Acid‐Free Nickel Catalyst for Stereo‐ and Regioselective Hydrophosphorylation of Alkynes: Synthetic Procedure and Combined Experimental and Theoretical Mechanistic Study

Abstract

Abstract:The nickel catalyst prepared in situ from nickel bis(acetylacetonate) [NiA C H T U N G T R E N N U N G (acac) 2 ] precursor and bis(diphenylphosphino)ethane (DPPE) ligand has shown excellent performance in the hydrophosphorylation of alkynes. Markovnikov-type regioselective addition to terminal alkynes and stereoselective addition to internal alkynes were carried out with high selectivity without an acidic co-catalyst (in contrast to the palladium/acid catalytic system). Various Hphosphonates and alkynes reacted smoothly in the developed catalytic system with up to 99% yield. The mechanisms of catalyst activation and C À P bond formation were revealed by experimental (NMR, ESI-MS, X-ray) and theoretical (density functional calculations) studies. Two different pathways of the alkyne insertion in the coordination sphere of the metal are reported for the first time.

Development of new methods in modern selective organic synthesis: preparation of functionalized molecules with atomic precision

“…203 With this nickel complex, the catalytic reaction can be carried out without addition of the acid with no decrease in the yield or selectivity. The addition of H-phosphonates with various substituents to terminal and internal alkynes was accomplished with high regio-and stereoselectivity (Scheme 59).…”

“…The Ni(acac) 2 7dppe-based catalyst, which showed high efficiency in the hydrophosphorylation of hept-1-yne, 203 proved to be inefficient for hepta-1,6-diyne. 209 Evidently, the substantially lower reactivity of diynes compared to alkynes is due to the presence of the second triple bond in the molecule; however, the cause of this unexpected phenomenon is still unclear.…”

Recent Advances in H-Phosphonate Chemistry. Part 2. Synthesis of C-Phosphonate Derivatives

“…In these instances, Ni-and Pd-based catalysts are commonly used [184][185][186][187]. Chemical, stereochemical, and mechanistic aspects of these reactions, along with studies on the development of new catalysts, have been thoroughly covered in a recent review by Tanaka [188]; they are not the subject of this survey.…”

Recent Progress in Transition Metal-Catalyzed Addition Reactions of H–P(O) Compounds with Unsaturated Carbon Linkages

“…Nickel-catalyzed addition of H-phosphonates with alkynes was also revisited using mainly HP(O)(O i Pr) 2 and 1-heptyne [12]. Among the catalyst systems tested, the combination of [Ni(acac) 2 ] (Ni(acac) 2 can be in situ reduced to Ni(0); see [13]) and dppe appears best performing and affords branched products as major products (Scheme 4), at !100 C depending on the structures of H-phosphonate and alkyne.…”

“…A mechanism via hydropalladation shown in Scheme 11 is proposed. Hydrophosphorylation of alkynes via external attack of H-phosphonate to an (alkyne)metal complex is a possible pathway, although the possibility has been concluded to be less likely as far as the nickel-catalyzed reaction is concerned [12]. However, such a process appears to proceed in early transition metal carbonylcatalyzed reactions [19].…”