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The reaction of the 6-exo-oxide of 2,2,4,4-tetramethyl-1,5-diphenyl-6,7-dithiabicyclo[3.1.1]heptane (2) with 2KHSO5·KHSO4·K2SO4 gave the first isolable dithiirane oxide, (1RS, 3SR)-3-phenyl-3-(1,1,3,3-tetramethyl-4-oxo-4-phenylbutyl)dithiirane 1-oxide (1), while the 6-endo-oxide of 2 gave both 1 and its (1RS, 3RS)-isomer 10. Under similar reaction conditions, 2 yielded the first isolable, unoxidized dithiirane, 3-phenyl-3-(1,1,3,3-tetramethyl-4-oxo-4-phenylbutyl)dithiirane (3). The dithiirane 3 was also obtained by treatment of 2 with NaOCl–NaClO4. The X-ray structure analyses were performed for 1, 3, and 10. Treatment of unsymmetrical 8,8-dimethyl-1,9-diphenyl-10,11-dithiatricyclo[7.1.1.02,7]undeca-2,4,6-triene with NaOCl–NaClO4gave 3-[1-(o-benzoylphenyl)-1-methylethyl]-3-phenyldithiirane selectively in good yield. However, 1,3-dithietanes, prepared from adamantane-2-thiones, failed to give the corresponding dithiiranes by treatment with 2KHSO5·KHSO4·K2SO4 or NaOCl–NaClO4. The dithiirane 3 thermally isom...

Optical resolution of (1RS, 3SR)-(1) and (1RS, 3RS)-(2) dithiirane 1-oxides was achieved by HPLC equipped with a chiral column to give 1a and 1b and 2a and 2b, respectively. X-ray analyses proved absolute configurations of 1a and 1b to be (1R, 3S) and (1S, 3R), while those of 2a and 2b were determined to be (1R, 3R) and (1S, 3S), respectively, since 2a and 2b isomerized stereospecifically to 1b and 1a, respectively. Enantiomeric dithiirane 1-oxides 1a and 1b reacemized to each other whereas 2a and 2b did not. To the racemization (oxygen migration) is proposed a mechanism involving homolysis of the S(O) S bond at the initial step followed by a ring closure giving a 1,2,4-oxathietane intermediate. Isomerization between 1 and 2 was inhibited by a radical scavenger, DPPH.

2-Methoxyallenylmethylsilane reacts with alkenes and alkynes in a [2+2] cycloaddition mode to give cyclobutanes and cyclobutenes, respectively. Cycloadducts are converted to di-exo-methylene compounds through 1,2-elimination of the methoxy and silyl groups. These di-exo-methylenecyclobutanes and -cyclobutenes react with alkenes and 1,3-dienes to afford fused bi- and tricyclic compounds.