104599-90-8

The Rh(III)-catalyzed selective bromination and iodination of electron-rich heterocycles is reported. Kinetic investigations show that Rh plays a dual role in the bromination, catalyzing the directed halogenation and preventing the inherent halogenation of these substrates. As a result, this method gives highly selective access to valuable halogenated heterocycles with regiochemistry complementary to those obtained using uncatalyzed approaches, which rely on the inherent reactivity of these classes of substrates. Furans, thiophenes, benzothiophenes, pyrazoles, quinolones, and chromones can be applied.

A series of 1 -cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-[chloro/1 -piperazinyl/4-methyl-1-piperazinyl/4-ethyl-1-piperazinyl/ 4-hydroxyethyl-1- piperazinyl/imidazolyl/morpholinyl]-3[N-(substituted phenyl amino) carbonyl]quinoline 5-11a-j have been prepared by using substituted arylamine at C-3 position and 1-piperazine/4-methyl-1-piperazine/4-ethyl-1-piperazine/4- hydroxyethyl-1-piperazine/imidazole/morpholine at C-7 position of newly synthesized quinolone 3. Biological profile like antibacterial activity against four different strain viz. S. aureus and B. subtilis (gram-positive bacteria) and E. coli and P. aeruginosa (gram-negative bacteria) and C. albicans (fungi) by cup plate method have been studied.

Two new derivatives from the ciprofloxacin fluoroquinoline family, 7-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo- quinoline-3-methylcarbamate and 1-cyclopropyl-7-(4-ethyl-1-piperazinyl)-6-fluoro-1,4-dihydro-(3-oxopyrazolo) [4,3-c]quinoline, were synthesised, tested for antibacterial activity and crystallised. Their molecular and crystal structures were determined. Tests in vitro reveal lower activities than for ciprofloxacin. Characteristic structural features of these compounds are comparable to data for other known fluoroquinolines. The bicyclic quinoline ring is planar in both compounds; the carbamate side chain and five-membered pyrazolo ring are almost coplanar with it. A piperazinyl ring exhibits a chair conformation. In the crystal packing of the carbamate analogue, two C-HO interactions form a dimer. The pyrazolo derivative crystallises as solvate with 1.5 water molecules per quinoline molecule. In its crystal structure donor and acceptor functionalities form dimers, via hydrogen bonds, which are connected into an infinite pattern through hydrogen bonded water molecules.

Electrochemical studies of 1-cyclopropyl-6-fluoro-1,4-dihydro-7-(N- piperazinyl)-4-oxo-3-quinoline carboxylic acid 5 and its synthetic precursors, viz., 2, 4-dichloro-5-fluoroacetophenone 1, 3-cyclopropylamino-2- (2,4-dichloro-5-fluorobenzoyl)acrylic acid methyl ester 2, 7-chloro-1- cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid methyl ester 3 and 7-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-quinoline-3- carboxylic acid 4 are reported. Plausible electrochemical mechanism for the reduction of the series of compounds is suggested based on cyclic voltammetry, coulometry and spectral studies. The role of resonance isomerism aided by intramolecular hydrogen bonding and aromaticity, in the electrochemistry of compounds 2-5, is discussed. The acid-base equilibria of the compounds are revisited based on PCMODEL MMX Molecular Energy Minimisation Software and cyclic voltammetry. An excellent electroanalytical method in differential pulse polarography for the quantitative analysis of the drug 5 and its synthetic precursors 14 is developed.

Starting with o-halobenzoyl chlorides 4 and open-chain secondary enamines 5, a new synthesis of 4-quinolone-3-carboxylic acids 12 is described.The reaction of 7-haloquinolone-3-carboxylic acids 12a-k with aliphatic amines 14 produces highly active antibacterial 7-aminoquinolone-3-carboxylic acids 15.The main product of the 1-cyclopropyl series, "ciprofloxacin" (15a), is being developed as a broad-spectrum chemotherapeutic agent.