Abstract
This review describes a comprehensive account of methods which are commonly applied for the synthesis of α-heterocyclic/heteroaryl α-aminophosphonic acids and their esters. In the following order, protocols based on the methodologies listed below are discussed: (a) Pudovik reaction; (b) Kabachnik-Fields reaction and (c) Miscellaneous Methods.
Highlights
Introduction αAminophosphonic acids are considered mimics of the corresponding α-aminocarboxylic acid.[1]The phosphonic moiety has long been established as a bioisostere of a carboxylic unit
In connection with our work on the preparation of α-aminophosphonates containing heterocyclic systems,[16,17,18,19] we report in this review article all the available synthetic methods of α-heterocyclic/heteroaryl α-aminophosphonates which were published until 2013
Et 68 α-(Indol-3-yl)-α-aminophosphonate 79 was synthesized by the reaction of an aromatic amine, 3-(4-formylphenyl)indole (78) and diethyl phosphite under MW conditions in the presence of Amberlyst-15 (Scheme 33).[75]
Summary
Addition of diethyl phosphite to the azomethine bonds of the bis-Schiff base 19 was carried out, affording 1,3-bis[N-[(diethoxyphosphonyl)-(2-furyl)methyl]amino]benzene (20) In this case NMR studies revealed that the reaction product is a mixture of the two possible diastereomeric forms: R,S (meso) and the enantiomeric pair R,R and S,S (Scheme 9).[29]. Six-membered heterocycles with one heteroatom Addition of diethyl phosphite to the Schiff base 44 at room temperature without a solvent in the presence of catalytic amounts of sodium ethoxide afforded diethyl [(N-benzylamino)(2pyridinyl)methyl]phosphonate (45) which underwent acidic hydrolysis to give the corresponding α-aminophosphonic acid 46 (Scheme 17).[38]. The synthesized imines were treated with triethyl phosphite in the presence of TMSCl at room temperature to afford the corresponding diethyl α-(tetrazoloquinolin-3-yl)-α-aminophosphonate (Scheme 23).[44]. Addition of diethyl phosphite to azomethine bonds of interesting compounds 68 and 69 on fusion at 80–100 °C in the presence of a catalytic amount of triethylamine yielded one diastereomeric form of tetraethyl 5,5'-(1,4-phenylene)bis-[[[(3-oxo-3-phenyl-2,3-dihydro-4H1,2,4,3-triazaphosphol-4-yl)amino](4-oxo-4H-chromen-3-yl)methyl]phosphonate] (70) and two diastereomeric forms of tetraethyl 5,5'-(1,4-phenylene)bis-[[[(3-oxo-3-phenyl-2,3-dihydro-4H1,2,4,3-triazaphosphol-4-yl)methylphosphoryl]amino](6-methyl-4-oxo-4H-chromen-3-yl)methyl] phosphonate] (71), respectively (Scheme 27).[17]
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