COMMUNICATIONScation. Elemental analysis and FAB mass spectrometry established the composition as C,oH5,0,,, consistent with a peroxide. The structure of 7 b was determined by 'HNMR spectroscopy. Para attachment is indicated by the presence of the methine and olefinic protons giving the pattern characteristic of an AABB'C spin system. This spectrum, in contrast to that of 6b, results from a symmetric or Heintschel peroxide; the radical l c undoubtedly forms a compound in which the dioxygen bridge joins para positions.Like the Jacobson dimer of triarylmethyl radicals, Jacobson and Heintschel peroxides, the common oxidation products in a variety of triarylmethyl radical studies, have escaped the attention of chemists for generations. These structures raise a concern : Why are not all bis(triarylmethy1)peroxides methyl-paracoupled in a Jacobson configuration? It previously has been shown that large radicals such as the tert-butoxy radical prefer to attach to para positions of triarylmethyls.[221 Such behavior has not been observed for oxygen. But since the first formed peroxy radical (a large radical by most standards) must attach to the second triarylmethyl radical we always might expect attack at the less hindered para site. Experiments are in progress to determine the first position bound in the formation of 6b. Experimental ProcedureBis(2,6-dimethoxyphenyl)phenylniethanol (1 b-OH): A solution of 1.3-dimethoxyphenyllithium was prepared by addition of 2.5 M nBuLi (34.8 mL, 86.9 mmol) in n-hexane to a solution of 1,3-dimethoxybenrene (10 g, 72.4 mmol) in anhydrous diethyl ether at -78 'C. The mixture was stirred at room temperature under argon for 48 h. Methylbenroate (3.13 g. 23.0 mmol) in benzene (20 mL) was added. and the reaction solution was heated at reflux for 3 days under argon. The reaction mixture was poured into 200 mL of water, and the organic layer was dried and concentrated to yield the methanol as an oil. The oil was crystallized in CH,CI, and hexane.Mp104"C,46%yield. 'HNMR(CDC1,,299.95 MHz):b = 3.38(s,12H), 6.43 (s. 1 H), 6.54(d. J = 8 Hr,4H), 7.11 (t. J = 8 Hz, 2H), 7.13 (m. 1H). 7.21 (m. 2H), 7.46 (m. Telefax: Int. code + (48)858-3698 Dr. M. Shiro Rigaku Corporation (Japan) Angeii-. Chem. h t . Ed. EngI. 1994. 33, No. 7 g ; VCH Verlugsgesrlkhafi mhH. 0-69451 Weinheim, f994 0570-0833/94/0707-0777 i % 10.00t .25/0 $: ' VCH Verlaggerellschufi mbH.

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.

Ph3P (1.3 quiv) 4 * 6 + Ph,P=S c w 3 2 , r . 1 . 79%(6,44)

Dithiirane galten bislang als instabil und wurden nur als nicht faßbare Zwischenstufen diskutiert. Das Dithiiran 1 hingegen läß sich bequem isolieren, reinigen, spektroskopisch und röntgenographisch sowie durch eine Reihe von chemischen Reaktionen charakterisieren.magnified image

The First Isolable Dithiirane (II) by Oxidation of a Dithietane.-For the thermal, solvent-dependent isomerization of (II) to give (III), the thiocarbonyl S-sulfide (VI) is proposed as intermediate. The structure of (II) is determined by X-ray analysis (space group P1 with Z = 2). -(ISHII, A.; AKAZAWA, T.; MARUTA, T.; NAKAYAMA, J.; HOSHINO, M.; SHIRO, M.; Angew. Chem. 106 (1994) 7, 829-830; Dep. Chem., Fac. Sci.,