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

Investigating the Origin of Epimerization Attenuation during Pd-Catalyzed Cross-Coupling Reactions

Palladium-catalyzed cross-couplings remain among the most robust methodologies to form carbon-carbon and carbon-heteroatom bonds. In particular, carbon-nitrogen (C-N) couplings (Buchwald-Hartwig aminations) find widespread use in fine chemicals industries. The use of base in these reactions is critical for catalyst activation and proton sequestration. Base selection also plays an important role in process design, as strongly basic conditions can impact sensitive stereocenters and result in erosion of stereochemical purity. Herein we investigate the role of a Pd catalyst in suppressing base-mediated epimerization of a sultam stereocenter during a C-N cross-coupling reaction to access the RORγ inhibitor GDC-0022. Online high-performance liquid chromatography-mass spectrometry (HPLC-MS) was employed to acquire reaction time course profiles and to delineate epimerization behavior, identify decomposition pathways, and monitor Pd-containing species. Our ability to monitor organopalladium complexes in real time by HPLC-MS provided strong evidence that the degree of epimerization was correlated to the Pd speciation in solution. Specifically, Pd(II) complexes were associated with mitigating epimerization of six-membered sultams. Additional studies showed that the suppression of epimerization in the presence of Pd(II) can impact Pd-catalyzed reactions of other substrates such as enolizable ketones, thus providing practical insight on the execution and optimization of such processes.

One-Pot Synthesis of Polycyclic Sultams Enabled by Gold-Catalyzed Hydroamination of o-Alkynylbenzenesulfonamides and Subsequent Iodine(III)-Mediated Counteranion-Assisted Intramolecular Annulation

Herein we present a facile and efficient one-pot synthetic protocol for the construction of polycyclic sultams. This protocol involves gold-catalyzed intramolecular hydroamination of o-alkynylbenzenesulfonamides followed by HTIB-mediated counteranion-assisted intramolecular annulation. The transformation tolerates a wide range of functional groups, resulting in the formation of highly functionalized and valuable polycyclic sultam skeletons in moderate to excellent yields. These polycyclic sultams are widely used as key building blocks in organic science.

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.

Catalytic sp3 -sp3 Functionalisation of Sulfonamides: Late-Stage Modification of Drug-Like Molecules

A new application of Pd-catalysed allylation is reported that enables the synthesis of a range of branched sp³ -functionalised sulfonamides, a compound class for which few reported methods exist. By reacting benzyl sulfonamides with allylic acetates in the presence of Pd⁰ catalysts and base at room temperature, direct allylation was efficiently performed, yielding products that are analogues of structural motifs seen in biologically active small molecules. The reaction was performed under mild conditions and could be applied to nanomolar sigma-receptor binders, thus enabling a late-stage functionalisation and efficient expansion of drug-like chemical space.

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.

Palladium-Catalyzed α-Arylation of Methyl Sulfonamides with Aryl Chlorides

A Palladium-catalyzed α-arylation of sulfonamides with aryl chlorides is presented. A Buchwald type precatalyst formed with Kwong's indole-based ligand enabled this transformation to be compatible with a large variety of methyl sulfonamides and aryl chlorides in good to excellent yields. Importantly, under the optimized reaction conditions, only mono-arylated products were observed. This method has been applied to the efficient synthesis of sumatriptan, which is used to treat migraines.

Palladium Catalyzed Monoselective α-Arylation of Sulfones and Sulfonamides with 2,2,6,6-Tetramethylpiperidine·ZnCl·LiCl Base and Aryl Bromides

A palladium catalyzed Negishi-type α-arylation of sulfones and sulfonamides with a broad range of aryl bromides has been developed. The substrates are selectively metalated in situ with tmp·ZnCl·LiCl base (tmp: 2,2,6,6-tetramethylpiperidine) and cross-coupled in the presence of a catalyst system that is generated from Pd(dba)2 and XPhos. Electron-deficient, electron-rich, and heterocyclic aryl bromides have been successfully cross-coupled, and sensitive functional groups are well tolerated. Simple aryl bromides are converted overnight at 60 °C in THF while heteroaryl bromides are efficiently coupled within 2 h at 130 °C in a microwave reactor. The desired monoarylated α-branched benzyl sulfones and sulfonamides were obtained in good yields, and overarylation was not detected. The procedure is ideal for late stage functionalization in parallel medicinal chemistry.

Experimental and Computational Studies of the Diastereoselective Alkylations of 3-Substituted γ-Sultams

We report that chiral 3-substituted γ-sultam α-carbanions undergo diastereoselective alkylation reactions with alkyl halides to predominantly produce trans-3,5-disubstituted γ-sultam products. Quantum mechanical calculations provided a stereoelectronic rationale for the observed diastereoselectivity.