Facile reduction of aryl halides with a combination of 5% Pd/C, B2(OH)4, and 4‐methylmorpholine is reported. Aryl bromides, iodides, and chlorides were efficiently reduced. Aryl dihalides containing two different halogen atoms underwent selective reduction: I over Br and Cl, and Br over Cl. Beyond these, aryl triflates were efficiently reduced. This combination was broadly general, effectuating reductions of benzylic halides and ethers, alkenes, alkynes, aldehydes, and azides, as well as for N‐Cbz deprotection. A cyano group was unaffected, but a nitro group and a ketone underwent reduction to a low extent. When B2(OD)4 was used for aryl halide reduction, a significant amount of deuteriation occurred. However, H atom incorporation competed and increased in slower reactions. 4‐Methylmorpholine was identified as a possible source of H atoms in this, but a combination of only 4‐methylmorpholine and Pd/C did not result in reduction. Hydrogen gas has been observed to form with this reagent combination. Experiments aimed at understanding the chemistry led to the proposal of a plausible mechanism and to the identification of N,N‐bis(methyl‐d3)pyridin‐4‐amine (DMAP‐d6) and B2(OD)4 as an effective combination for full aromatic deuteriation.

1,4‐Triazolyl combretacoumarins have been prepared by linking the trimethoxyarene unit of combretastatin A4 with coumarins, via a 1,2,3‐triazole. For this, 4‐azidocoumarins were accessed by a sequential two‐step, one‐pot reaction of 4‐hydroxycoumarins with (benzotriazol‐1‐yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP), followed by reaction with NaN3. In the reaction with BOP, a coumarin‐derived phosphonium ion intermediate seems to form, leading to an O4‐(benzotriazolyl)coumarin derivative. For the CuAAC reaction of azidocoumarins with 5‐ethynyl‐1,2,3‐trimethoxybenzene, catalytic [(MeCN)4Cu]PF6 in CH2Cl2/MeOH with 2,6‐lutidine, at 50 oC, was suitable. The 4‐azidocoumarins were less reactive as compared to PhN3 and the NBO coefficients of the azido groups were compared by DFT analysis. Compound solubility was a problem in biological assays. On the basis of the biological and solubility data of one 1,4‐triazolyl combretacoumarin, four analogs lacking one or two methoxy groups were synthesized. Reactivity differences among the phenylacetylenes were noted and the NBO coefficients of the alkynes were compared by DFT analysis. In cytotoxicity assays, 1‐phenyl‐4‐(3,4,5‐trimethoxyphenyl)‐1H‐1,2,3‐triazole showed activity in CEM and MDA‐MB‐231 cell lines by apoptosis. The desmethoxy 6‐bromo‐4‐(4‐(4‐methoxyphenyl)‐1H‐1,2,3‐triazol‐1‐yl)‐2H‐chromen‐2‐one also showed cytotoxicity against the two cell lines, but this did not appear to be consistent with apoptosis. The antiviral activity of the compounds was unremarkable.

TBDMS (t-BuMe2Si, t-butyldimethylsilyl) ethers of a variety of phenols have been deprotected with KHF2 in MeOH, at room temperature. Carboxylic ester and labile phenolic acetate were unaffected under these conditions. In competition reactions between TBDMS ethers of a phenol and two primary benzylic alcohols, the phenolic ether underwent cleavage whereas the alcohol ethers remained intact. From a substrate containing both a phenolic hydroxyl group and a secondary, doubly benzylic hydroxyl group protected as TBDMS ethers, the phenol was rapidly and selectively released. Cleavage of TBDMS, TBDPS, and TIPS ethers of a phenol was also compared. TBDMS and TBDPS ethers underwent cleavage at room temperature within 30 min, whereas removal of the TIPS ether required 2.5 hours. Ease of cleavage appears to be TBDMS ≈ TBDPS > TIPS. At 60 °C, TBDMS ethers of primary benzylic, allylic, and unactivated alcohols can be efficiently desilylated over a prolonged period (13–17 h). Thus, KHF2 proves to be a mild and effective reagent for the selective desilylation of phenol TBDMS ethers at room temperature.

The inside cover picture, designed by Lakshman and co‐workers, illustrates a diverse set of hydrogenations that can be conducted without use of external hydrogen gas (compressed gas). 4‐Methylmorpholine (NMM), tetrahydroxydiboron [B2(OH)4], and 5% Pd on charcoal work in concert to cause reductions of aryl halides and triflates, alkenes, alkynes, aldehydes, and azides, as well as cleavage of benzylic ethers and N‐Cbz groups. Based on the mechanistic knowledge gained in the study, aromatic deuteriations have also been accomplished using N,N‐bis(methyl‐d3)pyridin‐4‐amine (DMAP‐d6) and B2(OD)4. H2 gas appears to be formed in these reactions and this has been observed by 1H NMR and GC analysis. Details of this work can in found in the full paper on pages 166–176 (K. A. Korvinson, H. K. Akula, C. T. Malinchak, D. Sebastian, W. Wei, T. A. Khandaker, M. R. Andrzejewska, B. Zajc, M. K. Lakshman, Adv. Synth. Catal. 2020, 362, 166–176; DOI: 10.1002/adsc.201901099).