Domino Heck-Aza-Michael Reactions: A One-Pot, Sequential Three-Component Approach to 1,1-Dioxido-1,2-benzisothiazoline-3-acetic Acid

Enantioselective C,P-Palladacycle-Catalyzed Arylation of Imines

Chiral diarylmethylamines are of great interest because of their prevalence in biological and pharmaceutical sciences. Herein, we report a C,P-palladacycle-catalyzed enantioselective synthesis of chiral diarylmethylamines via asymmetric arylation of N-protected imines with arylboronic acids. The C,P-palladacycle showed high reactivity (up to 99% yield) and enantioselectivity (up to 99% ee) toward this arylation, enabling the tolerance of a wide range of functionalities, providing a convenient and efficient access to enantiomerically enriched diarylmethylamines. The absolute configuration of the product was well rationalized by the proposed stereochemical pathway and the catalytical cycle.

Ruthenium(ii)-catalyzed intermolecular annulation of alkenyl sulfonamides with alkynes: access to bicyclic sultams

A ruthenium-catalyzed allylic C(sp3)-H activation strategy has been employed to develop an intermolecular coupling of alkenyl sulfonamides with alkynes. This protocol features the diastereoselective construction of [3.3.0] and [4.3.0] bicyclic sultams in one step.

Enantioselective Radical Construction of 5-Membered Cyclic Sulfonamides by Metalloradical C-H Amination

Both arylsulfonyl and alkylsulfonyl azides can be effectively activated by the cobalt(II) complexes of D₂-symmetric chiral amidoporphyrins for enantioselective radical 1,5-C-H amination to stereoselectively construct 5-membered cyclic sulfonamides. In addition to C-H bonds with varied electronic properties, the Co(II)-based metalloradical system features chemoselective amination of allylic C-H bonds and is compatible with heteroaryl groups, producing functionalized 5-membered chiral cyclic sulfonamides in high yields with high enantioselectivities. The unique profile of reactivity and selectivity of the Co(II)-catalyzed C-H amination is attributed to its underlying stepwise radical mechanism, which is supported by several lines of experimental evidence.

An N-heterocyclic carbene iridium catalyst with metal-centered chirality for enantioselective transfer hydrogenation of imines

A cyclometalating N-heterocyclic carbene iridium complex featuring metal-centered chirality was designed and used for the asymmetric transfer hydrogenation (ATH) of imines. Four strongly σ-donating carbon-based substituents (2 carbenes and 2 phenyl moieties), a chirality transfer directly from the stereogenic metal center to the C[double bond, length as m-dash]N bond of substrates, as well as a restriction of catalyst deactivation by steric demanding substituents, render the new complex one of the most efficient catalysts for ATH of cyclic N-sulfonylimines (down to 0.01 mol% cat., 24 examples, 94-98% ee).

Modular, One-Pot, Sequential Aziridine Ring Opening-S(N)Ar Strategy to 7-, 10-, and 11-Membered Benzo-Fused Sultams

The generation of common and stereochemically rich medium-sized benzo-fused sultams via complementary pairing of heretofore-unknown (o-fluoroaryl)sulfonyl aziridine building blocks with an array of amino alcohols/amines in a modular one-pot, sequential protocol using an aziridine ring opening and intramolecular nucleophilic aromatic substitution is reported. The strategy employs a variety of amino alcohols/amines and proceeds with 6 + 4/6 + 5 and 6 + 1 cycloetherification pathways in a highly chemo- and regioselective fashion to obtain skeletally and structurally diverse, polycyclic, 10- to 11- and 7-membered benzo-fused sultams for broad-scale screening.

Rh(iii)-catalyzed tandem oxidative olefination-cyclization of aryl sulfonamides

An efficient Rh(iii)-catalyzed ortho-selective C–H activation and tandem oxidative olefination-cyclization of aryl sulfonamides is described. The protocol has been applied to various substrates with good functional group tolerance.

