Takabumi Nagai

Reactions of trifluoromethyl ketones. IX. Investigation of the steric effect of a trifluoromethyl group based on the stereochemistry on the dehydration of trifluoromethyl homoallyl alcohols

Abstract In a previous paper we reported that a trifluoromethyl group behaves as a larger substituent than a butyl or a phenyl group and slightly larger than a sec-butyl group in ene reactions of trifluoromethyl carbonyl compounds. Dehydration of trifluoromethyl homoallyl alcohols, which are obtained by the ene reaction of trifluoromethyl ketones, has now been extensively investigated to compare further the steric effect of a trifluoromethyl group with those of other substituents. A trifluoromethyl group behaves as a substituent as large as a cyclohexyl group and a little smaller than a sec-butyl group. Differences between steric effects in the ene reaction and in the dehydration are discussed.

Trifluoromethylation of Tocopherols

Abstract γ- and δ-Tocopherol were converted to iodo compounds, which were trifluoromethylated with trifluoromethyl iodide and copper powder in HMPA.

Diels-Alder reactions of trifluoromethyl dienes obtained from ene reactions of trifluoromethyl carbonyl compounds☆

Abstract The ene reactions of trifluoromethyl carbonyl compounds give products which may be dehydrated to trifluoromethyl dienes; the Diels Alder reaction of these have been investigated. The dienes from trifluoromethyl ketones hardly reacted, probably because the steric effect of the trifluoromethyl group prevents the diene from taking up a cisoid form. Dienes obtained from the ene reaction of trifluoroacetaldehyde have one substituent at a terminal position and react with dienophiles to give trifluoromethylated cyclohexene derivatives.

Synthesis of Fluorine Analogues of Protoporphyrin

Abstract With intention of obtaining a porphyrin derivative useful for diagnosis and therapy of cancer, fluorine analogues of protoporphyrin, in which the vinyl group(s) were replaced by difluorovinyl group(s), were synthesized by the reaction of the formylporphyrins with sodium chlorodifluoroacetate in the presence of triphenylphosphine.

Synthesis of trifluoromethylated tetrahydropyrans from ene reaction products of trifluoromethyl ketones: synthesis of fluorine analogues of sesquiterpenes

Abstract Ene reaction of trifluoromethyl ketones were investigated extensively, 1) and the ene reaction products were transformed to many types of trifluoromethyl compounds. 2) Among these research, the ene reaction products of trifluoromethyl ketones were converted to α-trifluoromethylated tetrahydrofurans. In this study, derivatization of the ene reaction products to α-trifluoromethylated tetrahydropyrans were accomplished. Therefore, treatment of esters of 3,4-unsaturated alcohols with trifluoromethyl ketones gave α-(trifluoromethyl)homoallyl alcohol derivatives, which were hydrolyzed to 2,3-unsaturated 1,5-diol compounds. These were oxidized to δ-ketoalcohols. Hydrogenation of these alcohols, followed by treatment with Grignard reagents, gave trifluoromethylated 1,5-diols, which were dehydrated and cyclized to α- trifluoromethylated tetrahydropyran derivatives, some of which are fluorine analogues of curcumene ether, a sesquiterpene.