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Synthesis of heterocyclic methylenebisphosphonates by 1,3-dipolar cycloaddition of ethyl diazoacetate to 1,2-benzoxaphosphorin-3-phosphonates |
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| Authors: | Nevena I Petkova Anka G Bojilova Jurgen Kopf |
| Institution: | a Department of Organic Chemistry, University of Sofia, 1, J. Bourchier Ave., Sofia 1164, Bulgaria b Department of Chemistry, Aristotle University of Thessaloniki, GR-54006 Thessaloniki, Greece c Institute of Inorganic and Applied Chemistry, University of Hamburg, Martin-Luther-King Pl. 6, D-20146 Hamburg, Germany |
| Abstract: | Reaction of salicylaldehydes with tetraethyl ester of methylenebisphosphonic acid, under Knoevenagel reaction conditions, gives the corresponding 1,2-benzoxaphosphorin-3-phosphonates 5 in good yields. The 3+2] regio- and stereoselective cycloaddition of 5a and 5b with ethyl diazoacetate gives two P-4 epimers of the corresponding pyrazoline bisphosphonate tetraethyl esters 9 and 10. Analogously, ethyl diazoacetate reacts with 1 and 2 to give the expected pyrazolines 6-8. The structures of the new compounds are revealed and confirmed by analytical, spectroscopic data and X-ray crystallographic analysis. |
| Keywords: | Knoevenagel reaction 1 2-Benzoxaphosphorines [3+2]Cycloaddition Pyrazoline bisphosphonate esters Coumarins |
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