Patent GB-638895-A (GB)
Title: Improvements in or relating to cyclic acetals
Filed: 1947-12-23
Abstract: Cyclic aminobenzaldehyde acetals of 1 : 2-and 1 : 3-glycols, the glycol residues containing 2-4 carbon atoms, are distilled, preferably under reduced pressure (e.g. below 10 mm.), in the presence of at least 0.0025 (preferably at least 0.005, if desired up to 0.025) mol. equivalents of non-volatile alkali, e.g. the hydroxides, carbonates, oxides, amides or alkoxides of lithium, sodium or potassium, the oxides or hydroxides of calcium or barium, or non-volatile amides or nitrogen compounds of the tertiary (R3N) or quaternary (R4NOH) classes (R being an alkyl group, such as dodecyl or hexadecyl, or an aralkyl group, such as benzyl), especially those having vapour pressures of 1 mm. or lower at 150 DEG  C. or above (e.g. dimethyloctadecylamine or tetramethylammonium hydroxide).ALSO:Polyvinyl acetals, containing the residues of colour-formers (e.g. b -ketoacylamides, pyrazolones, benzyl cyanides, indoxyls, thioindoxyls, homophthalimides, 2 : 4 - dihydroxyquinoline, diketohydrindene, malonamides, phenacylpyridinium halides or hydroxypyridine), are manufactured by acetal interchange between polyvinyl alcohol and a compound formed by the acylation, with carboxylic or sulphonic acid or acid chloride derivatives of colour-formers, of the cyclic acetals of aminobenzaldehydes (which may be further substituted in the nucleus by hydrocarbon or hydrocarbon ether radicals) with 1 : 2- or 1 : 3-glycols, the glycol residues containing 2-4 carbon atoms.ALSO:Cyclic aminobenzaldehyde acetals of 1 : 2-and 1 : 3-glycols, the glycol residues containing 2-4 carbon atoms, are manufactured by reducing the corresponding cyclic acetals of nitrobenzaldehydes (which may be further substituted in the benzene nucleus by monovalent hydrocarbon or hydrocarbon ether radicals, preferably lower alkyl or alkoxy radicals).  The reduction may be carried out by chemical means (e.g. with sodium or ammonium sulphides or by sodium in alcohol), but is preferably effected by the action of hydrogen, preferably at elevated temperatures and pressures (e.g. 50-100 DEG  C. and 100-2000 lbs. per sq. inch), in the presence of a hydrogenation catalyst (e.g. nickel, ruthenium, palladium, platinum, cobalt, copper chromite or cobalt sulphide, if desired supported on inert carriers, such as kieselguhr), and, if desired, in the presence of a solvent (e.g. methanol, ethanol, propanol, benzene, toluene or hexane).  The products may be recovered from the reaction mixture by distillation, preferably under reduced pressure, in the presence of at least 0.0025 (preferably at least 0.005, if desired up to 0.025) mol. equivalents of non-volatile alkali.  Suitable alkalies (which may also be used for stabilizing the products to heating in other circumstances) are the hydroxides, carbonates, oxides, amides and alkoxides of lithium, sodium and potassium, the oxides and hydroxides of calcium and barium, also non-volatile amides and nitrogen compounds of the tertiary (R3N) or quaternary (R4NOH) classes (R being an alkyl group, such as dodecyl or hexadecyl, or an aralkyl group, such as benzyl), especially those having vapour pressures of 1 mm. or lower at 150 DEG C. or above (e.g. dimethyloctadecylamine or tetramethylammonium hydroxide). The starting materials are obtainable by reacting a nitrobenzaldehyde with the cyclic sulphite of ethylene glycol, or by preparing the dimethyl acetal from a nitrobenzaldehyde and methanol or dimethyl sulphite and heating with a glycol in the presence of an acid catalyst, or especially by reacting a nitrobenzaldehyde with a 1 : 2- or 1 : 3-glycol containing 2-4 carbon atoms, under acetalforming conditions (e.g. by heating in the presence of an acid catalyst, such as phosphoric, sulphuric, hydrochloric or p-toluenesulphonic acid, and a water-entraining solvent, such as benzene, toluene, xylene or chlorobenzene). Examples describe the preparation and reduction of the ethylene glycol acetals of m- and p-nitrobenzaldehyde, 3 - nitro - 4 - methoxybenzaldehyde and 3-nitro-p-tolualdehyde, and the trimethylene glycol acetal of m-nitrobenzaldehyde.  Other glycols specified are 1 : 2-propylene glycol and 1 : 2- and 1 : 3-butylene glycols.  The products may be acylated with carboxylic or sulphonic acids or acid chlorides containing the radicals of colour formers, such as b -ketoacylamides, benzyl cyanides, indoxyls, thioindoxyls, homophthalimides, pyrazolones, 2 : 4 - dihydroxyquinoline, diketohydrindene, malonamides, phenacylpyridinium halides or hydroxypyridine, e.g. with p-acetoacetaminobenzoic acid, 1 - p - carboxyphenyl - 3 - methyl - 5-pyrazolone and 1 - phenyl - 3 - carboxy - 5 - pyrazolone.ALSO:Azo dyes are obtainable from cyclic acetals of aminobenzaldehydes (which may be further substituted in the nucleus by hydrocarbon or hydrocarbon ether radicals) with 1 : 2- or 1 : 3-glycols (the glycol residue containing 2-4 carbon atoms), by diazotization and coupling with an azo dye coupling component or with a preformed azo dye, or by joining a dye to the acetal through an amide or sulphonamide group.