We report a new and efficient iron oxide catalyzed cross-coupling reaction between organometallic species such as alkyl/arylmagnesium halides or organolithium species and α-hydrogen bearing cyclic aliphatic ethers via activation of C(sp(3))-H. This is the first example of iron oxide mediated direct C-C bond formation without expensive or toxic ligands.
Polystyrene-supported palladium(0) (Pd@PS) nanoparticles as a heterogeneous catalyst have been developed for caboxylation of aryl halides, alkenylsilanes, and organoboronic acids to produce the corresponding carboxylic acids with minor quantities of corresponding aldehydes using bench-stable and inexpensive oxalic acid as the C1 source under focused microwave irradiation. The close vicinity of oxalic acid to Pd@PS maintained through ionic bonding helped to produce CO2 over the catalytic surface that concurrently participated in the carboxylation reaction.
An alkene–azide 1,3‐dipolar cycloaddition between trans‐cyclooctene (TCO) and an azide‐capped hydrogel that promotes rapid gel dissolution is reported. Using an ultrashort aryl azide‐capped peptide hydrogel (PhePhe), we have demonstrated proof‐of‐concept where upon reaction with TCO, the hydrogel undergoes a gel–sol transition via 1,2,3‐triazoline degradation and 1,6‐self‐immolation of the generated aniline. The potential application of this as a general trigger in sustained drug delivery is demonstrated through release of encapsulated cargo (doxorubicin). Administration of TCO resulted in 87 % of the cargo being released in 10 h, compared to 13–14 % in the control gels. This is the first example of a potential bioorthogonal‐triggered hydrogel dissolution using a traditional click‐type reaction. This type of stimulus could be extended to other aryl azide‐capped hydrogels.
The use of inexpensive [1] raw materials and performing reactions either in a tandem [2] or sequential [3] manner has emerged as an elegant approach in organic synthesis in terms of efficiency, economy, and waste minimization. In this context, the unrivalled diversity of the transition-metalcatalyzed reactions has made them important mediators for the elaboration of tandem processes. [2c] Notably, palladium-catalyzed Heck coupling [4] between an olefin [4a] and aryl halide (or its surrogates) [4b,c] has garnered significant attention for generating numerous biologically active stilbenoids like resveratrol, [4d] pterostilbene, [4e] etc. However, one of the coupling partners, that is, styrene, is inevitably prone to polymerization, difficult to synthesize, and tricky to purify. To counteract this problem, generation of styrene [5] in situ (by Knoevenagel decarboxylation, [5a-c] Hunsdiecker, [5d] Wittig-Horner, [5e] dehydrohalogenation Heck [5f]
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