Process for preparing desacetoxycephalosporins

A process for preparing a desacetoxycephalosporin from a penicillin sulfoxide of the formula ##SPC7##

• in which R.sub.3 is hydrogen and R.sub.4 is hydrogen;
• C.sub.1 -C.sub.8 alkanoyl;
• azidoacetyl;
• cyanoacetyl;
• haloacetyl;
• ##EQU16## in which Ar is phenyl, thienyl, furyl, pyrrolyl, or phenyl substituted with from one to three substituents selected from the group consisting of fluorine, chlorine, bromine, iodine, trifluoromethyl, C.sub.1 -C.sub.3 acyloxy, hydroxy, C.sub.1 -C.sub.3 alkyl, C.sub.1 -C.sub.3 alkoxy, cyano, and nitro;
• ##EQU17## in which Ar' is phenyl, pyridyl, or substituted phenyl as defined above, and Y is oxygen or sulfur;
• ##EQU18## in which Ar is as defined above, and B is C.sub.1 -C.sub.3 acyloxy, hydroxyl, carboxyl, esterified carboxyl, --CN, --N.sub.3, --NH.sub.2, or --NHR in which R is benzyloxycarbonyl, C.sub.1 -C.sub.4 alkoxycarbonyl, cycloalkoxycarbonyl, triphenylmethyl, ##EQU19## or 2,2,2-trichloroethoxycarbonyl;
• (3-sydnone)-C.sub.2 -C.sub.3 alkanoyl;
• ##SPC8##
• in which R' is hydrogen or methoxy;
• 2-(1H-tetrazol-1-yl)acetyl;
• or R.sub.3 and R.sub.4 taken together with the nitrogen atom to which they are bonded are phthalimido, a cyclic imide moiety of a C.sub.3 -C.sub.12 dicarboxylic acid, 2,2-dimethyl-5-oxo-4-phenylimidazolidin-1-yl, or 2,2-dimethyl-3-nitroso-5-oxo-4-phenylimidazolidin-1-yl;
• and R.sub.2 is hydrogen, C.sub.1 -C.sub.6 alkyl, 2,2,2-trihaloethyl, 2-iodoethyl, benzyl, nitrobenzyl, tetrahydropyranyl, 9-fluorenyl, succinimidomethyl, phthalimidomethyl, methoxybenzyl, dimethoxybenzyl, cyanomethyl, nitrophenyl, dinitrophenyl, 2,4,6-trinitrophenyl, bis(p-methoxyphenyl)methyl, triphenylmethyl, benzhydryl, benzyloxymethyl, C.sub.2 -C.sub.6 alkanoyloxymethyl, C.sub.2 -C.sub.4 alkanoyl, phenacyl, or a radical of the formula ##EQU20## in which each R.sub.1 independently is c.sub.1 -C.sub.4 alkyl or phenyl;
• which comprises heating the penicillin sulfoxide in an inert, substantially anhydrous solvent to a temperature of from about 75.degree.C. to about 150.degree.C. in the presence of from about 1.1 to about 4 equivalents of a silylating agent of the formula
• a. ##EQU21## in which each R.sub.1 independently is C.sub.1 -C.sub.4 alkyl, or phenyl, R'" is hydrogen, C.sub.1 -C.sub.4 alkyl, or phenyl, and X is ##EQU22## in which J is hydrogen or --Si(R.sub.1).sub.3, or X is --CW.sub.3 in which each W independently is hydrogen, trifluoromethyl or C.sub.1 -C.sub.3 alkyl;
• b. ##EQU23## in which R.sub.1 and W are as herein defined;
• and c. Z--Si(R.sub.1).sub.3
• in which R.sub.1 is as herein defined and Z is halogen, C.sub.2 -C.sub.3 alkenyloxy, C.sub.1 -C.sub.3 alkyl--SO.sub.3 --, --O--Si(R.sub.1).sub.3, --S--Si(R.sub.1).sub.3, or ##EQU24## in which R.sub.5 is hydrogen or c.sub.1 -C.sub.3 alkyl, and R.sub.6 is C.sub.1 -C.sub.4 alkyl or --Si(R.sub.1).sub.3, or R.sub.5 and R.sub.6 taken together with the nitrogen atom to which they are bonded form a heterocyclic ring having 5 or 6 atoms, up to 3 of which, in addition to the already-defined nitrogen atom, independently are nitrogen, sulfur, or oxygen;
• and simultaneously or subsequently treating the reaction mixture in an acidic medium selected from the group consisting of a mineral acid, a sulfonic acid, and a Lewis acid.