Abstract

A convenient synthetic approach leading to synthesize a series of novel substituted azoles, azines and azepines linked to α-aminophosphonate moiety was achieved. The methodology depends on ring-opening and ring-closure (RORC) of chromone ring of diethyl chromonyl α-aminophosphonate 1 via its reaction with nitrogen nucleophiles such as primary amines, 1,2-, 1,3- and 1,4-bi-nucleophiles in ethanolic sodium ethoxide. Also, treatment of compound 1 with some acyclic and cyclic active methylene compounds under the same reaction conditions afforded interesting novel isolated and fused pyridine systems bearing phosphonate groups at α-position. The screening of antimicrobial activity for the synthesized compounds indicates that connection of pyrazole, oxazepine and benzodiazepine rings with α-aminophosphonate moiety exhibited good antimicrobial effects. Also, evaluation of their antioxidant properties exemplifies that the compounds having 1,5-benzoxazepinyl and 1,5-benzodiazepinyl units in combination with α-aminophosphonic diester moiety are the most powerful antioxidant agents.

Highlights

  • INTRODUCTIONChromone compounds have attracted considerable attention as highly reactive compounds, which can serve as starting materials in synthesis of a whole series of heterocycles with useful properties due to two strong electrophilic centers (carbon atoms C−2 and C−4 of the chromone system).[1,2] The 3-heteroaryl chromones possess

  • There is a need to search for new methods, which could be more useful in preparation of α-heterocyclic α-aminophosphonates

  • Compared to the previously reported methodologies, the present article offers procedure for synthesis of parent heterocyclic α-aminophosphonate and phosphonates which are an inapplicability of known via the regular procedures

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Summary

INTRODUCTION

Chromone compounds have attracted considerable attention as highly reactive compounds, which can serve as starting materials in synthesis of a whole series of heterocycles with useful properties due to two strong electrophilic centers (carbon atoms C−2 and C−4 of the chromone system).[1,2] The 3-heteroaryl chromones possess. The 17th International Electronic Conference on Synthetic Organic Chemistry in 1-30 November 2013 a highly polarized C2−C3 π-bond and their reactions with bi-nucleophiles occur predominantly via a nucleophilic attack on the unsubstituted C−2 atom (1,4-addition) and are accompanied by ring-opening to form the β-carbonyl intermediate capable of undergoing intramolecular heterocyclization.[3,4] On the other hand, α-aminophosphonates act as important family of organophosphorus compounds which possesses various important biological properties.[5,6] Some of these biological activities are enzyme inhibition,[7] antitumor,[8] antibiotics[9] and antiproliferative.[10] α-Aminophosphonates containing five- and six-membered heterocycles at α-position are known.[11,12,13,14,15,16] To the best our knowledge, α-aminophosphonates possess sevenmembered heterocycles at α-position have not been reported hitherto. In continuation of our interest in the synthesis of new α-aminophosphonates containing different bioactive heterocyclic rings,[17−19] we report an efficient synthesis of novel α-aminophosphonates containing different nitrogen heterocycles and α-pyridinyl phosphonates were achieved. The antimicrobial activities and antioxidant properties of the synthesized compounds were evaluated

RESULTS AND DISCUSSION
H OEt PO
H PO OEt
CONCLUSION
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