Process for preparing 3-hydroxy cephalosporins

A process for preparing a 3-hydroxycephalosporin of the formula ##STR19## which comprises reacting a compound of the formula ##STR20## with an amine selected from the group consisting of 1,5-diazabicyclo[5.4.0]undec-5-ene and 1,5-diazabicyclo[3.4.0]non-5-ene at a temperature of from about 0.degree. C. to about 25.degree. C., in which, in the above formulae, R.sub.1 is a carboxylic acid protecting group, and R is

• a. phthalimido,
• b. an amido group of the formula ##STR21##
• in which R.sub.2 is 1. hydrogen, C.sub.1 -C.sub.3 alkyl, halomethyl, thienyl-2-methyl, 4-protected-amino-4-protected carboxybutyl, benzyloxy, 4-nitrobenzyloxy, t-butyloxy, 2,2,2-trichloroethoxy, 4-methoxybenzyloxy;
• 2. a group of the formula R'--(O).sub.m --CH.sub.2 -- in which m is 0 or 1, and R' is phenyl or phenyl substituted with 1 or 2 halogens, protected hydroxy, nitro, cyano, trifluoromethyl, C.sub.1 -C.sub.4 alkyl, or C.sub.1 -C.sub.2 alkoxy;
• 3. a group of the formula ##STR22## in which R' is as defined above and W is protected hydroxy, protected carboxy, or protected amino;
• or
• c. an imidazolidinyl group of the formula ##STR23## in which R' is as defined above.