Process for the preparation of cephalosporins

Details Process for the preparation of cephalosporins Process for the preparation of cephalosporins

C - Chemistry, Metallurgy

07

D

260/103

C07D 501/08 (2006.01) C07D 205/095 (2006.01)

Patent

CA 1060433

ABSTRACT OF THE DISCLOSURE A process is disclosed for preparing cephalosporins of the structure: Image I wherein R is selected from the class consisting of hydrogen, alkyl having from 1 to 4 carbon atoms, t-butoxy,benzyloxy, cyano-methyl, thienyl-methyl, furyl-methyl, naphthyl-methyl, phenyl-methyl, phenoxy-methyl, phenoxy-isopropyl, pyridyl-4- thiomethyl and tetrazolyl-1-methyl; R1 is selected from the class consisting of hydroxyl, alkoxy with 1 to 4 carbon atoms, benzyloxy, p-methoxy-benzyloxy, p-nitro-benzyloxy, benzhydryloxy, triphenylmethoxy, phenacyloxy, p-halophenacyloxy and tri- chloroethoxy; Z is selected from the class consisting of hydrogen, hydroxyl, -O-CO-alkyl, -O-alkyl, -Br, -I, -Cl, -N3, -NH2, -O-CO-CH3, -O-CO-NH2 and an -S-mononuclear nitrogen heterocyclic ring, the alkyls having from 1 to 4 carbon atoms; wherein compounds of structure: Image Image II (E isomer) III (Z isomer) n which R, R1, and Z are as above defined; R2 and R3 are equal or different and represent a lower alkyl group having from 1 to 4 carbon atoms, a mononuclear aryl ring, -CN, a mononuclear Abstract continued..... heterocyclic ring or the radicals -COR4, COOR4, -PO(OR4)2, -CO-NHR4 or R2 and R3 together may represent the residues: Image Image where T represents ?CH2, -N-R4; and R4 is a lower alkyl, a mononuclear aryl ring or a mononuclear heterocyclic ring, are reacted singly or as mixtures with each other in a suitable solvent at a temperature between -100° and +120°C with a strong base to finally give a compound of formula I that is a mixture of .DELTA.2 and .DELTA.3 cephem-derivatives from which the .DELTA.3 cephem derivatives can be obtained. The strong base used for converting the intermediates of formula II or III to the desired compound I is selected from the class consisting of alkali metal alcoholates and thioalcoholates; alkali metal phenates and thiophenates having one or more substituents in the aromatic ring; an alkali metal amide such as the lithium, sodium or potassium amide of the di-isopropylamides, dicyclohexyl- amides, isopropyl-cyclohexylamides; an organometallic compound such as phenyl-lithium, a C1-4 alkyl-lithium, lithium, sodium or potassium triphenylmethane; a lithium hexamethyl- disilazane, an alkali metal hydride or a conjugate base of a dialkyl sulphoxide. The solvent used for converting the intermediates of formula II or III to the desired compound I is tetrahydrofuran, diethyl ether, dimethylformamide, dimethylsulphoxide, diglyme or hexamethylphosphorustriamide.

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