Synthesis of a unique isoindoline/tetrahydroisoquinoline-based tricyclic sultam library utilizing a Heck-aza-Michael strategy

Practical synthesis of isoindolines yields potent colistin potentiators for multidrug-resistant Acinetobacter baumannii

An efficient and practical one-pot synthesis of isoindolines from readily available starting materials was achieved under mild conditions by implementing an isoindole umpolung strategy. A variety of isoindolines were prepared with good to excellent yields. Biological screens of these identified compounds demonstrated that they are potent potentiators of colistin for multi-drug resistant Acinetobacter baumannii.

Synthesis of Polycyclic Isoindolines via α-C-H/N-H Annulation of Alicyclic Amines

Relatively unstable cyclic imines, generated in situ from their corresponding alicyclic amines via oxidation of their lithium amides with simple ketone oxidants, engage aryllithium compounds containing a leaving group on an ortho-methylene functionality to provide polycyclic isoindolines in a single operation. The scope of this transformation includes pyrrolidine, piperidine, azepane, azocane, and piperazines.

Synthesis of iminoisoindolinones via a cascade of the three-component Ugi reaction, palladium catalyzed isocyanide insertion, hydroxylation and an unexpected rearrangement reaction

A robust ligand-free palladium-catalyzed cascade reaction for the synthesis of diversely substituted iminoisoindolinones has been developed. The cascade reaction involves isocyanide insertion into Ugi-3CR adducts, accompanied by unexpected hydroxylation and rearrangement.

Machine-Assisted Organic Synthesis

In this Review we describe how the advent of machines is impacting on organic synthesis programs, with particular emphasis on the practical issues associated with the design of chemical reactors. In the rapidly changing, multivariant environment of the research laboratory, equipment needs to be modular to accommodate high and low temperatures and pressures, enzymes, multiphase systems, slurries, gases, and organometallic compounds. Additional technologies have been developed to facilitate more specialized reaction techniques such as electrochemical and photochemical methods. All of these areas create both opportunities and challenges during adoption as enabling technologies.

Rapid, scalable assembly of stereochemically rich, mono- and bicyclic acyl sultams

A one-pot, sequential protocol is reported that involves complementary ambiphile pairing (CAP) of a vinyl sulfonamide with a variety of unprotected amino acids via aza-Michael addition and subsequent intramolecular amidation. The method generates diverse, sp(3)-rich mono- and bicyclic acyl sultams in a highly scalable manner. Modular pairing of stereochemically rich building blocks allows quick access to all possible isomers. Extension to include one-pot, sequential 3-, 4-, and 5-multicomponent protocols is also discussed.

Parallel syntheses of eight-membered ring sultams via two cascade reactions in water

From vinyl sulfonamides as precursors to vinyl sulfonamide epoxides, two cascade reaction protocols were developed to synthesize eight-membered ring sultams in water. These protocols employ intermolecular Michael addition by NaOH or NaHS in water, followed by rapid proton transfer and intramolecular 8-endo-tet epoxide ring-opening to give medium-size sultams selectively in one-pot. Novel core structures and high synthetic efficiency make these cascade reactions highly suitable for sultam library production. Both reactions proceeded well and afforded the respective sultams in good yields under environmentally friendly conditions.

3,2-Hydroxypyridinone (3,2-HOPO) vinyl sulfonamide and acrylamide linkers: Aza-Michael addition reactions and the preparation of poly-HOPO chelators

The HOPO vinyl sulfonamide 3 and the corresponding HOPO acrylamide 10, were easily prepared by short synthetic sequences. Investigation of the aza-Michael reactions of these linkers showed that they proceed at a higher rate in solvent systems containing water. The scope and limits of the aza-Michael reactions of 3 and 10 were examined. Reagents 3 and 10 reacted cleanly with piperazine to give the corresponding adducts which were deprotected to give the di-HOPO ligands 7 and 16. Reaction of HOPO acrylamide 10 with 1,4,7-triazacyclononane gave the tris-adduct 17 which was deprotected to give the desired tris-HOPO ligand 18. Overall, the aza-Michael reactions of 3 and 10 appear to be governed not only by the solvent but also by the nature of the amine and the solubility of the reaction intermediates.

Synthesis of a Library of 1,5,2-Dithiazepine 1,1-Dioxides. Part 1: A One-Pot Sulfonylation/Thia-Michael Protocol

A novel one-pot sulfonylation/intramolecular thia-Michael protocol is reported for the synthesis of 1,5,2-dithiazepine 1,1-dioxides. Sulfonylation between cysteine ethyl ester/cysteamine and 2-chloroethanesulfonyl chloride, followed by in situ intramolecular thia-Michael addition, was achieved and afforded the titled 1,5,2-dithiazepine-1,1-dioxide scaffolds. Diversification was demonstrated for future library synthesis.

Multicapillary Flow Reactor: Synthesis of 1,2,5-Thiadiazepane 1,1-Dioxide Library Utilizing One-Pot Elimination and Inter-/Intramolecular Double aza-Michael Addition Via Microwave-Assisted, Continuous-Flow Organic Synthesis (MACOS)

A microwave-assisted, continuous-flow organic synthesis (MACOS) protocol for the synthesis of functionalized 1,2,5-thiadiazepane 1,1-dioxide library, utilizing a one-pot elimination and inter-/intramolecular double aza-Michael addition strategy is reported. The optimized protocol in MACOS was utilized for scale-out and further extended for library production using a multicapillary flow reactor. A 50-member library of 1,2,5-thiadiazepane 1,1-dioxides was prepared on a 100- to 300-mg scale with overall yields between 50 and 80% and over 90 % purity determined by proton nuclear magnetic resonance (1H-NMR) spectroscopy.

Synthesis of an Isoindoline-Annulated, Tricyclic Sultam Library via Microwave-Assisted, Continuous-Flow Organic Synthesis (MACOS)

A microwave-assisted, continuous-flow organic synthesis (MACOS) protocol for the synthesis of an isoindoline-annulat-ed, tricyclic sultam library, utilizing a Heck-aza-Michael (HaM) strategy, is reported. This sequence involves a Heck reaction on vi-nylsulfonamides with batch microwave heating followed by a one-pot, sequential intramolecular aza-Michael cyclization/Boc-deprot-ection using MACOS. Subsequent cyclization with either 1,1'-carbonyldiimidazole or chloromethyl pivalate using MACOS provided an array of tricyclic sultams. This efficient three-step protocol requires only a few hours to produce the target sultams starting from simple starting materials. Using this strategy, a 38-member library of isoindoline-annulated sultams was generated in good to excellent overall yields (53-87%).