Caged Phosphine Research Articles

A Rigid Linker for Site-Selective Coordination of Transition Metal Cations: Combining an Acetylacetone with a Caged Phosphine

The combination of a soft phosphorus and a hard oxygen donor in the new ligand HacacTRIP leads to excellent site selectivity for the coordination of two different metal cations of matching Pearson character. The deprotonation step required for coordinating the acetylacetone oxygen donor further increases the selectivity. In contrast to most phosphines, the use of the caged phosphatriptycene motif enables a rigid and directional orientation of the phosphorus binding site which is required to form stable coordination network structures. In addition to the synthesis of HacacTRIP, we present its selective coordination. The deprotonated acetylacetone was selectively bound to CuII and FeIII. The solid state structure of the former displays a rare axial coordination of chloroform molecules. The phosphorus donor was selectively coordinated to the monovalent coinage metal cations CuI, AgI, and AuI. The CuI and AgI complexes represent the first examples in which a phosphatriptycene is bound to these metal cations. Heterometallic coordination compounds were characterized with combinations of these two groups. They comprise an oligonuclear CuI/CuII mixed-valence compound in which iodide binds to both CuI and CuII cations and a complex in which acacTRIP- bridges CuII and AuI. In addition to these discrete aggregates, the ligand has been used to link FeIII and AgI into a 2D coordination polymer with unprecedented trigonal planar coordination of three bulky phosphatriptycenes to a cation and resulting honeycomb topology. Its almost regular hexagons underline the desired rigidity of the ditopic acacTRIP- ligand.

PTABS: A Unique Water-Soluble π-Acceptor Caged Phosphine

AbstractCaged phosphines have unique structures and provide many advantageous properties that can be fine-tuned to develop efficient catalytic systems. Our research group recently introduced a highly water-soluble caged phosphine: PTABS (KapdiPhos), which is a derivatized form of triazaphosphaadamantane, and explored its applicability as a strongly π-accepting ligand in combination with metals such as Pd or Cu in a variety of cross-coupling reactions of biologically relevant halonucleosides as well as chloroheteroarenes. This account details our journey from ideation to the various catalytic applications of the ligands and eventually to its commercialization.1 Introduction2 Derivatization of PTA to PTABS and Its Applications2.1 Nucleoside Modification2.2 Heteroarene Modification3 Conclusion4 Summary and Future Outlook

1,3,5-Triaza-7-phosphaadamantane (PTA) Derived Caged Phosphines for Palladium-Catalyzed Selective Functionalization of Nucleosides and Heteroarenes.

Phosphines have, in combination with transition metals, played a pivotal role in the rapid development of efficient catalytic processes. Caged phosphines constitute a class of three-dimensional scaffolds providing unique control over steric and electronic properties. The versatility of the caged phosphine ligands has been demonstrated elegantly by the groups of Verkade, Gonzalvi as well as Stradiotto. Our research group has also been working extensively for the past several years in the development of 1,3,5-triaza-7-phosphaadamantane-based caged ligands and in this personal note we have summarized these applications pertaining to the modification of biologically useful nucleosides and heteroarenes.

Scale-Up of a Heck Alkenylation Reaction: Application to the Synthesis of an Amino-Modifier Nucleoside ‘Ruth Linker’

AbstractRuth linker is a C5 pyrimidine modified nucleoside analogue widely utilized for the incorporation of a primary amine in a synthetic oligonucleotide. The increasing demand for non-radioactive labeling, detection of biomolecules, and assembly of COVID-19 test kits has triggered a need for scale-up of Ruth linker. Herein, an efficient protocol involving a palladium-catalyzed Heck alkenylation is described. The synthesis has been optimized with a goal of low catalyst concentration, column-free isolation, high product purity, reproducibility, and shorter reaction time. The scalability and utility of the process have been demonstrated successfully on a 100 g scale (starting material). Additionally, for scale-up of the Heck alkenylation protocol, 7-phospha-1,3,5-triaza-adamantanebutane sulfonate (PTABS) as the coordinating caged phosphine ligand was also synthesized on a multigram scale after careful optimization of the conditions.

ChemInform Abstract: An Exclusively trans‐Selective Chlorocarbamoylation of Alkynes Enabled by a Palladium/Phosphaadamantane Catalyst.

AbstractFor the first time, a highly efficient transition‐metal‐catalyzed atom‐economic chlorocarbamoylation reaction is reported to give access to pharmaceutically relevant methylene oxindoles, which are all obtained with E:Z selectivities <99:1.

An Exclusively trans-Selective Chlorocarbamoylation of Alkynes Enabled by a Palladium/Phosphaadamantane Catalyst.

Pharmaceutically relevant methylene oxindoles are synthesized by a palladium(0)-catalyzed intramolecular chlorocarbamoylation reaction of alkynes. A relatively underexplored class of caged phosphine ligands is uniquely suited for this transformation, enabling high levels of reactivity and exquisite trans selectivity. This report entails the first transition-metal-catalyzed atom-economic addition of a carbamoyl chloride across an alkyne.

Crystal and molecular structure of pentakis(4-methyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane)cobalt(I)(acetonitrile)trinitratocobalt(II), {Co[P(OCH2)3CMe]5}[Co(NO3)3NCMe

Unlike PR/sub 3/ ligands which readily form ONCo(PR/sub 3/)/sub 3/ upon reaction with Co(NO/sub 3/)/sub 2/ in i-PrOH, P(OCH/sub 2/)/sub 3/CMe(L) induces disproportionation of divalent cobalt to form red (CoL/sub 5/)/sub 2/Co(NO/sub 3/)/sub 4/) (1) and purple (CoL/sub 6/)/sub 2/(Co(NO/sub 3/)/sub 4/)/sub 3/ (2). Evidence for the nitrosyl complex ONCo(P(CH/sub 2/O)/sub 3/CMe)/sub 3/ (3) is presented in the case of the caged phosphine ligand, however. Attempted recrystallization of 1 from hot acetonitrile results in the formation of red (CoL/sub 5/)(Co(NO/sub 3/)/sub 3/NCMe) (4) and yellow (CoL/sub 5/)NO/sub 3/. The crystal and molecular structure of the title compound 4 was determined from three-dimensional single-crystal x-ray data. The compound crystallizes in the orthorhombic space group Pbca with a = 22.578 (3), b = 17.224 (5), and c = 25.961 (9) A and eight molecules per unit cell. The structure was solved by conventional heavy-atom techniques and refined on F by least-squares methods to weighted and unweighted R factors of 0.091 and 0.111, respectively, for 3944 independent nonzero reflections. The cation consists of a near-perfect trigonal-bipyramidal array of P atoms around the monovalent cobalt with an average CoP distance of 2.128 (3) A. Distances and angles associated with the ligand are very comparablemore » to those recently reported for P(OCH/sub 2/)/sub 3/CH/sub 2/Br. The anion has a novel heptacoordinate cobalt(II) geometry which incorporates three bidentate nitrates and an acetonitrile molecule. The axial OCoN angle is 178.9/sup 0/ while the OCoO angles in the somewhat distorted equatorial plane range from 57.9 to 93.4/sup 0/. The axial (2.160 A) and equatorial (average 2.165 A) CoO bond distances are nearly equal.« less