Carbocyclic functionalization of quinoxalines, their chalcogen congeners 2,1,3-benzothia/selenadiazoles, and related 1,2-diaminobenzenes based on nucleophilic substitution of fluorine

Chalcogen Bonding “2S–2N Squares” versus Competing Interactions: Exploring the Recognition Properties of Sulfur

“…The tail–tail contacts are maintained in the dichloro‐derivative 5 c , where the Cl ⋅⋅⋅ Cl distance is 3.57 Å (sum of van der Waals radii for (Cl+Cl): 3.50 Å). Interestingly, the monomers further arrange to position the sulfur between the two chlorines of the next monomer's tail at 3.63/3.67 Å. Sulfur can similarly interact between two oxygen atoms at close range (3.15 Å), as observed in 9 a (Figure S12) …”

“…Fluorination : Distinct from the derivatives bearing higher halogen substituents, highly aligned squares are abundant for most of the fluoro‐benzothiadiazoles ( 5 b , 7 , 8 , 9 b – 9 e ) . These interactions coexist with the congregation of tightly‐packed F ⋅⋅⋅ F bands, as described for 5 b above (Figure ), which are often at sub‐van der Waals distance (Table S5).…”

Electrochemical reduction, radical anions, and dehalogenation of fluorinated/chlorinated 2,1,3-benzothia/selenadiazoles

“…Most of the studied compounds are known ones. 29,30 Derivatives 1, 2 and 4-9 were prepared by nucleophilic substitution of fluorine in 4,5,6,7-tetrafluoro-2,1,3-benzothiadizole 3, and 10, 11 and 13-19 in 4,5,6,7-tetrafluoro-2,1,3-benzoselenadiazole 12. ECR peak potentials, CVs and some transformations of 1-20 under ECR in DMF in the potential range 0 > E > −2.2 V (vs. saturated calomel electrode, SCE) are represented in Table 1, Figures 2 and 3 (ESI: Figures S1 and S2, Table S1), and Schemes 1 and 2; for ECR of 3 in MeCN, see ref.…”

“…Altogether, these suggest that defluorination of 12 occurs regioselectively at equivalent positions 5 / 6 not involving the positions 4 / 7 (note that in fluorinated selenadiazoles the positions 5 and 6 are much more active in nucleophilic substitution than the positions 4 and 7). 29 This is, however, only minor process because peaks 4C and 4A are characterized by substantially lower currents as compared with the first peaks in CVs ( Figure 3). …”

“…Recently, our group suggested unified synthetic approach to fluorinated 2,1,3-benzothia/selenadiazoles. 29,30 Since redox properties of compounds are of general significance for organic chemistry and its applications, 31 in this work we report on electrochemical reduction (ECR) of new fluorinated 2,1,3-benzothia/selenadiazoles bearing also chlorine and some other substituents (1-20, Figure 1), studied by cyclic voltammetry (CV), as well as on their persistent RAs characterized by EPR spectroscopy and DFT calculations. Compounds 3 and 12 together with their RAs have been characterized earlier 2 as well as related fluorinated 1,4-benzodiazines (quinoxalines) and their RAs.…”