyanates as Masked Selenols: Chemical Reduction with Rongalite as a Simpler Tool to give Nucleophilic Selenides

The chemical reduction within a family of organic selenocyanates, as masked selenols, using reducing agents, such as Rongalite, sodium dithionite, and sodium thiosulfate is investigated. Using Rongalite, the corresponding diselenides were obtained quantitatively and selectively in very good to excellent yields (51-100 %) starting from alkyl, aryl, and benzyl selenocyanates. The scope of the reaction is unaffected by the electronic nature of the substituents. Furthermore, the reducing agent, Rongalite, is compatible with hydrolysable and reducing-sensitive functional groups. Additionally, a simple methodology employing the in-situ generated benzyl selenolate anion (PhCH2Se-) to promote aliphatic nucleophilic substitution, epoxide ring opening, and Michael addition reactions has been developed; thus, extending the structural diversity of the synthesized selenium derivatives.

Why •CF2H is nucleophilic but •CF3 is electrophilic in reactions with heterocycles

Radical substitution is a useful method to functionalize heterocycles, as in the venerable Minisci reaction. Empirically observed regiochemistries indicate that the CF2H radical has a nucleophilic character similar to alkyl radicals, but the CF3 radical is electrophilic. While the difference between •CH3 and •CF3 is well understood, the reason that one and two Fs make little difference but the third has a large effect is puzzling. DFT calculations with M06-2X both reproduce experimental selectivities and also lead to an explanation of this difference. Theoretical methods reveal how the F inductive withdrawal and conjugative donation alter radical properties, but only CF3 becomes decidedly electrophilic toward heterocycles. Here, we show a simple model to explain the radical orbital energy trends and resulting nucleophilicity or electrophilicity of fluorinated radicals.

Nucleophilic Substitution of Selenosulfonates with Me3SiCF2Br: Facile and Efficient Access to Bromodifluoromethylated Selenides under Metal-Free Conditions

A facile synthesis of bromodifluoromethylated selenides under metal-free conditions is described here. Commercially available Me₃SiCF₂Br and bench-stable selenosulfonates react smoothly to give a broad scope of alkyl- and aryl-substituted bromodifluoromethylated selenides in moderate to good yields via a difluorocarbene intermediate. This protocol features a short reaction time, the absence of toxic waste, good scalability, and successful late-stage modification of bioactive molecules. In addition, the title products can be easily converted to different fluorinated and ¹⁸F-labeled selenides.

Synthesis of new quinoxalines containing an oxirane ring by the TDAE strategy and in vitro evaluation in neuroblastoma cell lines

Neuroblastoma is an aggressive pediatric malignancy with significant chemotherapeutic resistance. In order to obtain new compounds active on neuroblastoma cell lines, we investigated the reactivity of carbanion formed via TDAE in quinoxaline series. The new synthesized compounds were tested for their anti-proliferative activity on two neuroblastoma cell lines, and seven oxirane derivatives obtained interesting activities.

Progress in fluoroalkylation of organic compounds via sulfinatodehalogenation initiation system

The sulfinatodehalogenation reaction represents one of the most important methodologies to incorporate fluorine into organic molecules. Using inexpensive sulfur-containing reactants such as Na(2)S(2)O(4) under mild conditions, per- and polyfluoroalkyl halides (R(F)X, X = Br, I, CCl(3)) can be transformed smoothly into the corresponding sulfinate salts. This method is also used for the perfluoroalkylation of alkenes, dienes, alkynes and aromatics. Notably, after 1998, the sulfinatodehalogenation of perfluoroalkyl chlorides (R(F)Cl) has been realized by using dimethylsulfoxide (DMSO) as a solvent instead of CH(3)CN/H(2)O in the Na(2)S(2)O(4)/NaHCO(3) initiation system. Perfluoroalkyl chlorides, ethyl chlorofluoroacetates and chlorodifluoroacetates, and even nonfluorinated compounds, such as ethyl chloro- or dichloroacetates and chloroform, were either converted into the corresponding sulfinate salts or alkylated alkenes, alkynes and aromatics (including porphyrins). The sulfinatodehalogenation reaction has remarkable advantages. With the increasing demands to utilize the unique properties of fluorine and fluorinated functional groups in medicinal, agricultural and material sciences, we believe that there will continue to be useful developments in sulfinatodehalogenation chemistry and it will be applied more widely in the future.

A new reagent for direct difluoromethylation

Molecular scaffolds containing alkylfluorine substituents are desired in many areas of chemical research from materials to pharmaceuticals. Herein, we report the invention of a new reagent (Zn(SO(2)CF(2)H)(2), DFMS) for the innate difluoromethylation of organic substrates via a radical process. This mild, operationally simple, chemoselective, and scalable difluoromethylation method is compatible with a range of nitrogen-containing heteroarene substrates of varying complexity as well as select classes of conjugated π-systems and thiols. Regiochemical comparisons suggest that the CF(2)H radical generated from the new reagent possesses nucleophilic character.

Rongalite®-Promoted Odourless and Highly Regioselective Synthesis of β-Hydroxyselenides under Solvent-Free Conditions

An efficient and facile procedure for the odourless and highly regioselective synthesis of β-hydroxyselenides by the ring-opening of epoxides with 1,2-diphenyldiselenide in the presence of Rongalite® and K2CO3 under solvent-free conditions on grinding has been developed. The important features of this methodology are high yields, reasonably rapid reaction rate, simple workup, high regioselectivity and no requirement for metal catalysts.

Sodium dithionite-promoted synthesis of 2-arylbenzothiazoles by reaction of 2,2'-disulfanediyldianiline with aldehydes in water

Sodium dithionite-promoted synthesis of 2-arylbenzothiazoles by reaction of 2,2'-disulfanediyldianiline with aldehydes in the presence of sodium dodecyl sulfate in water has been developed. Possible reaction pathways are discussed and the effects of different promoter on the reaction are investigated. The important features of this methodology are simple work-up, environmentally benign, high yields, metal-free, and inexpensive reagents.