György Clementis

A versatile building block for the synthesis of substituted cyclopropanephosphonic acid esters

Abstract By the effect of iodine, solid K 2 CO 3 and a lipophilic quaternary ammonium salt phosphonoacetic acid allylic esters 4 were converted to cyclopropanephosphonic acid derivatives anellated to a five membered lactone ring 6 serving as good starting material for biologically active products. The reaction of cyclopropanation has been assumed to proceed by SET induced radical type elemental steps. Direct evidences were given by ESR for the 6-endo regioselectivity in the closure of electrophilic radical 11 . An interesting and new exchange reaction of phosphonic ester moiety by iodine is also observed.

Enantioselective Synthesis of α-Alkoxy-Phosphonates by Chiral Phase Transfer Catalysis

Abstract Enantioselective PTC phosphorylation of aldehydes performed in a two phase (aq. NaOH/toluene) system mediated by chiral crown ether incorporating one or two sugar units. To avoid the rearrangement of hydroxy phosphonate 3 to nonchiral mixed phosphate ester 4 the hydroxy phosphonate was trapped by alkylation to give 5.

Scope and Limitation for the Reaction of α,β-Unsaturated Carbonyl Compounds with Phosphorus Nucleophiles by Determination of the Half-Wave Potential

Abstract During the formation of oxaphospholenes the phosphorus in the reagent gets oxidized and the double bond in the enones gets reduced.

New Synthesis of Substituted Cyclopropanephosphonic Acid Esters

Abstract Aminocyclopropane phosphonic acids are considered to be “transition state analogues” of aminocyclopropanecarboxylic acids and they may serve as enzyme inhibitors1. We attempted to synthesise aminocyclopropane derivatives by a new route2. Phosphonoacetic acid allylic esters were subjected to an intramolecular, radical cyclisation in the presence of iodine, solid potassium carbonate and phase transfer catalyst.