Reactions of Azovinylphosphonates with Nucleophilic Alkenes and Heterocycles: Synthesis of Tetrahydropyridazine-3-phosphonate and 2-Substituted-1-hydrazonoethylphosphonate Derivatives

Abstract

Transient azovinylphosphonates, generated in situ by base induced dehydrohalogenation of the corresponding 2-bromo-and 2-chloro-acetylphosphonate-tertbutoxycarbonyl hydrazones are intercepted by electron rich alkenes and heterocycles in hetero Diels-Alder reactions, producing tetrahydopyridazine-3-phosphonates or open chain α-hydrazono phosphonates.

Synthetic Methods for Azaheterocyclic Phosphonates and Their Biological Activity: An Update 2004–2024

“…This was possible by intercepting transient azovinylphosphonates, formed by base induced dehydrohalogenation of hydrazones 702, with electron rich olefins (703) and heterocycles (704 and 696) (Scheme 128). 376 5.2.6. Hydropyrimidones and Hydropyridinones.…”

Addition and Cycloaddition Reactions of Phosphinyl- and Phosphonyl-2H-Azirines, Nitrosoalkenes and Azoalkenes

“…The nitrogen heteroaromatic N -methylimidazole was reported to promote dehydrohalogenation of hydrazone 87 and to add regioselectively to the azo-alkene 89 , conducting to functionalized α -hydrazonophosphonate 91 [ 51 ] ( Scheme 24 ).…”

“…Cycloadducts were also obtained in regioselective fashion in reactions of azoalkenes bearing a phosphonate substituent at the 3-position with electron rich olefins [ 51 ] ( Scheme 28 ).…”

Chemoselective reaction of ethane-1,2-dithiol, hydrazines, and hydroxylamine onto γ-keto allyl phosphonates and phosphine oxides

“…[2][3][4] For this purpose, we first envisioned, without prior protection of the ketone moiety, [5][6] their deprotonation with an excess of strong bases including LDA and NaH then the trapping of the intermediate enolates with various electrophiles (alkyl, alkenyl or benzyl halides, bromine, and aldehydes). [7][8][9][10] Among these reactions, we intended to particularly develop the Wittig-Horner olefination using various aldehydes as electrophiles, which would afford a variety of 1,3-dienes that are employed as useful substrates in the reaction of Diels-Alder.…”