No abstract

The effect of the photoinitiator branching on polymerisation thresholds in a series of triphenylamine ethyl ester derivatives is studied.

The Ni/Ir-photocatalyzed coupling of an aryl bromide (ArBr) with an alkyl bromide (RBr) has been analyzed using in situ LED-19F NMR spectroscopy. Four components (light, [ArBr], [Ni], [Ir]) are found to control the rate of ArBr consumption, but not the product selectivity, while two components ([(TMS)3SiH], [RBr]) independently control the product selectivity, but not the rate. A major resting state of nickel has been identified as ArNiII(L)­Br, and 13C-isotopic entrainment is used to show that the complex undergoes Ir-photocatalyzed conversion to products (Ar-R, Ar-H, Ar-solvent) in competition with the release of ArBr. A range of competing absorption and quenching effects lead to complex correlations between the Ir and Ni catalyst loadings and the reaction rate. Differences in the Ir/Ni Beer–Lambert absorption profiles allow the rate to be increased by the use of a shorter-wavelength light source without compromising the selectivity. A minimal kinetic model for the process allows simulation of the reaction and provides insights for optimization of these processes in the laboratory.

Research on using H-phosphonate diesters to introduce phosphorus functionality into molecules and polymers, some of which have medicinal applications, has recently attracted a lot of attention. Deuterium labelling to yield the corresponding D-phosphonate diesters, although desirable in order to help with the mechanistic elucidation of reactions containing H-phosphonate diesters, has been demonstrated to be a challenge. Deuterium exchange at Hphosphonate diesters using D 2 O, MeOD and ND 2 Bn has shown competitive behavior with hydrolysis, alcoholysis and aminolysis reactions, respectively. This facile substituent exchange for the addition of D 2 O and MeOD can be attributed to the similar energy required to eliminate ROH or H 2 O (ROD or HOD, R = iPr, Et, Me) from a pentavalent P(V) intermediate which is generated from axial delivery of an OD or OR group from D 2 O and MeOD, respectively. The trend in reaction rate for the exchange processes follows the order of R = Me > Et > iPr in (RO) 2 P(O)H and also depends on the nucleophilicity of the incoming group. Attempted synthesis of D-phosphonate diesters directly from PCl 3 and alcohols or via lithiation reactions further demonstrated just how sensitive the H/D-scrambling process is. These results have implications for the general reactivity of H-phosphonate diesters towards water, alcohol, and amines and their potential to selectively undergo substitution at either P-OR or P-H. Moreover, insight into the mechanism(s) of selective deuterium exchange, for example to give D-phosphonate diesters via the direct exchange of D for H, was illuminated through this research. at 101 MHz and are given in parts per million relative to CDCl 3 (δ = 77.0 ppm). Chemical shifts for 31 P NMR spectra are recorded at 161.97 MHz and given relative to external 85% phosphoric acid (δ = 0 ppm). Data are represented as follows: chemical shift, multiplicity (app = apparent, br = broad, s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet), coupling constants in Hertz (Hz), and integration.