On the direct reduction of arsonic acids to arsenoso compounds: mechanisms and preparations

Abstract

By using a variety of reducing agents, either alone or in the presence of iodide as a catalyst, the reduction of arsonic acids to arsenoso compounds and/or arsonous acids has been studied. The solvent and temperature are important for a clean reduction. The mechanism of the reduction involves prior protonation of the AsO3H2 group, and can be rationalized in the framework of the ‘hard and soft acids and bases’ principle, which is used to predict other reducing systems and to explain other literature data. For preparative purposes, triphenylphosphine/iodine, hexamethylphosphorous triamide/iodine and ascorbic acid/iodine give flexibility of choice depending on the substrate. The first two of these systems decompose arsonic acids with a weak C–As bond but the last system is sufficiently mild towards the same arsonic acids. Copyright © 2000 John Wiley & Sons, Ltd.

Syntheses of arsinolipids: non-isosteric analogues of phospholipids

“…The 1 H NMR spectrum of 7b showed three peaks for the CH 2 OH and two peaks for the CH 2 As groups. 13 The product 9b showed these absorptions at the expected d values (3.51 and 2.56, respectively), which are the same as those found in the spectrum of 3. 8 In the 1 H NMR spectrum of 10b the CH 2 As(III) moves to d 2.04 in accordance with the lower electronegativity of As(III) than As(V).…”

The reduction of p-arsanilic acid (p-aminophenylarsonic acid) to its arsonous acid or arsine oxide: A case study

“…From the precipitated crude product (H 2 NPhAsO) m by column chromatography we isolated pure Ph 3 P-PhNH 2 + HO − (5%) and (H 2 NPhAsO) 4w (∼30%). Previously [19], we detected Ph 4 P + in the reduction of PhAsO 3 H 2 by Ph 3 P/I 2 which gave 87% (PhAsO) x .…”

“…The zwitterionic 1 in methanol was not reduced by equimolar amounts of Ph 3 P or (Me 2 N) 3 P in the presence of 5 mol% I 2 after 24 h stirring at RT indicating that prior protonation of the -AsO 3 H 2 to -As + (OH) 3 is required in order for the I − (the true reducing agent) to enter into the vacant site of arsenic as it was detailed previously [19]. In the case of P(III) compounds, "protonation" of the As = O group is achieved by, e.g., Ph 3 P-OMe + that in the case of 1 did not take place.…”

The reaction of L-cysteine, L-cysteine hydrochloride and glutathione with arsonolipids (2,3-diacyloxypropylarsonic acids) and their arsenoso derivatives

“…The reduction of the -AsO 3 H 2 group to -As(OH) 2 or (-AsO) x should be done in de-aerated methanol and the system ascorbic acid/iodine is chosen because the product is lipophilic [11]. The reduction can be followed by TLC (in AcOEt for ascorbic and dehydroxyascorbic acids [17] and in CHCl 3 /AcOH 10:1 for 1a - 1d and the reduction products (although the two run quite close), or by obtaining a clear solution where the reduction can be regarded as nearly completed.…”

“…In this paper three reactions have been encountered. The first is the reduction of arsonic acids 1 to their arsenoso compounds 3 by ascorbic acid in the presence of a catalytic amount of iodine and a probable mechanism has been published [11].…”