the solvent used provided it does not inhibit the reaction and dissolves the starting material to a certain degree preferred examples include aromatic hydrocarbons such as benzene toluene and xylene halogenated hydrocarbons such as dichloromethane and chloroform esters such as ethyl acetate and propyl acetate ethers such as diethyl ether tetrahydrofuran 1 4 dioxane and 1 2 dimethoxyethane alcohols such as methanol and ethanol nitriles such as acetonitrile amides such as formamide and n n dimethylformamide sulfoxides such as dimethyl sulfoxide a mixture of multiple organic solvents in an arbitrary ratio and in addition a mixture thereof with water in an arbitrary ratio although there are no particular limitations on the acid used provided it is used as an acid in conventional reactions examples include inorganic acids such as hydrochloric acid and sulfuric acid lewis acids such as boron trifluoride boron trichloride boron tribromide and iodotrimethylsilane and organic acids such as trifluoroacetic acid varying according to the raw material compounds reagents and the like the reaction temperature is normally u2212 100 u00b0 c to 150 u00b0 c preferably u2212 78 u00b0 c to 100 u00b0 c varying according to the raw material compounds reagents and the like the reaction time is normally 5 minutes to 24 hours preferably 10 minutes to 12 hours following completion of the reaction the desired compound can be obtained as a solid by distilling off the organic solvent adding water and then adding a base on the other hand in the case where a solid is unable to be obtained by adding a base the desired compound can be obtained.