Electrolytic reduction of cephalosporin p-nitrobenzyl esters

A process for preparing a compound of the formula ##STR5## wherein X is hydrogen;

• m is 0 or 1;
• R.sup.2 is hydrogen or methoxy;
• R is hydrogen or --COR.sup.3 ;
• R.sup.3 is hydrogen, C.sub.1 --C.sub.3 alkyl, halomethyl, benzyloxy, 2,2,2-trichloroethoxy, t-butoxy, R.sup.4, R.sup.4 --(O).sub.n --CH.sub.2 --, R.sup.4 --CH(R.sup.5)--, R.sup.6 --CH.sub.2 --, or ##STR6## wherein R.sup.7 is hydrogen or C.sub.1 -C.sub.3 alkyl and R.sup.8 is hydrogen or an amino-protecting group;
• R.sup.4 is cyclohexadienyl or phenyl, or cyclohexadienyl or phenyl substituted with one or two halo, hydroxy, protected hydroxy, aminomethyl, protected aminomethyl, C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy groups;
• n is 0 or 1;
• R.sup.5 is hydroxy, protected hydroxy, amino, protected amino, carboxy or protected carboxy;
• R.sup.6 is 2-thienyl, 2-furyl, 5-tetrazolyl or 1-tetrazolyl;
• R.sup.1 is C.sub.1 -C.sub.4 alkanoyloxy, benzoyloxy, fluoro, chloro, carbamoyloxy, C.sub.1 -C.sub.4 alkylcarbamoyloxy, pyridinio, pyridinio substituted with C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkanoyl, carbamoyl, C.sub.1 -C.sub.4 alkylcarbamoyl, chloro, fluoro, hydroxy or trifluoromethyl, or the corresponding pyridinio chlorides or bromides, or --S--R.sup.9 ;
• R.sup.9 is --CH.sub.2 CO.sub.2 (C.sub.1 -C.sub.4 alkyl), carbamoyl, phenyl, phenyl substituted with one or two chloro, fluoro, C.sub.1 -C.sub.4 alkyl, hydroxy, C.sub.1 -C.sub.4 alkylsulfonamido or trifluoromethyl groups;
• triazol-3-yl unsubstituted or substituted with one or two groups independently selected from C.sub.1 -C.sub.3 alkyl, --CO.sub.2 (C.sub.1 -C.sub.4 alkyl), --CONH.sub.2 and --CH.sub.2 NHOCO(benzyl or C.sub.1 -C.sub.4 alkyl);
• ##STR7## tetrazol-1-yl or tetrazol-5-yl substituted with one or two groups independently selected from C.sub.1 -C.sub.4 alkyl and --CH.sub.2 CO.sub.2 (C.sub.1 -C.sub.4 alkyl or hydrogen);
• 4-cyano-5-aminopyrimidin-2-yl, or 5-methyl-1,3,4-thiadiazol-2-yl;
• provided that n is 0 when R.sup.4 is cyclohexadienyl;
• which process comprises electrolytically reducing a compound of the above formula wherein X is p-nitrobenzyl in an acidic liquid medium comprising from about 0 to about 50% water, an acid having a pK.sub.a determined in water of 0 or below, the amount of said acid being at least four moles per mole of the compound to be reduced, and an organic solvent substantially inert to electrolytic reduction, at the working electrode of an electrolytic cell, said working electrode substantially comprising carbon, mercury, tin, aluminum, silver, copper, lead, chromium, zinc, nickel or cadmium, at a temperature from about 0.degree. C. to about 75.degree. C., at a potential in a range from about the potential of the initial onset of current flow of the first reduction to about the potential of the initial onset of current flow of the second reduction.