NISCAIR Online Periodicals Repository Collection: IJC-B Vol.45B(01) [January 2006]

Novel approach for the rapid and efficient synthesis of heterocyclic Schiff bases and azetidinones under microwave irradiation

Title: Novel approach for the rapid and efficient synthesis of heterocyclic Schiff bases and azetidinones under microwave irradiation

Authors: Naik, Bhanvesh; Desai, K R

Abstract: A series of compounds, viz. 3′′-chloro-4′′-(substituted phenyl)-1′′-[4-(coumarin-3-yl)thiazol-2-yl]-2′′-azetidinones 4a-j have been prepared by the reaction of 2-N-(substituted benzylidene)imino-4-(coumarin-3-yl)thiazoles 3a-j with chloroacetyl chloride in the presence of triethylamine. The Schiff bases 3a-j have been prepared by the condensation of 2-amino-4-(coumarin-3-yl)thiazole 1 with different aldehydes 2. Both the reactions are carried out by conventional and microwave methods. The products are screened for their antibacterial activity against Staphylococcus aureus, Bacillus subtillis, Escherichia coli and Salmonella typhi

Page(s): 267-271

Chemoselective Knoevenagel reaction as a novel route for the synthesis of biscoumarinyl methylsulphones and 4+1, 1+4 approach synthesis of aminooxadiazolyl and N-(2,5-dimethyl)pyrrolylcoumarins

Title: Chemoselective Knoevenagel reaction as a novel route for the synthesis of biscoumarinyl methylsulphones and 4+1, 1+4 approach synthesis of aminooxadiazolyl and N-(2,5-dimethyl)pyrrolylcoumarins

Authors: Alawandi, Ganesh N; Kulkarni, Manohar V

Abstract: 4-Bromomethylcoumarins 1 on reaction with thiourea gives 4-mercaptomethyl coumarins 2, which on further reaction with ethyl chloroacetate afford the corresponding sulphide esters 3a-c. The sulphone esters 3d-f which are obtained upon oxidation of compounds 3a-c, undergo cyclisation with salals through Knoevenagel reaction to furnish biscoumarins 4 in good yield. Also esters 3a-f on reaction with hydrazine hydrate (99.9%) give the corresponding carbohydrazides 5. Compounds 5 when reacted separately with cyanogen bromide and acetonyl acetone yield aminooxadiazolyl 6 and N-(2,5-dimethyl)pyrrolylcoumarins 7, respectively. The compounds have been characterized by elemental analysis, IR, ¹H NMR, mass and 2D-HOMO COSY data. All the newly synthesized compounds have been screened for antimicrobial activity against gram-ve bacterium Escherishia coli, gram+ve bacterium Bacillus staphylococci and fungi penicillium and Aspergillus.

Page(s): 258-266

Antioxidant and antimicrobial activity evaluation of polyhydroxycinnamic acid ester derivatives

Title: Antioxidant and antimicrobial activity evaluation of polyhydroxycinnamic acid ester derivatives

Authors: Venkateswarlu, Somepalli; Ramachandra, Marellapudi S; Krishnaraju, Alluri V; Trimurtulu, Golakoti; Subbaraju, Gottumukkala V

Abstract: Polyhydroxycinnamic acid esters 5a-p have been synthesized starting from the appropriately substituted benzaldehydes. The antioxidant activity of these esters has been determined by superoxide free radical scavenging activity and DPPH free radical scavenging activity. The SAR studies reveal that pyrogallol, catechol moieties are essential for good antioxidant activity and an increase in the length of alkyl chain of the ester decreases the activity. Butyl hydroxycinnamates exhibit higher antibacterial activity among the synthesized hydroxycinnamates 5a-p, but, none of these show significant antifungal activity.

Page(s): 252-257

A simple synthesis of 5-spirobarbituric acids and transformations of spirocyclopropanobarbiturates to 5-substituted barbiturates

Title: A simple synthesis of 5-spirobarbituric acids and transformations of spirocyclopropanobarbiturates to 5-substituted barbiturates

Authors: Singh, Palwinder; Paul, Kamaldeep

Abstract: The reactions of barbituric acid and its 1,3-dimethyl derivative with 1,2-dibromoethane, 1,4-dibromobutane, 1,5-dibromopentane and 1,2-bis[bromomethyl] benzene in DMF-K₂CO₃ (base), TBAHSO₄ (catalyst) provide 5-spirobarbiturates as major products along with other products. The 5,7-dimethyl-5,7-diaza-spiro[2.5]octane-4,6,8-trione undergoes ring opening with ^-CN, ^-SR and Br₂ to provide 5-substituted barbiturates.

Page(s): 247-251