Process for preparing 2-chlorosulfinylazetidinones

In the process for preparing a 2-chlorosulfinylazetidin-4-one of the formula ##STR22## wherein R is hydrogen, C.sub.1 -C.sub.3 alkyl, halomethyl or cyanomethyl;

• or R is the group R' wherein R' is phenyl or phenyl substituted by 1 or 2 substituents selected from the group consisting of C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, halo, protected hydroxy, nitro, cyano and trifluoromethyl;
• or R is a group of the formula
• R"--O--
• wherein R" is t-butyl, 2,2,2-trichloroethyl, benzyl, 4-nitrobenzyl or 4-methoxybenzyl;
• or R is a group of the formula
• R'''(Z).sub.n CH.sub.2 --
• wherein R''' is R' as defined above, 2-thienyl, 3-thienyl, 2-furyl, 3-furyl or 1,4-cyclohexadienyl;
• n is 0 or 1, and Z is O or S, subject to the limitation that when n is 1, R''' is R';
• or R is a substituted aralkyl group of the formula ##STR23## wherein R''' has the same meanings as defined above and Q is protected hydroxy or protected amino;
• and R.sub.1 is a carboxylic acid protecting group, which comprises heating in an inert organic solvent a penicillin sulfoxide ester of the formula ##STR24## wherein R and R.sub.1 are as defined above, at a temperature between about 75.degree. C. and about 175.degree. C. with an N-chlorohalogenating agent, the improvement which consists of heating said penicillin sulfoxide ester with the N-chlorohalogenating agent in the presence of an organic solvent insoluble, weakly basic cross-linked poly-4-(vinylpyridine) polymer in a ratio by weight of said polymer to penicillin sulfoxide of between about 1:1 and about 1:5, wherein said polymer is cross-linked to between about 1 percent and about 10 percent with a cross-linking agent selected from among the group consisting of divinylbenzene, N,N'-methylenebisacrylamide, N,N'-decamethylenebisacrylamide, N,N-diallylacrylamide, ethylene diacrylate, ethylene dimethacrylate, 1,1,1-trimethylolpropane trimethacrylate, 1,1,1-trimethylolpropane triacrylate, 1,1,1-trimethylolethane triacrylate, 1,1,1-trimethylolethane trimethacrylate, pentaerythritol tetramethacrylate, 1,3,5-triacryloylhexahydro-s-triazine, 1,3,5-trimethacryloylhexahydro-s-triazine, diallyl phthalate, diallyl malonate, diallyl succinate, N,N-diallylpiperazine, tetraallyloxyethane, tetraallylpyromellitate, trivinylcyclohexane, and divinylsulfone.