Trifluoromethyl-substituted aromatic compounds were easily synthesized by the oxidative desulfurization-fluorination reaction of readily accessible methyl arenecarbodithioates using [n-Bu4N]H2F3 and 1,3-dibromo-5,5-dimethylhydantoin (DBH) under extremely mild conditions. Use of N-bromosuccinimide or N-iodosuccinimide instead of DBH afforded difluoro(methylthio)methyl-substituted aromatics. In a similar way, 3,3,3-trifluoropropenyl-substituted aromatic compounds were readily prepared from the corresponding α,β-unsaturated carbodithioates.
A series of novel 3-aryl-5-tert-butyl-4-chloro-4-oxazolin-2-ones (16) have been prepared and found to show significant herbicidal activity in the grams per are range against broadleaf and narrowleaf weeds. The key step in the introduction of the chlorine atom at the 4-position of the 4-chloro-4-oxazolin-2-one ring is dichlorination using chlorine gas and subsequent dehydrochlorination using diazabicyclo[5.4.0]undecene. 4-Alkylthio-and 4-methyl-4-oxazolin-2-one rings were synthesized from R-substituted R-bromopinacolone by cyclization reaction. Among the synthesized compounds, 5-tertbutyl-4-chloro-3-[4-chloro-2-fluoro-5-(2-propynyloxy)phenyl]-4-oxazolin-2-one (16h) showed the greatest activity against several weeds without damage to transplanted rice in the paddy field.
Upon treatment with n-Bu4NH2F3 and 1,3-dibromo-5,5-dimethylhydantoin, various organic sulfides underwent a Pummerer-type rearrangement, followed by fluorination, to give α-fluoro sulfides. The fluoro-Pummerer rearrangement, when applied to RCH(SMe)CF2SMe, gave trifluoro sulfides RCF(SMe)CF2SMe. When an HF-pyridine reagent was used as the fluorinating agent, an oxidative desulfurization–fluorination reaction occurred depending on the structure of the substrates.
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