An RCM strategy to stereodiverse delta-sultam scaffolds

Convenient Approach to Bicyclic Sultams

A method for the synthesis of aminomethyl-substituted five-membered sultams has been developed. The aminomethyl sultams were synthesized from the corresponding iodomethyl derivatives by nucleophilic substitution of the iodine atom with sodium azide followed by reduction on Pd/C. This method was further expanded to side-chain-substituted sultams, starting from amino acid esters, to obtain aminomethyl-containing bicycles. The simple practical procedure and available starting amino acid esters, including chiral examples, make various bicyclic sultams readily available.

Transition metal-free, base mediated one-pot approach for the construction of the benzo[b][1,4,5]oxathiazepine 1-oxide core

Protocol for synthesising selected separable diastereomers of benzo[b][1,4,5]oxathiazepine 1-oxides via intermolecular epoxide ring opening by o-halogenated NH-sulfoximine followed by cyclisation and configurations were assigned by 2D NMR and X-ray crystallography.

Synthesis of 3-Iodomethyl Sultams

A method for the synthesis of iodomethyl-substituted five-membered sultams has been developed. The sultams were synthesized by intramolecular iodoamination of alkenyl sulfamides. The method allows synthesis of N- and C-substituted sultams. NH-Sultams were prepared by acidic cleavage of the corresponding tert-butyl sultams that are readily available. Varying the length of alkenyl substituent at sulfamide it was shown that only five- and six-membered sultams could be prepared by this method. Neither four- nor seven-membered sultams were detected. The simple practical procedure and available starting materials make the variously substituted sultams readily available.

But-3-ene-1,3-disulfonyl difluoride (BDF): a highly selective SuFEx clickable hub for the quick assembly of sultam-containing aliphatic sulfonyl fluorides

A versatile selectively addressable SuFEx click chemistry hub, but-3-ene-1,3-disulfonyl difluoride (BDF) was designed and synthesized through head-to-tail dimerization of ethenesulfonyl fluoride (ESF). BDF possesses three active sites to selectively participate in the construction of 4-membered, 5-membered and 6-membered cyclic sulfonamide (sultams) bearing aliphatic sulfonyl fluoride moieties for further manipulations in a fast, efficient and practical manner.

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.

Synthesis of Sultams and Cyclic N-Sulfonyl Ketimines via Iron-Catalyzed Intramolecular Aliphatic C-H Amidation

Cyclic sulfonamides (sultams) play a unique role in drug discovery and synthetic chemistry. A direct synthesis of sultams by an intramolecular C(sp³)-H amidation reaction using an iron complex in situ derived from Fe(ClO₄)₂ and aminopyridine ligand is reported. This strategy features a readily available catalyst and tolerates a broad variety of substrates as demonstrated by 22 examples (up to 89% yield). A one-pot iron-catalyzed amidation/oxidation procedure for the synthesis of cyclic N-sulfonyl ketimines is also realized with up to 92% yield (eight examples). The synthetic utility of the method is validated by a gram-scale reaction and derivatization of the products to ring-fused sultams.

Palladium-catalyzed annulation of N-alkoxy benzsulfonamides with arynes by C–H functionalization: access to dibenzosultams

Palladium-catalyzed C–H/N–H functionalization of N-alkoxy benzsulfonamides with arynes provides dibenzosultams via C–C/C–N bond formation, accompanied by an unexpected N–O bond cleavage.

Application of Silica-Supported Alkylating Reagents in a One-Pot, Sequential Protocol to Diverse Benzoxathiazepine 1,1-Dioxides

Applications of silica-ROMP reagents in a one-pot, sequential protocol have been developed for the synthesis of a variety of diverse benzoxathiazepine 1,1-dioxides. This protocol includes sulfonylation, intramolecular SNAr, alkylation with silica-supported oligomeric benzyl (Si-OBPn) and triazole (Si-OTPn) phosphates, and intermolecular SNAr addition with a number of secondary amines in one-pot to afford a variety of unique benzoxathiazepine 1,1-dioxides sultams in good to excellent yields.

