Hisatomo Mima

Transannular interaction between selenium and sulfur atoms in 5H,7H-dibenzo[b,g][1,5]selenathiocin: Formation of a new heteroatom dication [>Se+−+S<]

Abstract A new medium-sized heterocycles, 5H,7H-dibenzo[ b,g ][1,5]selenathiocin ( 1 ) has been prepared. The transannular interaction between selenium and sulfur atoms in 1 and the formation of dication were found in the reaction of 1 , and its oxides with concd H 2 SO 4 .

Synthesis, crystal structure, and reactivity of new amino- and ammonio-selenuranes containing transannular SeN bond from 5H,7H-dibenzo[b,g][1,5]selenazocines

Abstract The reaction of N-methyl-5H,7H-dibenzo[b,g][1,5]selenazocine Se-oxide 2 with SOCl2 gave the chloroammonioselenurane 3b which was further converted into the methyl- or phenyl- substituted ammonioselenurane (4 or 5) upon treatment with Me2CuLi or Ph2CuLi. The X-ray data of 3b and 4 show that the conformations of 3b and 4 are a twist-boat form. The SeN distances are 2.191 A for 3b and 2.504 A for 4 which are significantly shorter than the sum of the van der Waals radii (3.5 A) of the two elements, indicating transannular bond formation between Se and N. The ClSeN bond angle of 3b and the MeSeN bond angle of 4 are approximately collinear and the other bond angles around the selenium atom are consistent with a pseudo trigonal bipyramidal structure. On the other hand, the reaction of 5H,7H-dibenzo[b,g][1,5]selenazocine 6 with t-BuOCl gave the first aminoselenurane 7 with neutral amino group at the apical position.

Formation, characterization and reactivity of a selenaza dication [R2Se+–N+R3] from N-methyl-5H,7H-dibenzo[b,g][1,5]selenazocine

A new heterocycle containing selenium and nitrogen atoms, N-methyl-5H,7H-dibenzo[b,g][1,5]selenazocine 1, has been synthesized; the reaction of the selenoxide of 1 with (CF3SO2)2O gave a novel selenaza dication salt which was characterized by 77Se NMR spectroscopy, and the dication acts as an oxidizing agent.

Preparation and Structure of New Diazaselenuranes.Transannular Hypervalent Bond between Seleno and Diamino Groups

Abstract The transannular reaction of N-benzyl derivatives of 1,11-(methanoaminomethano)-5H,7H-dibenzo[b,g][1,5]selenazocine (1 and 2) with N-bromosuccinimide (NBS) gave an aminoammonio-selenurane 4 which is the first example of an isolable diazaselenurane with two unsymmetrical apical nitrogen ligands of tertiary amino- and quaternary ammonio-groups. X-ray analysis of the aminoammonioselenurane Br− salt (4a) showed the twin-boat form; the distances of Se…N are 1.918 A and 2.419 A respectively. The structure of selenurane 4 in solution was confirmed by 77Se and 15N NMR spectroscopy using the 15N-enriched aminoammonio-selenurane 4 - 15 N . The apical tertiary amine of selenurane 4 behaves as a nucleophile toward benzylbromide to give the bisammonio-selenurane 5. The aminoammonio and bisammonio-selenuranes 4 and 5 were converted into the neutral amines upon treatment with 2 equiv. of SmI2.

New cyclic dichalcogenonio-selenuranes induced by transannular multichalcogenides participation

Abstract The significant conformational change was found when cyclic chalcogenides, 1,11-(methanoselenomethano)-5H,7H-dibenzo[b,g][1,5]diselenocin (1) and 1,11-(methanothiomethano)-5H,7H-dibenzo[b,g][1,5]selenathiocin (3), were dissolved in concentrated H2SO4; i.e., the twin-chair forms of 1 and 3 in CHCl3 were converted completely into the twin-boat forms of the selenurane dications 2 and 4 in H2SO4. Two-electron oxidation of 1 or 3 with 2 equiv of NOPF6 gave the cyclic selenurane dication 2PF6− salt 2a or 4a with contains two selenonium or two sulfonium cations at the apical positions. The selenurane 2a or 4a could be reduced readily to neutral 1 or 3 upon treatment with PhSH, Ph3P, phenothiazine, or SmI2; that is, 2a or 4a acts as an oxidizing agent.

Formation of Dication and Hypervalent Bond from 5H,7H-Dibenzo[b,g][1,5]Selenazocine

Abstract The reaction of the selenoxide 2 of N-methyl-5H,7H-dibenzo-[b,g][1,5]selenazocine (1) with (CF3SO2)2O gave the selenaza dication salt 3 which acts as an oxidizing agent. A novel σ-selenurane 4 was prepared by either the reaction of selenide 1 with t-BuOCl or the reaction of selenoxide 2 with SOCl2; the crystal structure of 4 shows the chloroammonioselenurane with a distorted trigonal-bipyramidal geometry around the selenium atom.