Abstract: A process for preparing acid chlorides, wherein a silyl ester having an aliphatic, aromatic, alkanoaromatic or heterocyclic group which may support substituents, and having a low molecular weight alkyl or phenyl group is reacted with thionyl chloride in an inert solvent at a temperature of from -15.degree. to 50.degree. C, preferably from 10.degree. to 50.degree. C.

Abstract: A process consisting in reacting one mole of an alpha-halobenzyl penicillin-(s)-sulphoxide with at least two moles of 3-trimethylsilyl-2-oxazolidinone (TMSO) at a temperature of between 60 and 120.degree. C in acetonitrile solution in the presence of a tertiary organic base p-toluene sulphonate and thiourea is described. The solvent is removed by evaporation from the solution obtained, the residue is diluted with water, the pH is adjusted to 4.2 and 7-aminodesacetoxycephalosporanic acid (7-ADCA) is isolated.

Abstract: The process consists in reacting 2-oxazolidinone or 5-methyl-2-oxazolidinone, with trimethylchlorosilane or dimethylchlorosilane, or triethylchlorosilane, in the presence of an organic tertiary base acting as a hydrogen chloride removal agent, the resulting compound is reacted with 6-APA, 7-ACA or 7-ADCA; the resulting compound is reacted with an activated carboxylic acid to obtain an N-acyl derivative, which, when treated with water or alcohols gives a penicillin or cephalosporin.

Abstract: Silylating agents, such as 3-alkylsilyl-2-oxazolidinones, are useful for the preparation of penicillins and cephalosporins at low temperatures and in a short time. The process for preparing these compounds comprises reacting 2-oxazolidinone or 5-methyl-2-oxazolidinone with trimethylchlorosilane, dimethylchlorosilane or triethylchlorosilane, in the presence of an organic tertiary base acting as a hydrogen chloride removal agent.