Exploring chemical diversity via a modular reaction pairing strategy

The efficient synthesis of an 80-member library of unique benzoxathiazocine 1,1-dioxides by a microwave-assisted, intermolecular nucleophilic aromatic substitution (S_NAr) diversification pathway is reported. Eight benzofused sultam cores were generated by means of a sulfonylation/S_NAr/Mitsunobu reaction pairing protocol, and subsequently diversified by intermolecular S_NAr with ten chiral, non-racemic amine/amino alcohol building blocks. Computational analyses were employed to explore and evaluate the chemical diversity of the library.

Facile (triazolyl)methylation of MACOS-derived benzofused sultams utilizing ROMP-derived OTP reagents

A combination of MACOS scale-out and ROMP-derived oligomeric triazole phosphates (OTP(n)) have been successfully utilized for the preparation of a 106-member library of triazole containing benzothiaoxazepine-1,1-dioxides. This report demonstrates the utilization of a suite of soluble OTP(n) reagents for facile (triazolyl)methylation of 10 MACOS-derived sultam scaffolds in purification-free process for parallel synthesis of small molecule collections for HTS.

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

The synthesis of a unique isoindoline- and tetrahydroisoquinoline (THIQ)-containing tricyclic sultam library, utilizing a Heck-aza-Michael (HaM) strategy is reported. Both isoindoline and THIQ rings are installed through a Heck reaction on a vinylsulfonamide, followed by one-pot deprotection and intramolecular aza-Michael reaction. Subsequent cyclization with either paraformaldehyde condensation or 1,1'-carbonyldiimidazole coupling generates a variety of tricyclic sultams. Overall, a 160-member library of these sultams, together with their isoindolines/THIQ and secondary sulfonamides precursors, were constructed using this strategy.

Synthesis of amino-benzothiaoxazepine-1,1-dioxides utilizing a microwave-assisted, S(N)Ar protocol

The development of a microwave-assisted, intermolecular S(N)Ar protocol for the synthesis of a 126-member benzothiaoxazepine-1,1-dioxide library is reported. Diversification of 12 benzothiaoxazepine-1,1-dioxides was achieved in rapid fashion utilizing a variety of 2° amines and amino alcohols to generate an 80-member library. A second 48-member library was subsequently generated via a two-step alkylation, intermolecular S(N)Ar diversification protocol.

Amines as key building blocks in Pd-assisted multicomponent processes

In the last few years, palladium-mediated three-component synthesis has emerged as an important synthetic methodology to gain access to nitrogen-containing structures. The latest developments in this area are discussed in this review.

Triazole-containing isothiazolidine 1,1-dioxide library synthesis: one-pot, multi-component protocols for small molecular probe discovery

The construction of two libraries of triazole-containing isothiazolidine 1,1-dioxides is reported utilizing either a one-pot click/aza-Michael or click/OACC esterification protocol. One core dihydroisothiazole 1,1-dioxide scaffold was prepared rapidly on multigram scale via ring-closing metathesis (RCM) and was subjected to a one-pot multicomponent click/aza-Michael protocol with an array of amines and azides for the generation of a 180-member triazole-containing isothiazolidine 1,1-dioxide library. Alternatively, three daughter scaffolds were generated via the aza-Michael of three amino alcohols, followed by a one-pot, multicomponent click/esterification protocol utilizing a ring-opening metathesis polymerization (ROMP)-derived coupling reagent, oligomeric alkyl carbodiimide (OACC) to generate a 41-member library of triazole-containing isothiazole 1,1-dioxides.

S(N)Ar-based, facile synthesis of a library of benzothiaoxazepine-1,1'-dioxides

The construction of a library of benzothiaoxazepine-1,1'-dioxides utilizing a one-pot, S(N)Ar diversification-ODCT(50) scavenging protocol is reported. This protocol combines microwave irradiation to facilitate the reaction, in conjunction with a soluble ROMP-derived scavenger (ODCT) to afford the desired products in good overall purity. Utilizing this protocol, a 78-member library was successfully synthesized and submitted for biological evaluation.

