Monoacetals or aromatic 1,2-diketones

Claim 1

Process for the production of monoacetals of aromatic diketones of formula I ##STR10## wherein R 1 represents hydrogen, alkyl having 1 to 5 carbon atoms, alkenyl having 2 or 3 carbon atoms, aralkyl having 7 to 9 carbon atoms, aralkenyl having 8 or 9 carbon atoms, or a group --(CH 2 ) n --X, wherein n represents a whole number from 1 to 3, and X denotes halogen, --OR 3 , --SR 3 , --OAr 3 , --SAr 3 ##STR11## and R 3 represents alkyl having 1 to 4 carbon atoms, Ar 1 , Ar 2 and Ar 3 each independently represent a phenyl radical unsubstituted, or at most trisubstituted by halogen, alkyl or alkoxy having 1 to 4 carbon atoms or by phenyl, which process comprises reacting an aromatic 1,2-diketone of the formula Ar 1 --CO--CO--Ar 2 either with a sulphurous acid ester of the formula (R 1 CH 2 O) 2 SO in the presence of an anhydrous acid and a primary monoalcohol R 1 CH 2 OH at a temperature of about 20° to 120° C. or with thionyl chloride and a primary monoalcohol R 1 CH 2 OH at a temperature of from about 0° to 20° C. and subsequently heating to from about 20° to 120° C.