Aside from life itself, phosphorus-containing compounds play crucial roles in organic synthesis, medicinal chemistry, oligonucleotide therapeutics, and materials chemistry Due to their significance, there has been a strong focus on the development of new phosphorylation reagents and methods with particular interest in P-C bond formation over the past several decades (Figure ). The formation of P-C bonds, specifically in phosphonates, has garnered significant attention in medicinal chemistry due to their chemical and enzymatic stability. Research has demonstrated that phosphonates can mimic various functional groups, such as amides, sulfoxides, sulfones, and sulfides. The isosteric replacement of an P-O bond with a P-S bond (referred to as the "thio-effect") has been shown to confer additional resistance to metabolism and, in certain instances, an increase in efficacy. The PSI-reagent platform, which is based on the P(V) oxidation state, is a useful tool for practically applying and utilizing the thio-effect (Figure ). The PSI-platform is inherently modular, comprising an initial "loading" step where phosphorus is introduced followed by a "coupling" step whereby a nucleophile is added, releasing the final P-based functional group. In its initial manifestation, various nucleophiles, such as alcohols , amines , and Grignard and organolithium reagents were utilized (guided by 2-electron logic to access P-heteroatom bonds). Shortly thereafter, the platform was further developed to add to unsaturated systems via P-centered radicals (1-electron logic) to gain access to phosphonate bonds (P-C). In that work, fully stereo-and chemoselective P(V)radical hydrophosphorylation using AIBN as a radical chain initiator was reported in contrast to methods involving metal catalysis and toxic reagents like selenium, wherein stereocontrol and chemoselectivity were low and for which further derivatization is not an option. This Communication discloses the first practical electrochemical, stereocontrolled, and chemoselective method for radical transformations of P(V) through electrochemical initiation without using radical initiators such as AIBN (Figure ). This approach allows for phosphorylation reactions (of both C=C and C=O bonds) to be carried out in a mild, rapid, and safe manner. Prior studies from this lab accessed P(V)-centered radical reactivity by heating reagent 2 at 50 ºC for >8 hours to ensure a slow decomposition of AIBN and increase the diastereomeric outcome of P-C bond formation. It was reasoned that P-centered radicals might be accessible under more industrially favorable conditions without the use of AIBN due to its relatively lower thermal stability and limitation for use on scale. A particularly promising alternative to the use of chemical radical chain initiators is electrochemical initiation, inspired by extensive research in electrochemical polymerization , which has proven to be a viable substitute for traditional polymerization techniques. The invention of a direct electrochemical hydrophosphorylation was initially explored with 4-phenyl-1-butene (1) and dihydro-Π reagent (2). Although other P(V) reagents were considered, 2, which was previously optimized and customized for P-centered radical type reactivity, was chosen for this study (Table ). In its fully optimized form, electrochemical hydrophosphorylation is relatively simple and convenient to conduct under argon in an undivided cell. To a mixture of dihydro-Π (2) (2.0 equiv.) and TBABF4 (3.0 equiv.) were added a stirred solution of TTMSS (2.5 equiv.) and DMSO (7.0 equiv.) in DCE (0.033M). Electrolysis at room temperature for 6 h delivered 3 in 81% isolated yield as a single diastereomer (d.r. >20:1, entry 1). It was found that replacing the solvent with acetonitrile lowered the yield and reduced the d.r. (entry 2), and no product was obtained while replacing the solvent with DMSO (entry 3). Next, various electrochemical parameters were explored. It was found that (+)Zn/(-)RVC in DMF gives relatively low yield (entry 4) and that using (+)Mg as an anode ablated hydrophosphorylation reactivity (entry 5). The role of DMSO in the optimized conditions is to further solubilize the electrolyte (i.e. lowering the resistance) and to serve as a source of electrons to balance the reductive fragmentation of dihydro-Π (2) (see mechanistic discussion below). Not surprisingly, rudimentary control studies (entries 6-7) demonstrated the need of TTMSS and electricity for efficient radical chain processes. Lowering the current to 0.5 mA fur-nishes the hydrophosphorylation products in slightly diminished yield (entry 8) and finally it was found that lowering the electrolyte equivalents to 1.0 equiv (instead of 3.0 equiv) form the product in lower yield and d.r. (entry 9). Interestingly, similar reactivity can be achieved using either (+)Zn/(-)RVC or (+)RVC/(-)Zn electrodes albeit with lower d.r. (entries 10-11). This observation indicated that the reaction could proceed under both reductive and oxidative conditions. In numerous experiments during the optimization phase, the formation of H-Phosphonate (36) (Fig. ) was observed as the main side product (see SI)). Thus, further investigation of the reactivity of this P-nucleophile was pursued to achieve addition across C=O bonds since "Abramov" type reactivity generally requires strong bases for nucleophilic phosphorylation (Table ). Systematic optimization for such a nucleophilic addition was conducted using 2 and 3-oxetanone. In its fully optimized form, 1,2-phosphorylation is straightforward and convenient to conduct under argon in an undivided cell. To a mixture of dihydro-Π (2) (2.0 equiv.) and KPF6 (3.0 equiv.) were added a stirred solution of TTMSS (2.5 equiv.) and ketone (1.0 equiv.) in ACN (0.033M) followed by a subsequent electrolysis at room temperature for 4-5 h resulting in a 70% isolated yield of adduct 5 (entry 1). It was found that the reaction is not sensitive to current density (15 mA) which can reduce the reaction time to 1 h (entry 2) although a lower current density was chosen for the final conditions