Amphiphilic photo-isomerisable phosphanes for aqueous organometallic catalysis

Abstract

Water-soluble phosphanes were tagged with a light-responding diazo group. Upon UV exposure, the diazo-isomerisation led to phosphane morphology change, resulting in an increase in the reaction rate of an aqueous palladium-catalysed cleavage reaction.

Synthesis of Hydrophilic Phosphorus Ligands and Their Application in Aqueous‐Phase Metal‐Catalyzed Reactions

“…Afterwards the phosphine substituent was introduced at the predefined, iodinated position by a Pd‐catalyzed reaction with diphenylphosphine. Interestingly, the ligands 19 a and 19 b were shown to exhibit a lower basicity compared to the structurally similar 16 b , reflecting the electron‐withdrawing effect of the diazo group [33] . It has to be noted that the diazo group, despite its electron‐withdrawing nature, [26] is an ortho / para ‐directing substituent.…”

Photoswitchable catalysis based on the isomerisation of double bonds

“…The catalytic activity of a palladium complex of a watersoluble azobenzene-containing phosphane ligand could also be regulated by means of UV irradiation as a result of the different types of aggregates that are formed in the aqueous phase as a function of the azo-benzene geometry. 34 This was applied to regulate the rate of the palladium-catalysed cleavage of allylundecyl-carbonate in a heptane/water biphasic reaction medium.…”

Photoswitchable phosphines in catalysis

“…[15c,18] Alternatively, lithiated azobenzenes have been reacted with ClP(S)Ph 2 and the corresponding phosphines 10 have been obtained then by desulfuration with tributylphosphine (Scheme 5). [19] Palladium(II)-promoted couplings of iodo-azobenzenes with secondary phosphines (Ar 2 PH) are typified in Scheme 6 by the synthesis of phosphines bearing hydroxyl (or alkoxy) and sulfonate functions, reported by Corriu [20] and Monflier [21] respectively (Scheme 6a-b). These reactions were performed by heating the substrates mixtures at 100-135°C in the presence of Pd(OAc) 2 .…”

“…The reactions were run both in the dark and under irradiation, and parallel experiments have been conducted with the analogous biphenyl-phosphine 29, for comparison purposes (Scheme 24). [21] Overall, without UV irradiation, the presence of the diazo function has a detrimental effect on the reaction rate (entries 1,3,5 in Scheme 24). However, upon irradiation (entries 4, 6), the reaction rate increased.…”

“…Palladium(II)‐promoted couplings of iodo‐azobenzenes with secondary phosphines (Ar 2 PH) are typified in Scheme 6 by the synthesis of phosphines bearing hydroxyl (or alkoxy) and sulfonate functions, reported by Corriu [20] and Monflier [21] respectively (Scheme 6a–b). These reactions were performed by heating the substrates mixtures at 100–135 °C in the presence of Pd(OAc) 2 .…”