Synthesis of H‐Phosphinates by the UV Light–Mediated Fragmentation‐Related Phosphorylation Using Simple P‐Heterocycles

Photolysis of aryl‐substituted 2,5‐dihydrophosphole oxides (5a–e and 8) in the presence of methanol afforded methyl aryl‐H‐phosphinates (2a–e) in good yields. In the case of 1‐ethyl‐, cyclohexyl‐, or ethoxy‐2,5‐dihydrophosphole oxides, the reaction was much slower (5f and 5h) or did not take place at all (5g). In such instances, the presence of an additional skeletal methyl group (7) or the use of the more strained 7‐phosphanorbornene derivatives (6) promoted the fragmentation‐related phosphorylations. Furthermore, the effect of the ring saturation in 8 and the possible extensions to 2‐phosphabicyclo[3.1.0]hexanes (10a and 10f), a 1,2‐dihydrophosphinine oxide (11), and a 1,2,3,4,5,6‐hexahydrophosphinine oxide (12) were also investigated. Model compounds with P‐phenyl substituent that are of sufficient ring strain (8, 10a, and 11) could be utilized well.     

Formation,Degradation, and Applications of Polyperoxides

Abstract

Even though the history and chemistry of polyperoxides is long known, they need further investigation with respect to their reactivity and applications to understand their real potential. For instance, unlike in acid polyperoxides, only scanty reports have been made on the initiating behavior of vinyl polyperoxides inspite of their well-known synthetic chemistry. Hence, it appears that there remains a significant gap between the discovery of vinyl polyperoxides and in our understanding of their role as radical initiator. This article is intended to fill this gap by ventilating the significant developments on polyperoxides, which are finding an increasing role both in fundamental and applied polymer science. However, the scope of this article is restricted to their synthetic methodologies, degradation and applications as initiators/curatives. The kinetics and mechanism of their formation and degradation have been dealt with briefly. The characteristic and notable features of the kinetics and mechanism on polyperoxide initiated polymerizations are also discussed, and some of their applications are highlighted. Emphasis has also been laid on the futuristic research trends on polyperoxides.     

The photolysis in polymer matrices of dyes containing a benzothioxanthene chromophore linked with a hindered amine

Novel dyes based on a benzothioxantheneimide chromophore covalently linked with a sterically hindered amine (HAS) were prepared and their light stability was tested in polymer matrices. The following dyes: 2-(2,2,6,6-tetramethyl-4-piperidyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTXINH) and N-alkoxy derivative 2-(1-(1′-phenylethoxy)-2,2,6,6-tetramethyl-4-piperidyl)-thioxantheno[2,1,9-dej] isoquinoline-1,3-dione (BTXINOR) were prepared. For comparison the parent dye without HAS structural unit benzothioxanthene-3,4-dicarboxylic anhydride and the N-alkyl derivative 2-(1-dodecyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTXID) and the stable nitroxyl radical 2-(1-oxo-2,2,6,6-tetramethyl-4-piperidyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTXINO) were also tested. Their spectral properties, absorption and fluorescence have been examined in polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC) and in isotactic polypropylene (PP). The light stability of these dyes and model compounds were examined in thin polymer films. The photolysis rate was monitored by UV spectroscopy and for all additives under study it was in the range 10⁻⁴–10⁻³ h⁻¹. The rate of decomposition was the lowest for the parent amine BTXINH in PMMA, PS and PVC. The rate constants of photolysis are about 10 times higher for all adducts and the lowest rate of decomposition in PP matrix was observed for BTXINOR. A distinct stabilization effect of HAS structural unit on the dye decomposition was not observed. The light stability of the dyes was more influenced by the selection of the polymer. The photolysis proceeds rather fast in PP, and moderately in PS and PVC compared to PMMA.     

Photolabile thymidine cleavable with a 532 nanometer laser

The synthesis and characterization of a novel 3′ p-hydroxyphenacyl-caged thymidine bearing a 5′ N,N-diisopropylcyanoethylphosphoramidite is presented representing a new methodology for the photoregulation of PCR and gene expression. Solid phase oligonucleotide synthesis affords a primer blocked at the 3′ position, which could function as a phototrigger for polymerase activity. The caging group exhibits quantitative photolysis in 15 s using a 532 nm green hand laser.     

Metal-Free Far-Red Light-Driven Photolysis via Triplet Fusion to Enhance Checkpoint Blockade Immunotherapy

Metal-free long-wavelength light-driven prodrug photoactivation is highly desirable for applications such as neuromodulation, drug delivery, and cancer therapy. Herein, via triplet fusion, we report on the far-red light-driven photo-release of an anti-cancer drug by coupling the boron-dipyrromethene (BODIPY)-based photosensitizer with a photocleavable perylene-based anti-cancer drug. Notably, this metal-free triplet fusion photolysis (TFP) strategy can be further advanced by incorporating an additional functional dopant, i.e. an immunotherapy medicine inhibiting the indoleamine 2,3-dioxygenase (IDO), with the far-red responsive triplet fusion pair in an air-stable nanoparticle. With this IDO inhibitor-assisted TFP system we observed efficient inhibition of primary and distant tumors in a mouse model at record-low excitation power, compared to other photo-assisted immunotherapy approaches. This metal-free TFP strategy will spur advancement in photonics and biophotonics fields.