Masaru Hojo

Convenient and Selective Synthesis of 4-Trifluoromethylimidazoles

Thermally induced cyclization of 3-aryl-1,1,1- trifluoropropane-2,3-dione 2-dimethylhydrazones (5) which can be readily prepared from corresponding arenecarbaldehydes afforded selectively the title compounds (3) in high yields without formation of the regioisomers

A Convenient Synthesis of 5-Trifluoromethyl-3-thiazolines and 5-Trifluoromethyl-2,3,4,5-tetrahydro-1,2,4-triazines

5-Trifluoromethyl-3-thiazolines (3) and 5-trifluoromethyl-2,3,4,5-tetra- hydro-1,2,4-triazine (5) were conveniently synthesized from 3-(N-tert- butyl-N-methylhydrazono)-1,1,1-trifluoroalkan-2-ones (1) with the use of silica gel as an effective catalyst. 5-Trifluoromethylimidazole (6) was also obtained in good yield from (1)

Convenient synthesis of 5-trifluoromethyl-3-oxazolines and 5-trifluoromethyloxazoles

Aldehyde tert-butyl(methyl)hydrazones were acylated with trifluoroacetic anhydride to afford 3-tert-butyl(methyl)hydrazono-1,1,1-trifluoroalkan-2-ones in good yields. Several 5-hydroxy-5-trifluoromethyl-3-oxazolines were successfully synthesized by thermally induced reaction of 4 adsorbed on silica gel. Treatment of 5 with POCl 3 /pyridine and subsequent dehydrochlorination with diisopropylethylamine gave 5-trifluoromethyloxazoles in high yields

A convenient synthesis of 2-pyrazolines and pyrazoles from aldehyde hydrazones and ethyl propiolate

Aldehyde methylhydrazones (3) reacted with ethyl propiolate in the presence of acetic acid affording 4-ethoxycarbonyl-1-methyl- 2-pyrazolines (4) in 13-44% yields. Easily (4) was dehydrated to the corresponding 4-ethoxycarbonyl-1-methylpyrazoles (6) by treatment with H 2 O 2 in the presence of FeCl 2

Convenient Synthetic Method for 5-Trifluoromethyloxazoles and 5-Trifluoromethylthiazoles

5-(Trifluoromethyl)oxazoles (3) and 5-(trifluoromethyl)thiazoles (4) were conveniently as well as effectively synthesized from 3-(N-tert-butyl-N-methylhydrazono)-1,1,1-trifluoroalkan-2-ones (1) via 5-(trifluoromethyl)-3-oxazoline (2). One-pot conversion of 1 to 4 also proceeded successfully

Oxidative cyclization of trifluoroacetylated aldehyde dimethylhydrazones : a new convenient synthesis of trifluoromethylated oxadiazine derivatives

Trifluoromethylated oxadiazine derivatives (3) were conveniently synthesized by NaIO 4 -mediated cyclization of hydrazones (1) which are readily obtained by trifluoroacetylation of aldehyde dimethylhydrazones

A Facile Synthesis of Fluorine-containing Bicyclic Oxadiazines

By treatment with trifluoroacetic acid fluorine-containing bicyclic oxadiazines (3) could be synthesized in satisfactory yields from hydrazones (1) which were prepared from aldehyde methylhydrazones bearing N-allylic group and trifluoroacetic anhydride