Abstract: A (perfluoroalkyl)dibenzonium salt represented by the following general formula ##STR1## wherein R.sub.f represents a perfluoroalkyl group having 1 to 10 carbon atoms, A represents a sulfur of selenium atom, R.sup.1 and R.sup.2, independently from each other, represent a hydrogen atom or a nitro group, X.sup..crclbar. represents a conjugated base of Bronsted acid, and n is 0 or 1.The said compound is useful as a reagent for introducing a perfluoroalkyl group.

Abstract: A pyridine-compound is reacted with fluorine together with a Bronsted acid-compound or Lewis acid to form a N-fluoropyridinium salt which is very active to other compounds but is very selective for the preparation of a desired product and this product is very useful for a fluorine-introducing agent which makes it useful for the preparation of fluoro-compounds such as thyroid inhibitor.

Abstract: A 2-halopyridine-6-sulfonic acid and its salt represented by the formula: ##STR1## wherein X is a halogen atom, and M is a hydrogen atom or a metal atom. The compounds are useful as intermediates for producing fluorinating agents (reagents for introducing fluorine atoms).

Abstract: Fluoroalkylaryliodonium compounds having the formula (I): ##STR1## wherein AR, A and Rf are as defined above, are disclosed. The fluoroalkylaryliodonium compounds of the present invention are useful as intermediates for producing N-fluoroalkylanilines or derivatives thereof which are important precursors for fluorine-containing disperse azo dyes having an excellent resistance to light.

Abstract: A process for producing 5-fluorouracil using an aqueous phosphoric acid solution as a solvent which is a good solvent for an intermediate resulting from the reaction between uracil and elemental fluorine, and permits the reaction to proceed smoothly, but which can precipitate the final product, 5-fluorouracil, after cooling the heat-treated reaction solution to room temperature, with no need to evaporate the solvent.The process comprises reacting uracil in an aqueous phosphoric acid solution with elemental fluorine and heating the resultant reaction solution to form 5-fluorouracil.

Abstract: Perfluoroalkyl compounds represented by the formula (I): ##STR1## wherein R.sub.f represents a perfluoroalkyl group having 1 to 20 carbon atoms, Ar represents a substituted or unsubstituted phenyl group wherein the substituent is an alkyl group having 1 to 4 carbon atoms or a halogen atom, I represents an iodine atom, and A represents a perfluoroalkyl group having 1 to 20 carbon atoms which can be the same or different from R.sub.f, a hydroxy group an alkyl group having 1 to 4 carbon atoms, an aryl group or a halogen atom, and processes for preparing the perfluoroalkyl compounds represented by the formula (I).

Abstract: Perfluoroalkyl compounds represented by the formula (I): ##STR1## wherein R.sub.f represents a perfluoroalkyl group having 1 to 20 carbon atoms, Ar represents a substituted or unsubstituted phenyl group wherein the substituent is an alkyl group having 1 to 4 carbon atoms or a halogen atom, I represents an iodine atom, and A represents a perfluoroalkyl group having 1 to 20 carbon atoms which can be the same or different from R.sub.f, a hydroxy group an alkyl group having 1 to 4 carbon atoms, an aryl group or a halogen atom, and processes for preparing the perfluoroalkyl compounds represented by the formula (I).

Abstract: 4-Oxy-6-alkenyl-bicyclo[3.1.0]hexan-2-one compounds represented by the formula (I) ##STR1## wherein R represents a hydrogen atom or a protective group for a hydroxy group, R.sup.1 represents an alkyl group having 1 to 4 carbon atoms or an aryl group, R.sup.2 represents a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms and R.sup.3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms;4-oxycyclopentanone compounds represented by the formula (II) ##STR2## wherein R, R.sup.2 and R.sup.3 are as defined above, R.sup.4 represents a hydroxymethyl group, a methylene group (.dbd.CH.sub.2) or a --COOR.sup.1 group wherein R.sup.1 is as defined above, and R.sup.5 represents an alkyl group having 1 to 4 carbon atoms or an aryl group, useful as prostaglandin precursors; and processes for preparing the same.

Abstract: 2-Nitroethylcyclopentane compounds represented by the formula (I) ##STR1## wherein X represents a ##STR2## R and R.sup.1 each represents a hydrogen atom or a protective group for a hydroxy group, R.sup.2 represents an unsubstituted or substituted alkyl group having 1 to 8 carbon atoms and R.sup.5 represents a hydrogen atom or an alkyl group havng 1 to 4 carbon atoms, which are useful as intermediates for the synthesis of prostaglandin compounds, and a process for preparing the 2-nitroethylcyclopentane compounds of the formula (I).