A direct β-coupling of cyclic ketones with imines has been accomplished via the synergistic combination of photoredox catalysis and organocatalysis. Transient β-enaminyl radicals derived from ketones via enamine and oxidative photoredox catalysis readily combine with persistent α-amino radicals in a highly selective hetero radical–radical coupling. This novel pathway to γ-aminoketones is predicated upon the use of DABCO as both a base and an electron transfer agent. This protocol also formally allows for the direct synthesis of β-Mannich products via a chemoselective three-component coupling of aryl aldehydes, amines, and ketones.

Selective Radical-Radical Cross-Couplings: Design of a Formal β-Mannich Reaction.

The direct β-coupling of cyclic ketones with aryl ketones has been achieved via the synergistic combination of photoredox catalysis and organocatalysis. Diaryl oxymethyl or aryl–alkyl oxymethyl radicals, transiently generated via single-electron reduction of ketone precursors, readily merge with β-enaminyl radical species, generated by photon-induced enamine oxidation, to produce γ-hydroxyketone adducts. Experimental evidence indicates that two discrete reaction pathways can be operable in this process depending upon the nature of the ketyl radical precursor and the photocatalyst.

/pdf/direct-b-functionalization-of-cyclic-ketones-with-aryl-15zl59ewjg.pdf

Direct β‑Functionalization of Cyclic Ketones with Aryl Ketones via the Merger of Photoredox and Organocatalysis

Methods of preparation of phosphorus ylides substituted at the carbon atom of the P=C group with atoms of various elements and their application in organic synthesis are systematised and generalised The bibliography includes 508 references

https://iopscience.iop.org/article/10.1070/RC1997v066n03ABEH000232/pdf

Methods of preparation of C-substituted phosphorus ylides and their application in organic synthesis

Direct β-alkylation of saturated aldehydes has been accomplished by synergistically combining photoredox catalysis and organocatalysis. Photon-induced enamine oxidation provides an activated β-enaminyl radical intermediate, which readily combines with a wide range of Michael acceptors to produce β-alkyl aldehydes in a highly efficient manner. Furthermore, this redox-neutral, atom-economical C–H functionalization protocol can be achieved both inter- and intramolecularly. Mechanistic studies by various spectroscopic methods suggest that a reductive quenching pathway is operable.

Direct β-Alkylation of Aldehydes via Photoredox Organocatalysis

We report here the first asymmetric catalytic alkylation of unmodified ketones with alkyl halides. This metal-free approach, which requires light in order to proceed, provides a rare example of highly enantioselective photochemical catalytic processes. An easily available cinchona-based primary amine catalyst guides both the stereoselectivity-defining event and, through the transient formation of photon-absorbing chiral electron donor–acceptor complexes, the photo-activation of the substrates.

/pdf/enantioselective-direct-a-alkylation-of-cyclic-ketones-by-4vax2lwpne.pdf

Enantioselective direct α-alkylation of cyclic ketones by means of photo-organocatalysis

Some aspects of the electronic hypersurface of bis(methylene)phosphorane. An experimental and theoretical approach

The electrochemical oxidation properties of enamines of the cyclic ketones cyclo-pentanone, -hexanone, -heptanone, and -octanone with the cyclic amines pyrrolidine, piperidine, 1-methylpiperazine (1-MP), morpholine (MO), hexa-, and hepta-methyleneimine are investigated with the aid of cyclic voltammetry. The oxidations are totally irreversible. The lifetime of the intermediate cation radicals are shorter than 0.2 ms as determined by double potential step chronoamperometry. The anodic peak potentials depend on the amine component in the order of ring sizes 5 < 7; 8 < 6 < 1-MP < MO. The variation of the ketone component shows no significant influence on the peak potentials. The ionization potentials of the enamines were measured and correlated with the anodic peak potentials.

On the electrochemical oxidation of enamines

Electrochemical investigations on a selection of methylenephosphines 1 and related systems are reported. They are shown to possess an irreversible oxidation and reduction wave. An exception is diaminodiphosphene, which reversibly forms a radical anion. A relative ordering of frontier orbitals is possible, based on the redox properties of these systems.

Electrochemical investigations on methylenephosphines and related systems

The electronic properties of the title compounds are evaluated by electrochemical and quantum chemical investigations.

Bis-and Trismethylenephosphorane. Experimental and Theoretical Evaluation of Bonding Properties

BACKGROUND
Pseudoxanthoma elasticum (PXE) is a rare autosomal recessive disorder caused by mutations in the ATP-binding cassette sub-family C member 6 (ABCC6) gene. Patients with PXE show molecular and clinical characteristics of known premature aging syndromes, such as Hutchinson-Gilford progeria syndrome (HGPS). Nevertheless, PXE has only barely been discussed against the background of premature aging, although a detailed characterization of aging processes in PXE could contribute to a better understanding of its pathogenesis. Thus, this study was performed to evaluate whether relevant factors which are known to play a role in accelerated aging processes in HGPS pathogenesis are also dysregulated in PXE.


METHODS
Primary human dermal fibroblasts from healthy donors (n = 3) and PXE patients (n = 3) and were cultivated under different culture conditions as our previous studies point towards effects of nutrient depletion on PXE phenotype. Gene expression of lamin A, lamin C, nucleolin, farnesyltransferase and zinc metallopeptidase STE24 were determined by quantitative real-time polymerase chain reaction. Additionally, protein levels of lamin A, C and nucleolin were evaluated by immunofluorescence and the telomere length was analyzed.


RESULTS
We could show a significant decrease of lamin A and C gene expression in PXE fibroblasts under nutrient depletion compared to controls. The gene expression of progerin and farnesyltransferase showed a significant increase in PXE fibroblasts when cultivated in 10% fetal calf serum (FCS) compared to controls. Immunofluorescence microscopy of lamin A/C and nucleolin and mRNA expression of zinc metallopeptidase STE24 and nucleolin showed no significant changes in any case. The determination of the relative telomere length showed significantly longer telomeres for PXE fibroblasts compared to controls when cultivated in 10% FCS.


CONCLUSIONS
These data indicate that PXE fibroblasts possibly undergo a kind of senescence which is independent of telomere damage and not triggered by defects of the nuclear envelope or nucleoli deformation.

J. Niemann

Papers

Some aspects of the electronic hypersurface of bis(methylene)phosphorane. An experimental and theoretical approach

On the electrochemical oxidation of enamines

Electrochemical investigations on methylenephosphines and related systems

Bis-and Trismethylenephosphorane. Experimental and Theoretical Evaluation of Bonding Properties

The Consideration of Pseudoxanthoma Elasticum as a Progeria Syndrome.