Sulfoximine‐Directed Arene ortho ‐Lithiation

Syntheses of Sulfilimines by Iron-Catalyzed Iminations of Sulfides with 2,2,2-Trichloroethyl Sulfamate

N-protected sulfilimines are prepared by imination of sulfides with a combination of 2,2,2-trichloroethyl sulfamate (H2NTces), (diacetoxyiodo)benzene (PIDA), and a catalytic amount of iron triflate. The reaction proceeds at room temperature, and after only 3 h a wide range of acyclic and cyclic NTces-sulfilimines with various functional groups and (hetero)aryl substituents can be obtained. By subsequent oxidation followed by deprotection, the products are converted into NH-sulfoximines.

The Versatile and Strategic O-Carbamate Directed Metalation Group in the Synthesis of Aromatic Molecules: An Update

The aryl O-carbamate (ArOAm) group is among the strongest of the directed metalation groups (DMGs) in directed ortho metalation (DoM) chemistry, especially in the form Ar-OCONEt2. Since the last comprehensive review of metalation chemistry involving ArOAms (published more than 30 years ago), the field has expanded significantly. For example, it now encompasses new substrates, solvent systems, and metalating agents, while conditions have been developed enabling metalation of ArOAm to be conducted in a green and sustainable manner. The ArOAm group has also proven to be effective in the anionic ortho-Fries (AoF) rearrangement, Directed remote metalation (DreM), iterative DoM sequences, and DoM-halogen dance (HalD) synthetic strategies and has been transformed into a diverse range of functionalities and coupled with various groups through a range of cross-coupling (CC) strategies. Of ultimate value, the ArOAm group has demonstrated utility in the synthesis of a diverse range of bioactive and polycyclic aromatic compounds for various applications.

Synthesis of Benzo[e][1,4,3]oxathiazin-3-one 1-Oxides from NH-S-(2-Hydroxyaryl)sulfoximines

Cyclizations of NH-S-(2-hydroxyaryl)sulfoximines with 1,1'-carbonyldiimidazol (CDI) give unprecedented benzo[e][1,4,3]oxathiazin-3-one 1-oxides in good yields. The standard synthetic protocol involves the use of DCE at an increased temperature for 16 h. Under mechanochemical conditions, a representative product was obtained without a solvent at ambient temperature in only 60 min. X-ray single-crystal structure analysis confirmed the molecular scaffold representing a three-dimensional heterocycle.

Crystal, Solution, and Computational Study of the Structure of Ortho-Lithium N,N-Diisopropyl-P,P-Diphenylphosphinothioic Amide

The first crystal structure of an ortho-lithium phosphinothioic amide complexed with tetramethylethylenediamine 12 is reported. The complex consists of a spirane in which the spiro-lithium is N,N- and C,S-chelated by the diamine and organophosphorus ligands, respectively. The analogous ortho anion 14 obtained by Sn(IV)/Li transmetallation in THF has also been synthesized. Nuclear magnetic resonance study of both anions showed that they exist as monomers in solution and are involved in dynamic processes including the restricted rotation around the P-N bond. 14 is converted at room temperature by nucleophilic cyclization to the dearomatized anion 15, which evolves after a few hours to the benzophosphindole sulfide 16. Density functional theory calculations supported the aggregation state in solution and were used to explore the conformational space of anion 12, the mechanism of ortho-lithiation directed by P(X)-N (X=O, S) groups, and the mechanism of formation of 15.

NMR and DFT Studies with a Doubly Labelled 15 N/6 Li S-Trifluoromethyl Sulfoximine Reveal Why a Directed ortho-Lithiation Requires an Excess of n-BuLi

This work shows why it is imperious to use an excess of butyllithium for a directed ortho-lithiation of a trifluoromethyl sulfoximine. The analysis of mixtures of n-BuLi and sulfoximine 1 in THF-d₈ using {¹ H, ⁶ Li, ¹³ C, ¹⁵ N, ¹⁹ F} NMR experiments at low temperatures reveal that a first deprotonation occurs that leads to dimeric and tetrameric N-lithiated sulfoximine (93 : 7). Using an excess n-BuLi (5 equivalents), the second deprotonation on the ortho-position of the aromatic occurs. Six species were observed and characterized on the way. It includes three aggregates involving a sulfoximine: i) a [dilithiated sulfoximine/(n-BuLi)] dimer solvated by four molecules of THF (Agg2, 39 %); ii) a [dilithiated sulfoximine/(n-BuLi)₃ ] tetramer solvated by six molecules of THF (Agg3, 39 %); iii) a [dilithiated sulfoximine/(n-BuOLi)₃ ] tetramer solvated by four molecules of THF (Agg1, 22 %). A DFT study afforded optimized solvated structures for all these aggregates, fully consistent with the NMR data.

Rh(III)-catalysed C-H/C-H cross-coupling of S-aryl sulfoximines with thiophenes: facile access to [1]benzothieno[3,2-b][1]benzothiophene (BTBT) and benzothiazines

Reported herein is rhodium-catalysed oxidative C-H/C-H cross-coupling of S-aryl sulfoximines with thiophenes via a chelation-assisted strategy, which provides an efficient approach for the construction of [1]benzothieno[3,2-b][1]benzothiophene (BTBT) and benzothiazine skeletons from easily available substrates. This protocol exhibits a good compatibility with halogen substituents, thus paving the way for further transformation to prepare various organic functional molecules. The resulting benzothiazine derivative shows a deep blue emission with Commission Internationale de 'Eclairage (CIE) coordinates of (0.15, 0.04), a high quantum yield, and a delayed fluorescence lifetime.

Transition Metal-Free Synthesis of Halobenzo[b]furans from O-Aryl Carbamates via o-Lithiation Reactions

A straightforward and transition metal-free one-pot protocol to synthesize halobenzo[b]furans has been developed employing simple and easily available starting materials such as O-aryl carbamates and alkynylsulfones. The fine-tuning of the different steps involved was key to achieving a successful one-pot procedure. Initially, a directed ortho-lithiation process, which uses the carbamate as the directed metalation group, was crucial in providing access to O-2-alkynylaryl N,N-diethyl carbamates by a direct alkynylation of the o-lithiated carbamate, with arylsulfonylalkynes as electrophilic reagents. Cyclization of the generated o-alkynylaryl carbamates was successfully accomplished through a strategy involving in situ carbamate alkaline hydrolysis under conventional heating or microwave irradiation, coupled with a subsequent heterocyclization step delivering the desired benzo[b]furans. A wide variety of new halobenzo[b]furans has been synthesized and their utility has been demonstrated by their further transformation.