Synthesis of biaryl sultams using visible-light-promoted denitrogenative cyclization of 1,2,3,4-benzothiatriazine-1,1-dioxides

A novel approach has been reported for the preparation of biaryl sultams using visible-light-promoted denitrogenative cyclization of 1,2,3,4-benzothiatriazine-1,1-dioxides.

Palladium-catalyzed α-arylation of sultams with aryl and heteroaryl iodides

Palladium(0)-catalyzed conditions for the α-arylation of sultams with aryl and heteroaryl iodides have been developed. Arylation of 3-substituted 1,3-propanesultams gave rise to high yields and high diastereomeric ratios, leading to the thermodynamically favored cis product. The arylation was broadly applicable to various electron-rich and electron-poor (hetero)aromatic iodides.

Radical [3 + 2]-annulation of divinylcyclopropanes: rapid synthesis of complex meloscine analogs

A radical [3 + 2]-divinylcyclopropane annulation cascade has been extended to encompass five D-ring variants of the meloscine/epimeloscine core structure. Representative ABCD tetracyclic intermediates were further elaborated with novel substituted E-rings through subsequent transformations of advanced intermediates that provided opportunities for late-stage variation of the B-ring (lactam) N-substituents which were also developed.

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.

Total synthesis of the cytotoxic anhydrophytosphingosine pachastrissamine (jaspine B)

A short, 8-step synthesis of the marine natural product pachastrissamine has been developed that relies on a diastereoselective aldol reaction between a suitably protected hydantoin and an optically enriched α-chloroaldehyde. This synthetic route provides new opportunities for exploring structure activity relationships within this family of natural products.

Facile synthesis of benzothiadiazine 1,1-dioxides, a precursor of RSV inhibitors, by tandem amidation/intramolecular aza-Wittig reaction

Reaction of o-azidobenzenesulfonamides with ethyl carbonochloridate afforded the corresponding amide derivatives, which gave 3-ethoxy-1,2,4-benzothiadiazine 1,1-dioxides through an intramolecular aza-Wittig reaction. The reaction was found to be general through the synthesis of a number of benzothiadiazine 1,1-dioxides. Acid-catalyzed hydrolysis of 3-ethoxy-1,2,4-benzothiadiazine 1,1-dioxides furnished the 2-substituted benzothiadiazine-3-one 1,1-dioxides in good yields and high purity, which is the core moiety of RSV inhibitors.

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.

A modular reaction pairing approach to the diversity-oriented synthesis of fused- and bridged-polycyclic sultams

A reaction pairing strategy centered on utilization of a reaction triad (sulfonylation, S(N)Ar addition and Mitsunobu alkylation) generating skeletally diverse, tricyclic and bicyclic benzofused sultams is reported. Pairing sulfonylation and S(N)Ar reactions yields bridged, tricyclic and bicyclic benzofused sultams. Application of the Mitsunobu reaction in a sulfonylation-Mitsunobu-S(N)Ar pairing allows access to benzthiazocine-1,1-dioxides, while a simple change in the order of pairing to sulfonylation-S(N)Ar-Mitsunobu affords structurally different, bridged tricyclic benzofused sultams.

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.

Synthesis of epoxybenzo[d]isothiazole 1,1-dioxides via a reductive-Heck, metathesis-sequestration protocol

An atom-economical purification protocol, using solution phase processing via ring-opening metathesis polymerization (ROMP) has been developed for the synthesis of tricyclic sultams. This chromatography-free method allows for convenient isolation of reductive-Heck products and reclamation of excess starting material via sequestration involving metathesis catalysts and a catalyst-armed Si-surface.

Diversity-oriented synthesis of 13- to 18-membered macrolactams via ring-closing metathesis

An efficient build/couple/pair approach to diversity-oriented synthesis was employed to access several structurally complex macrolactams. In this paper, we describe the successful evaluation of ring-closing metathesis toward the systematic generation of skeletal diversity. By appropriately varying the nature and chain length of the alkenol fragment, a diverse collection of 13- to 18-membered macrolactams were obtained.