Shigenobu Aoyagi

Novel generation and ring closure of 1,3-thiaza-1,3-butadiene S-oxides through thermal cycloreversion of 6H-1,3,5-oxathiazine S-oxides

Heating of 6H-1,3,5-oxathiazine S-oxides efficiently afforded 1,2,4-oxathiazoles through the mechanism involving thermal cycloreversion of the substrates and the subsequent ring closure of the intermediary 1,3-thiaza-1,3-butadiene S-oxides.

Pummerer-type α-functionalization of arylseleninylacetates by treating with trimethylsilyl- or tri-n-butylstannyl-masked nucleophiles and trifluoroacetic anhydride or a Lewis acid

Abstract Arylseleninylacetates underwent facile α-functionalization on treatment with trimethylsilyl- or tri- n -butylstannyl-masked nucleophiles and trifluoroacetic anhydride (TFAA) or a Lewis acid.

Regioselective monohalogenation of 3,3-disubstituted bornane-2-thiones via thione–dihalogen complexes

Abstract Reaction of 3,3-disubstituted bornane-2-thiones with Br2, ICl, or Cl2 afforded the corresponding 10-bromobornane-2-thiones, 10-iodobornane-2-thiones, or the products originated from skeletal rearrangement of 10-chlorobornane-2-thiones, respectively.

1,8-DIMETHYL-1,8-DIHALO-1,8-DIGERMACYCLOTETRADECANES. THE FIRST GERMAMACROCYCLES WITH ANION TRANSPORT CAPABILITY

It has been shown that 1,8-dichloro-1,8-dimethyl-1,8-digermacyclotetradecane transports chloride anion more effectively than bromide anion in a U-tube test. The dibromo analogue also can transport anions. The efficiency of transport of open chain analogues with a similar environment around germanium is inferior to that of cyclic systems which confirms the essential role of the ring structure for anion transport. The anion transport capability was examined for other germanium-containing 14-membered rings. A possible mechanism for anion transport is proposed.

Nuclear magnetic resonance spectra of organogermanium compounds. Part 11. Synthesis and nuclear magnetic resonance spectra of tetramethyldigerma- and octamethyltetragerma-cycloalkanes

Digermamacrocycles ranging from 10- to 22-membered rings and tetragermamacrocycles ranging from 20- to 44-membered rings have been prepared and their 13C and 73Ge NMR spectra determined. A preliminary experiment indicates that the germamacrocycles possess no anion transfer properties.

Molecular structure of 1,1,8,8-tetramethyl-1,8-digermacyclotetradecane: the first 14-membered germacycles

An X-ray crystallographic analysis indicated that 1,1,8,8-tetramethyl-1,8-digermacyclotetradecane exists exclusively as the [3434] conformer with germanium atoms at corner sites in the crystalline state. Molecular mechanics calculations (MM2) of 1,8-digermacyclotetradecane and germacyclohexanes showed that small C–Ge–C bond angle and C–Ge–C–C dihedral angle are characteristic of germacycles ranging from 14-membered to 6-membered rings. This tendency is also expected for the acyclic system when the C–Ge–C–C moiety is in the gauche conformation.

Oxidation of sterically-crowded selones using chloramine-T: generation and skeletal rearrangement of selone Se-imides

Abstract Treatment of sterically-crowded bornane-2-selones possessing substituted bornane skeletons with chloramine-T afforded several products originated from intermediary selone Se -imides, and the direct observation of the intermediates was performed by NMR monitoring at low temperature.

1,12-Digermacyclodocosanes. Synthesis, structure and anion transport capability

An X-ray crystallographic analysis indicated that 1,1,12,12-tetramethyl-1,12-digermacyclodocosane exists exclusively as the [3838] conformer with germanium atoms at corner sites in the crystalline state. The geometric parameters of this compound are nicely reproduced by MM3 calculations and are found to be comparable with those of relevant carbocycles. The anion transport capability of 1,12-dichloro-1,12-dimethyl-1,12-digermacyclodocosane is much the same with that of the 14-membered-ring analogue.

Novel Thiofomylation of Primary and Secondary Amines Using N-Aryl-1,2,3,4,5,7-Pentathiazocanes

Heating of N-aryl-1,2,3,4,5,7-pentathiazocanes 1 in the presence of primary and secondary amines afforded N-Alkyl or N,N-dialkylthioformamides 5, and similar heating of 1 in the absence of amines afforded an inseparable mixture of acyclic polysulfides 4 bearing a thioformanilide moiety on each terminal. Bisthioformanilides 4 were also converted into 5 by treating with these amines, and the thioformylation was assumed to proceed through a pathway involving the ring fission of 1 and the subsequent nucleophilic attack of these amines onto the thioformyl group of 4.