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Studies on Reactions of Thioketones with Trimethyl(trifluoromethyl)silane Catalyzed by Fluoride Ions
Author(s) -
Mlostoń Grzegorz,
Prakash G. K. Surya,
Olah George A.,
Heimgartner Heinz
Publication year - 2002
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(200206)85:6<1644::aid-hlca1644>3.0.co;2-8
Subject(s) - chemistry , trifluoromethyl , medicinal chemistry , fluoride , trimethylsilyl , nucleophile , ring (chemistry) , silylation , derivative (finance) , adduct , sulfide , catalysis , organic chemistry , inorganic chemistry , alkyl , financial economics , economics
Treatment of 2,2,4,4‐tetramethylcyclobutane‐1,3‐dione ( 6 ) in THF with CF 3 SiMe 3 in the presence of tetrabutylammonium fluoride (TBAF) yielded the corresponding 3‐(trifluoromethyl)‐3‐[(trimethylsilyl)oxy]cyclobutanone 7 ( Scheme 1 ) via nucleophilic addition of a CF anion at the CO group and subsequent silylation of the alcoholate. Under similar conditions, the ‘monothione' 1 reacted to give thietane derivative 8 ( Scheme 2 ), whereas in the case of ‘dithione' 2 only the dispirodithietane 9 , the dimer of 2 , was formed ( Scheme 3 ). A conceivable mechanism for the formation of 8 is the ring opening of the primarily formed CF 3 adduct A followed by ring closure via the S‐atom ( Scheme 2 ). In the case of thiobenzophenones 4 , complex mixtures of products were obtained including diarylmethyl trifluoromethyl sulfide 10 and 1,1‐diaryl‐2,2‐difluoroethene 11 ( Scheme 4 ). Obviously, competing thiophilic and carbophilic addition of the CF anion took place. The reaction with 9 H ‐fluorene‐9‐thione ( 5 ) yielded only 9,9′‐bifluorenylidene ( 14 ; Scheme 6 ); this product was also formed when 5 was treated with TBAF alone. Treatment of 4a with TBAF in THF gave dibenzhydryl disulfide ( 15 ; Scheme 7 ), whereas, under similar conditions, 1 yielded the 3‐oxopentanedithioate 17 ( Scheme 9 ). The reaction of dithione 2 with TBAF led to the isomeric dithiolactone 16 ( Scheme 8 ), and 3 was transformed into 1,2,4‐trithiolane 18 ( Scheme 10 ).