Evidence for cyclic azaphosphiridine oxide intermediates in the methoxide-induced rearrangements of N-alkyl α-chlorophosphonamidates: formation of phosphoramidates as well as α-aminophosphonates

Abstract

The α‐chlorophosphonamidates (I) react with the ammonium methoxide (II) to give two types of rearrangement products, the phosphoramidates (III) and the α‐amino phosphonates (IV).

Intramolecular nucleophilic catalysis and the exceptional reactivity of N-benzyloxycarbonyl α-aminophosphonochloridates

“…13 In the particular case of ClCMe 2 -P(O)(OMe)Cl we have previously seen that a nucleophile such as PhNH 2 or Bu t NH 2 may actually dealkylate the P-methoxy group by nucleophilic attack at carbon more readily than it displaces the chloride leaving group from the phosphorus atom. 12, 14 The fact that the carbamate-containing substrate 5 (X = Cl) is not less reactive than its unhindered counterpart 4 (X = Cl) is therefore diagnostically important. If the BnOCONH group were providing electrophilic catalysis of substitution (activation of the P᎐ ᎐ O group by hydrogen bonding) the rate-limiting step would still involve intermolecular nucleophilic attack at phosphorus; substitution would still be fully exposed to the effects of steric crowding, and the hindered compound 5 (X = Cl) could not possibly react so readily.…”

“…for 10 min. Volatile material was evaporated in vacuo and the residue was extracted with ether to give a mixture (18.65 g) of dimethyl 1-amino-1-methylethylphosphonate, δ P (CDCl 3 ) 34.1, δ H (CDCl 3 , 250 MHz) 3.80 (d, J PH 12, OMe) and 1.30 (d, J PH 15, Me 2 C) and the corresponding 1-hydroxy compound, δ P 29.7, δ H 3.81 (d, J PH 12) and 1.43 (d, J PH 14), in a ratio ∼ 2 : 1. A portion of the mixture (10.3 g) was dissolved in CHCl 3 (80 ml) and was stirred vigorously with NaHCO 3 (5.05 g, 60 mmol) in water (45 ml); benzyl chloroformate (8.2 g, 48 mmol) was added and stirring was continued for 1.3 h. The organic layer was collected, washed with water (2 × 50 ml) and dried (Na 2 SO 4 ).…”

The synthesis of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides by the microwave-assisted Pudovik reaction

“…As for the microwave (MW)-assisted additions, only two cases were reported, but the catalytic variations were carried out in kitchen MW ovens [32,42], and thus, do lack of exact temperatures, these results cannot be reproduced. From a ’green chemical’ point of view, the solvent-free and catalyst-free additions are of interest, however, in these reactions, relatively long reaction times (1.5–10 h), and/or unreasonably large excesses (50–150 equiv) of the dialkyl phosphite were applied [43–52]. …”