Solvent effects in the aza-Michael addition of anilines

Direct trifluoromethylselenolations of electron-rich (hetero)aromatic rings with N-trifluoromethylselenolating saccharin

A novel, easily synthesizable, shelf-stable electrophilic trifluoromethylselenolating reagent, N-trifluoromethylselenosaccharin, has been developed. This reagent can be synthesized in good yield by a two-step one-pot reaction from BnSeCF3, SO2Cl2, and silver saccharin. N-Trifluoromethylselenosaccharin proves to be an efficient trifluoromethylselenolating reagent, enabling the direct trifluoromethylselenolation of various electron-rich aromatic and heteroaromatic rings under mild reaction conditions. It exhibits excellent chemoselectivity and excellent compatibility with various functional groups, making it suitable for late-stage trifluoromethylselenolation applications in complex natural product and drug synthesis.

Domino Conjugate Addition-1,4-Aryl Migration for the Synthesis of α,β-Difunctionalized Amides

A domino difunctionalization of sulfonyl(acryl)imides to form β-substituted α-aryl amides is reported. This transformation involves a 1,4-addition followed by a polar Truce-Smiles rearrangement process, entropically driven by release of SO2. A wide range of carbon- and heteroatom-based nucleophiles and sulfonyl imides were employed, allowing rapid access to highly functionalized amides. In contrast to related reactions with a radical pathway, unbiased substrates could be employed. Despite the usual requirement of an electron-poor migrating moiety for the SNAr event, we herein report unique and unprecedented vinylogous migrations of electron-neutral arenes. Additionally, a one-pot process toward β-amido amides starting from acrylic acids has been developed.

Facile modular synthesis of jasmonoyl-l-isoleucine analogs possessing a pyrazolidin-3-one core

A short and flexible route to pyrazolidin-3-one analogs of the phytohormone (+)-7-iso-jasmonoyl-l-isoleucine is presented. The compounds were assembled from four basic building blocks, namely a pyrazolidin-3-one core, alkyl chain, linker and amino ester or acid. The efficacy of this approach was demonstrated in the synthesis of 11 analogs with variations in all parts of the molecule.

Poly(ether)s derived from oxa-Michael polymerization: a comprehensive review

Poly(ether)s represent an important class of polymers and are typically formed by ring-opening polymerization, Williamson ether synthesis, or self-condensation of alcohols. The oxa-Michael reaction presents another method to form poly(ether)s with additional functional groups in the polymer backbone starting from di- or triols and electron deficient olefins such as acrylates, sulfones, or acrylamides. However, research on oxa-Michael polymerization is still limited. Herein, we outline the principles of the oxa-Michael polymerization and focus on the synthesis and preparation of poly(ether-sulfone)s, poly(ether-ester)s, poly(ether)s, and poly(ether-amide)s. Further, challenges as well as future perspectives of the oxa-Michael polymerization are discussed.

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Optically Controlled Recovery and Recycling of Homogeneous Organocatalysts Enabled by Photoswitches

We address a critical challenge of recovering and recycling homogeneous organocatalysts by designing photoswitchable catalyst structures that display a reversible solubility change in response to light. Initially insoluble catalysts are UV-switched to a soluble isomeric state, which catalyzes the reaction, then back-isomerizes to the insoluble state upon completion of the reaction to be filtered and recycled. The molecular design principles that allow for the drastic solubility change over 10 times between the isomeric states, 87 % recovery by the light-induced precipitation, and multiple rounds of catalyst recycling are revealed. This proof of concept will open up opportunities to develop highly recyclable homogeneous catalysts that are important for the synthesis of critical compounds in various industries, which is anticipated to significantly reduce environmental impact and costs.

Hydrolytically degradable Poly (β-amino ester) resins with tunable degradation for 3D printing by projection micro-stereolithography

Applications of 3D printing that range from temporary medical devices to environmentally responsible manufacturing would benefit from printable resins that yield polymers with controllable material properties and degradation behavior. Towards this goal, poly(β-amino ester) (PBAE)-diacrylate resins were investigated due to the wide range of available chemistries and tunable material properties. PBAE-diacrylate resins were synthesized from hydrophilic and hydrophobic chemistries and with varying electron densities on the ester bond to provide control over degradation. Hydrophilic PBAE-diacrylates led to degradation behaviors characteristic of bulk degradation while hydrophobic PBAE-diacrylates led to degradation behaviors dominated initially by surface degradation and then transitioned to bulk degradation. Depending on chemistry, the crosslinked PBAE-polymers exhibited a range of degradation times under accelerated conditions, from complete mass loss in 90 min to minimal mass loss at 45 days. Patterned features with 55 μm resolution were achieved across all resins, but their fidelity was dependent on PBAE-diacrylate molecular weight, reactivity, and printing parameters. In summary, simple chemical modifications in the PBAE-diacrylate resins coupled with projection microstereolithography enables high resolution 3D printed parts with similar architectures and initial properties, but widely different degradation rates and behaviors.

