Cyclic N-sulfonyl Ketimines Research Articles

Asymmetric Organocatalyzed Reaction Sequence To Synthesize Chiral Bridged and Spiro-Bridged Benzofused Aminals via Divergent Pathways.

A highly efficient asymmetric organocatalysis-triggered reaction sequence is developed. 2-Hydroxy cinnamaldehydes and cyclic N-sulfonyl ketimines were both used as multisite substrates (more than two reactive sites) to access structurally diverse chiral bridged and spiro-bridged benzofused aminal derivatives, where an inseparable equilibrating mixture of isomers can be regioselectively converted into bridged benzofused aminals with different ring connectivities via divergent pathways. Several stereoselective transformations of the resulted bridged aminals are presented.

Diastereoselective Spirocyclization of Cyclic N-Sulfonyl Ketimines with Nitroalkenes via Iridium-Catalyzed Redox-Neutral Cascade Reaction.

An Ir(III)-catalyzed [3 + 2] annulation of weakly coordinating N-sulfonyl ketimines with challenging α, β-unsaturated nitro olefins has been achieved via redox-neutral C-H functionalization in the presence of a catalytic amount of silver hexafluoroantimonate. The generation of three consecutive stereogenic centers in a single step via direct C-H functionalization is the prime feature of this methodology. A wide array of pharmaceutically relevant nitro-substituted spirocyclic benzosultams was synthesized with good to excellent diastereoselectivity as well as in high yield starting from easily accessible substrates.

Ligand-Controlled Rhodium-Catalyzed Site-Selective Asymmetric Addition of Arylboronic Acids to α,β-Unsaturated Cyclic N-Sulfonyl Ketimines.

A site-selective rhodium-catalyzed asymmetric 1,4-/1,2-addition of arylboronic acids to challenging α,β-unsaturated cyclic ketimines was realized through a ligand-controlled strategy. By employing different chiral olefin ligands, a ligand-controlled switch in the reaction regioselectivity was attained for the first time. The reactions allow the synthesis of highly valuable α,α-disubstituted chiral allylic amines and enantioenriched 1,4-adducts. Further product transformation provided easy access to various quaternary carbon-containing chiral amines and amino acid derivatives bearing multifunctional groups.

Ir(III)/MPAA-Catalyzed Mild and Selective C-H Amidation of N-Sulfonyl Ketimines: Access To Benzosultam-Fused Quinazolines/Quinazolinones.

Ir(III)-catalyzed unprecedented mild C-H amidation for weakly coordinating cyclic N-sulfonyl ketimines, accelerated by a mono protected l-amino acid, has been developed. The method uses 1,4,2-dioxazol-5-ones as the robust amidating reagent in conjunction with a catalytic amount of silver triflate. It is highly selective and does not require a stoichiometric amount of oxidants or additives. A series of mechanistic experiments was performed to gain some insights into the reaction mechanism. The strategy provides easy access to novel benzosultam-quinazoline and benzosultam-quinazolinone hybrid scaffolds endowed with pharmaceutically relevant features.

Enantioselective [2 + 2] cycloaddition of N-allenamides with cyclic N-sulfonylketimines: access to polysubstituted azetidines bearing quaternary stereocenters.

A Ni(ClO4)2-catalyzed enantioselective [2 + 2] cycloaddition of N-allenamides with cyclic N-sulfonylketimines was developed, which regioselectively occurred at the proximal C[double bond, length as m-dash]C bonds of the N-allenamides. Broad substrate scope of N-allenamides and cyclic N-sulfonylketimines was observed. A range of fused polysubstituted azetidines bearing quaternary stereocenters were afforded in good yields and with excellent enantioselectivities (up to 99%).

Asymmetric synthesis of 4-aryl-1,2,5-thiadiazolidin-3-one 1,1-dioxides via Pd-catalyzed hydrogenation of cyclic ketimines

An efficient access to optically active sulfahydantoins, 4-aryl-1,2,5-thiadiazolidin-3-one 1,1-dioxides, was developed through palladium-catalyzed asymmetric hydrogenation of the corresponding cyclic N-sulfonylketimines with up to 98% ee.

