A green, straightforward, and efficient protocol for the synthesis of a new series of isoxazolyl chromeno[2, 3-b]pyridine-3carboxylate derivatives have been reported by one-pot reaction of isoxazolyl enamino esters and 3-formylchromones by employing water as a reaction medium and polyethylene glycol-400 (PEG-400) as the green promoter. The superiority of this protocol is environmentally benign, simple operation, metal-free, broad substrate scope, good yields, less reaction time and PEG-400 can be recovered and reused. Most significant of all, this protocol is green.

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A series of novel isoxazolyl-1,4-benzodiazepine-5-ones 4 have been synthesized by the reaction of phenacyl isoxazolylamines 1 with o-nitrobenzoic acids 2 to furnish different (E)-N-(3methyl-5-styrylisoxazol-4-yl)-2-nitro-N-(2-oxo-2-phenylethyl) benzamides 3, which on treatment with Fe-AcOH underwent reductive cyclization to afford the target compounds 4 a-w. The newly synthesized compounds were characterized by IR, 1 H NMR, 13 C NMR, and HRMS analysis. The target compounds 4 a-w were evaluated for their in vitro antimicrobial activity. Among the synthesized compounds, compounds 4 r, 4 s, 4 t, 4 u, 4 v and 4 w showed potent antimicrobial activity as compared with the reference drugs. Most of the newly synthesized title compounds have shown good to excellent antimicrobial activity. Results and DiscussionThe key building blocks for the synthesis of the title compounds 4 a-w were phenacyl isoxazolylamines [15f] and o-nitrobenzoic acids. A general synthetic protocol of isoxazolyl-1,4-benzodiaze-[a] R.

Impurities of oseltamivir phosphate were synthesized from chiral epoxide (1) in a simpler and much feasible synthetic approach in seven steps accounting to 8.2 % overall yield. The nucleophilic addition of N3 (highly regioselective and stereoselective) in the first and third stage of the synthesis has been tailored and the reaction conditions were optimized.