One-pot, three-component, domino Heck-aza-Michael approach to libraries of functionalized 1,1-dioxido-1,2-benzisothiazoline-3-acetic acids

A sequential three-component synthesis of functionalized benzisothiazoline-3-acetic acid 1,1-dioxides utilizing a domino Heck-aza-Michael pathway is reported. This one-pot procedure rapidly assembles functionalized benzylsulfonamides, which undergo a palladium-catalyzed, domino, Heck-aza-Michael transformation in an experimentally straightforward manner. This attractive protocol has been utilized to synthesize three combinatorial sublibraries (I-III) comprising a total of 95 compounds in high purities (> or =95% for 75 compounds), yield and quantities.

Reagent based DOS: a "Click, Click, Cyclize" strategy to probe chemical space

The synthesis of small organic molecules as probes for discovering new therapeutic agents has been an important aspect of chemical-biology. Herein we report a reagent-based, diversity-oriented synthetic (DOS) strategy to probe chemical and biological space via a "Click, Click, Cyclize" protocol. In this DOS approach, three sulfonamide linchpins underwent cyclization protocols with a variety of reagents to yield a collection of structurally diverse S-heterocycles. In silico analysis is utilized to evaluate the diversity of the compound collection against chemical space (PC analysis), shape space (PMI) and polar surface area (PSA) calculations.

Formal [4+3] epoxide cascade reaction via a complementary ambiphilic pairing strategy

A formal [4+3] epoxide cascade protocol utilizing ambiphilic sulfonamides and a variety of epoxides (masked ambiphiles) has been developed for the generation of benzothiaoxazepine-1,1'-dioxides and oxathiazepine-1,1'-dioxides. This protocol combines an epoxide ring-opening with either an S(N)Ar or oxa-Michael cyclization pathway.

Microwave-assisted sequential one-pot protocol to benzothiadiazin-3-one-1,1-dioxides via a copper-catalyzed N-arylation strategy

A microwave-assisted, sequential, one-pot protocol has been developed for the synthesis of a variety of benzothiadiazin-3-one-1,1-dioxides. This protocol utilizes a copper-catalyzed N-arylation of α-bromo-benzenesulfonamides with a number of amines to generate the corresponding 2-aminobenzenesulfonamides, which undergo cyclization to the desired sultams using carbonyl diimidazole (CDI). A range of conditions was evaluated for the key C-N bond formation step with tolerance toward functionalized amines.

Metathesis Cascade Strategies (ROM-RCM-CM): A DOS approach to Skeletally Diverse Sultams

The development of a ring-opening metathesis/ring-closing metathesis/cross metathesis (ROM-RCM-CM) cascade strategy to the synthesis of a diverse collection of bi- and tricyclic sultams is reported. In this study, functionalized sultam scaffolds derived from intramolecular Diels-Alder (IMDA) reactions undergo metathesis cascades to yield a collection tricyclic sultams. Additional appendage based diversity was achieved by utilizing a variety of CM partners.

α-Haloarylsulfonamides: Multiple Cyclization Pathways to Skeletally Diverse Benzofused Sultams

The development of new methods to skeletally diverse sultams based on a central α-halo benzene sulfonamide building block is reported. Several salient features of this building block are utilized in multiple reaction pathways, including the Heck reaction, C- and O-arylation, Sonogashira-Pauson-Khand, Sonogashira-intramolecular hydroamination, lithiative cyclization and domino aza-Michael Heck for the generation of 5-, 6- and 7-membered benzofused bicyclic and tricyclic sultams.

"Click, click, cyclize": a DOS approach to sultams utilizing vinyl sulfonamide linchpins

A diversity-oriented synthesis (DOS) strategy termed "Click, Click, Cyclize" is reported. This approach relies on functional group (FG) pairing between a vinyl sulfonamide and an array of functional groups to synthesize skeletally diverse sultams. Several FG pairing pathways on central tertiary vinyl sulfonamide linchpins have been developed including intramolecular Heck, aza-Michael, ring-closing enyne metathesis, Pauson-Khand, and chemoselective oxidation/Baylis-Hillman reactions.