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 isomerized to 2,2,4,4-tetramethyl-1,5-diphenyl-8-oxa-6,7-dithiabicyclo[3.2.1]octane probably via 2,2,4,4-tetramethyl-1,5-diphenyl-5-thioxo-1-pentanone S-sulfide.

The reaction of the dihydrazone of 2,2,6,6-tetramethyl-1,7-diphenyl-1,7-dione with Se2Cl2 in refluxing benzene in the presence of tributylamine gave the corresponding 1-oxo-7-selone and 1,7-diselone derivatives in 14 and 33% yields, respectively, while similar reaction of the dihydrazone of 2,2,5,5-tetramethyl-1,6-diphenyl-1,6-dione gave bicyclic 1,3-diselenetane (25%), 1,2,4-triselenolane (20%), and cyclohexene (12%) derivatives by intramolecular cyclizations.

Oxidation of 2,2,3,3-tetramethyl-1,4-diphenyl-5,6-dithiabicyclo[2.1.1]hexane with m-chloroperbenzoic acid gives two isomeric endo- (4a) and exo-sulfoxides (4b), three S,S′-dioxides (endo, exo-5a, exo, exo-5b, and endo, endo-5c), and an S,S,S′-trioxide (6). The relative reactivity to further oxidation is 4b >> 4a and 5b > 5a, which suggests that the attractive 1,3-transannular interaction operative in 1,3-dithietane part of 4a and 5a decreases the reactivity of 4a and 5a. 4b isomerizes to 4a on standing over silica gel at room temperature and also 5b is converted to 5a on heating. Heating 6 in refluxing toluene yields 3,3,4,4-tetramethyl-1,2-diphenylcyclobutene, 2,5-dimethyl-3,4-diphenyl-2,4-hexadiene, and the isomeric trioxide.

The reactions of 2,2,4,4-tetramethyl-1,5-diphenyl-1,5-pentanedione monohydrazone with S2Cl2 and Se2Cl2 gave 2,2,4,4-tetramethyl-1,5-diphenyl-8-oxa-6,7-dithiabicyclo[3.2.1]octane (9) and 2,2,4,4-tetramethyl-1,5-diphenyl-8-oxa-6,7-diselenabicyclo[3.2.1]octane (10), respectively. Dechalcogenation of 9 or 10 with triphenylphosphine in boiling toluene yielded an equilibrium mixture of 2,2,4,4-tetramethyl-1,5-diphenyl-6-oxa-7-thiabicyclo[3.1.1]heptane (11) and 2,2,4,4-tetramethyl-1,5-diphenyl-5-thioxo-1-pentanone (13) or 2,2,4,4-tetramethyl-1,5-diphenyl-6-oxa-7-selenabicyclo[3.1.1]heptane (12), respectively. On the other hand, the reaction of 10 with hexamethylphosphorous triamide [P(NMe2)3] in boiling toluene gave 12, 3-methyl-3-(2,2-dimethyl-3-oxo-3-phenylpropyl)-2-phenylselenetanes (18), 5-benzoyl-3,3,5-trimethy1-2-phenylselenanes (19), 6,6,8,8-tetramethyl-9-phenyl-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-one (20), and 3,3,5,5-tetramethyl-1,2-diphenylcyclopentene (21), while that of 9 afforded 11, 13, 3-(2-benzoyl-2-methylpropyl)-3-methyl-2-phenylthietanes, 20, and 21. The reaction of 12 with P(NMe2)3 also gave 18, 19, 20, and 21. A single-electron transfer mechanism seems to be operative in the reaction of 9 or 10 with P(NMe2)3. Compounds 11 and 13 are in equilibrium with each other at room temperature, while a ring-opening of 12 to 2,2,4,4-tetramethyl-1,5-diphenyl-5-selenoxo-1-pentanone is observed on heating by the UV-vis and 1H NMR spectra.

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