Diaryl sulfoxides synthesis

Olah et al.466 observed immediate formation of protonated benzenesulfinic acid upon addition of SO2 to benzenium ion formed in H SO3F-Sb I 5-SO2C11 solution at —78°C. Based upon this observation, Laali and Nagvekar467 developed a method for the synthesis of aromatic sulfoxides [Eq. (5.169)]. Product formation was interpreted in terms of dehydration of protonated benzenesulfinic acid followed by nucleophilic attack by the aromatic to the formed arenesulfinyl cation. Mixed sulfoxides (4-fluorophenyl-4-methylphenyl and 4-fluorophenyl-3-trifluoromethyl sulfoxides) were also prepared by sequential addition of the two aromatics. The direct synthesis of symmetric diaryl sulfoxides in high yields (room temperature, 2—48 h, 50-95%) has been reported through the electrophilic activation of thionyl chloride with triflic acid.468... 

Akhtar et al. [47] described an improved triarylsulfonium salt synthesis by modifying previous P205 based reactions. Use of methanesulfonic acid solvent for the condensation of aromatic compounds with dialkyl or diaryl sulfoxides rapidly produced high yields of sulfonium salt under mild conditions. 

The prochiral sulfoxide diols were dehydrated under asymmetric conditions to yield spirosulfuranes with a rather low enantiomeric excess (below 5%), as described above. Further, Szabd et al. have reported the first stereospecific synthesis of optically active spirosulfuranes as shown in Scheme 31 [69]. Optical active spirosulfuranes 54-57 were prepared by dehydration of the optically active diaryl sulfoxides 58-61, carrying reactive CH2OH and COOH substituents in very high yields. The molecular structures, including the absolute configurations, were determined by X-ray crystallography. 

Andersen later extended this work to include the synthesis of various chiral diaryl sulfoxides via the appropriate arylmagnesium bromide reagents and was also able to provide further evidence to support the proposed inversion of configuration at sulfur as highlighted in Scheme 2.3 [8]. 

The use of THF as solvent with organolithium nucleophiles, as described by Wudl and Lee, resulted in significant reduction in the levels of diastereoselectivity. Entries 7-9 of Table 2.9 highlight the limitations of this procedure for the synthesis of diaryl sulfoxides and therefore dictate that alkyl aryl sulfoxides are synthesized... 

An equimolar amount of 30%-H2O2 added dropwise with stirring to phenyl vinyl sulfide in acetic anhydride, stirring continued 5-6 hrs., and allowed to stand overnight phenyl vinyl sulfoxide. Y 82%. F. e. s. A. V. Sviridova, V. I. Laba, and E. N. Prilezhaeva, Zh. Org. Khim. 7, 2480 (1971) C. A. 76, 72158 with N-chloro-nylon-66 in methanol-benzene or water-dioxane s. Y. Sato, N. Kunieda, and M. Kinoshita, Chem. Lett. 1972, 1023 (Eng) C. A. 77, 164179 with ammonium cerium(IV) nitrate, mostly diaryl sulfoxides, s. T.-L. Ho and C. M. Wong, Synthesis 1972, 561. 

The synthesis of 4,5-diaryl-6-phenylsulfanyl-2,3-benzo-l,3a,6a-triazapentalenes 239 through Pummerer-type reactions of (benzotriazol-l-yl)allylic sulfoxides 238 with trifluoroacetic anhydride in THF has been reported (Equation 35) <2002EJ0493>. Similarly, unstable solid imines 240 treated without purification with trifluoroacetic anhydride (TFAA) provide 241 (Equation 36) <2003TL7507>. 

A simple, efficient synthesis of 4-substituted 1,2,4,6-thiatriazine 1,1-dioxides involves reacting 0,0 -diaryl carbonimidates with thionyl chloride and triethylamine to give sulfoxides which are oxidized with MCPBA. The resulting sulfamides are then reacted with primary amines to give the required products (Scheme 9) <87S170>. 

A general and practical method for synthesis of aryl-substituted five-membered heterocycles was developed. In the presence of KOH (30 mol%), l,4-diaryl-l,3-butadiynes undergo a cyclocondensation reaction with water in dimethyl sulfoxide at 80 °C to afford 2,5-diarylfurans in good-to-exceUent yields (14T8252). 

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