- Propenyl cephalosporin derivatives and process for the manufacture thereof
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Disclosed are cephalosporin derivatives of the general formula wherein R is an organic residue with a molecular weight not exceeding 400 bonded to the adjacent sulphur atom via carbon and consisting of carbon, hydrogen, and optional oxygen, sulfur, nitrogen and/or halogen atoms; R1 is hydrogen, lower alkyl or phenyl; and A is a secondary, tertiary or quaternary nitrogen atom bound directly to the propenyl group and being substituted by an organic residue with a molecular weight not exceeding 400 and consisting of carbon, hydrogen, and optional oxygen, sulfur, nitrogen and/or halogen atoms,as well as readily hydrolyzable esters thereof, pharmaceutically acceptable salts of said compounds and hydrates of the compounds of formula I and of their esters and salts.
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- Metallation reactions XXII. Regioselective metallation of (trifluoromethyl) (alkylthio) benzenes
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The metallation reactions of (trifluoromethyl)(alkylthio)benzenes with organolithium reagents and with the butyllithium/potassium tert-butoxide superbasic mixture are here described. The results, according to the theoretical calculations of energy minima, show the monometallation regiochemistry is directed by the sulphur atom. On the other side, the bimetallation, that can be performed only on methylthio derivatives, depends on the organometallic reagent employed. Using butyllithium the stronger coordinative power of sulphur prevails and products metallated in ortho and alpha positions to this atom are mainly formed. With the more basic sec-butyllithium and with the Superbase, because of mutual competition between the thioalkyl and trifluoromethyl groups, mixtures of products, coming from metallation in the ortho position to the trifluoromethyl group and in the alpha position of the thiomethylic group, are obtained. In addition, products coming from substitution ortho,alpha to the thiomethyl group are also formed. All mono- and bimetallated intermediates showed to be good synthons for the synthesis of fluoro- and (trifluoromethyl)-substituted benzothiophenes and (trifluoromethyl)benzenes substituted on the thioalkylic chain and/or on the ring.
- Cabiddu,Cabiddu,Cadoni,Corrias,Fattuoni,Floris,Melis
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p. 125 - 140
(2007/10/03)
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