Tris(2,4,6-trimethoxyphenyl)phosphine – a Lewis base able to compete with phosphazene bases in catalysing oxa-Michael reactions

The performance of the fairly airstable and commercially available “Lewis base beast” TTMPP in catalysing oxa-Michael reactions and the control of its activity by dilution and solvent choice are disclosed.

Hyperbaric reactions in organic synthesis. Progress from 2006 to 2020

This comprehensive review summarizes the published literature data concerning above 1 kbar reactions for the purposes of preparative organic synthesis (more then 50 mg of the initial substance) from 2006...

Mechanochemical Synthesis of 1,2,6-Thiadiazine 1-Oxides from Sulfonimidamides and the Fluorescence Properties of the Products

A solvent-free mechanochemical synthesis for 1,2,6-thiadiazine 1-oxides starting from NH-sulfonimidamides and propargyl ketones has been developed. Lewis acids affect these one-pot aza-Michael-addition/cyclization/dehydration reaction sequences. The photophysical properties of the resulting heterocyclic sulfonimidamide derivatives were characterized.

Catalyst-free, aza-Michael polymerization of hydrazides: polymerizability, kinetics, and mechanistic origin of an α-effect

Despite the powerful nature of the aza-Michael reaction for generating C-N linkages and bioactive moieties, the bis-Michael addition of 1° amines remains ineffective for the synthesis of functional, step-growth polymers due to the drastic reduction in reactivity of the resulting 2° amine mono-addition adduct. In this study, a wide range of commercial hydrazides are shown to effectively undergo the bis-Michael reaction with divinyl sulfone (DVS) and 1,6-hexanediol diacrylate (HDA) under catalyst-free, thermal conditions to afford moderate to high molecular weight polymers with M n = 3.8-34.5 kg mol-1. The hydrazide-Michael reactions exhibit two distinctive, conversion-dependent kinetic regimes that are 2nd-order overall, in contrast to the 3rd-order nature of amines previously reported. The mono-addition rate constant was found to be 37-fold greater than that of the bis-addition at 80 °C for the reaction between benzhydrazide and DVS. A significant majority (12 of 15) of the hydrazide derivatives used here show excellent bis-Michael reactivity and achieve >97% conversions after 5 days. This behavior is consistent with calculations that show minimal variance of electron density on the N-nucleophile among the derivatives studied. Reactivity differences between hydrazides and hexylamine are also explored. Overall, the difference in reactivity between hydrazides and amines is attributed to the adjacent nitrogen atom in hydrazides that acts as an efficient hydrogen-bond donor that facilitates intramolecular proton-transfer following the formation of the zwitterion intermediate. This effect not only activates the Michael acceptor but also coordinates with additional Michael acceptors to form an intermolecular reactant complex.

New analogs of SYA013 as sigma-2 ligands with anticancer activity

Our previous study has revealed 4-(4-(4-chlorophenyl)-1,4-diazepan-1-yl)-1-(4-fluorophenyl)butan-1-one·2HCl (SYA013) 1 as a sigma ligand with moderate selectivity for the sigma-2 receptor. Given the overexpression of sigma receptors in solid tumors and reports of sigma ligands with anticancer activities, we selected 1 for evaluation in several solid tumor cell lines. In addition, we have synthesized new analogs of 1 and now report that several of them bind preferentially at the sigma-2 receptor and have shown inhibition of several cancer cell lines including MDA-MB-231, MDA-MB-486, A549, PC-3, MIA PaCa-2 and Panc-1 cells. In particular, compounds 1 and 12 have demonstrated sub-micromolar activity against the Panc-1 cell line. It has also been observed that several of these compounds demonstrate selective toxicity toward cancer cells, when compared to normal cells.