Dimethylphenacylsulfonium bromide

As a final example of regioselective control (Scheme 25), sulfonium ylides usually give nitrones when reacted with nitroso groups via oxaziridine intermediates. However, 7-aryl-2-dimethylamino-3,4,5,6-tetrahydropteridine-4,6-diones 120 were directly formed when nitrosopyrimidine 121 reacted with dimethylphenacylsulfonium bromides 122 instead of the isomeric 5-oxides <1996H(43)437>. It was also reported that the resulting pteridines were reduced to give 7,8-dihydro derivatives 123 with sodium dithionite (Table 7). 

Acyl and perfluoroalkyl diazomethanes react with nitrogen oxides, and a-diazosulfones with nitrosyl chloride or dinitrogen trioxide, to give furoxans. The process is believed to involve nitrosation, followed by loss of nitrogen to form the nitrile oxide which subsequently dimerizes. Nitrosation of dimethylphenacylsulfonium bromide with nitric acid/sodium nitrite gives dibenzoylfuroxan. 

Diphenylfuroxan is formed from the silver salt of phenylnitrosolic acid with iodine.251 Nitrosation of dimethylphenacylsulfonium bromide (HN03/ NaN02) gives dibenzoylfuroxan.252 With boron trifluoride etherate in... 

Bohme and Krause312 describe the preparation of various dialkylphenacylsulfonium salts, e.g., dimethylphenacylsulfonium bromide co-Bromoacetophenone (9 g) is dissolved in a mixture of water (1 volume) and acetone (20 volumes), and dimethyl sulfide (3 g) is added. After about 0.5 h the sulfonium salt separates as long, colorless needles, m.p. 145° (10.2 g, 85 %). 

Dimethylphenacylsulfonium bromide and CuBr in acetonitrile heated at 75-80° complex (Y 93%) allowed to react 40 min. at room temp, with 2 equivalents ethyl diazoacetate in acetonitrile product (Y 65%). F. e. s. T. Sato and J. Higudii, Tetrah. Let. 1972, 407. 

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