Highly enantioselective Rh/chiral sulfur-olefin-catalyzed arylation of alkyl-substituted non-benzofused cyclic N-sulfonyl ketimines

An effective catalyst system for the highly enantioselective synthesis of α-arylalkyl-substituted sulfamidates with a quaternary stereogenic center has been developed.

Copper-catalyzed asymmetric alkynylation of cyclic N-sulfonyl ketimines.

A Cu-catalyzed asymmetric alkynylation of cyclic N-sulfonyl ketimines was developed, providing the corresponding chiral α-tertiary amines with up to 98% ee. The method tolerates some variations in cyclic N-sulfonyl ketimine and alkyne scope. These products could be used in several transformations, in particular, the products of 6-membered cyclic N-sulfonyl ketimines could be easily converted to linear chiral α-tertiary amines. This asymmetric alkynylation provides an efficient, gram-scale, low-cost transition-metal catalyzed synthesis of chiral α-tetrasubstituted propargylamines.

ChemInform Abstract: Ruthenium‐Catalyzed C—H Amidation and Alkenylation of Cyclic N‐Sulfonyl Ketimines.

A highly regioselective ruthenium-catalyzed C–H amidation of cyclic N-sulfonyl ketimines with organic sulfonyl azides is described. An alkenylation at the C–H bond of cyclic N-sulfonyl ketimines with various alkenes was also carried out. Only a catalytic amount of the oxidant Cu(OAc)2 was used in the reaction; the remainder of the required amount of oxidant was formed by regeneration of Cu(OAc)2 under an air atmosphere.

ChemInform Abstract: Construction of Cyclic Sulfamidates Bearing Two gem‐Diaryl Stereocenters Through a Rhodium‐Catalyzed Stepwise Asymmetric Arylation Protocol.

A rhodium-catalyzed stepwise asymmetric 1,4- and 1,2-addition of arylboronic acids to α,β-unsaturated cyclic N-sulfonyl ketimines has been developed, providing a wide range of gem-diaryl-substituted chiral benzosulfamidates with high optical purities. C1-Symmetric chiral diene and branched chiral sulfur–olefin ligands were sequentially utilized in this double-arylation process for high stereocontrol. Further synthetic utility offers new opportunities for the facile construction of otherwise difficult to access polycyclic heterocycles.

Construction of Cyclic Sulfamidates Bearing Two gem-Diaryl Stereocenters through a Rhodium-Catalyzed Stepwise Asymmetric Arylation Protocol.

A rhodium-catalyzed stepwise asymmetric 1,4- and 1,2-addition of arylboronic acids to α,β-unsaturated cyclic N-sulfonyl ketimines has been developed, providing a wide range of gem-diaryl-substituted chiral benzosulfamidates with high optical purities. C1-Symmetric chiral diene and branched chiral sulfur-olefin ligands were sequentially utilized in this double-arylation process for high stereocontrol. Further synthetic utility offers new opportunities for the facile construction of otherwise difficult to access polycyclic heterocycles.

Organocatalytic enantioselective Mukaiyama–Mannich reaction of fluorinated enol silyl ethers and cyclic N-sulfonyl ketimines

The first catalytic asymmetric Mukaiyama–Mannich reaction of fluorinated silyl enol ethers and ketimines is developed, allowing highly enantioselective synthesis of benzosultam based β-fluorinated Cα-tetrasubstituted α-amino acid derivatives.

Organocatalytic Enantioselective Decarboxylative Reaction of Malonic Acid Half Thioesters with Cyclic N‐Sulfonyl Ketimines by Using N‐Heteroarenesulfonyl Cinchona Alkaloid Amides

The organocatalytic enantioselective decarboxylative Mannich reaction of malonic acid half thioesters (MAHTs) with cyclic N-sulfonyl ketimines by using N-heteroarenesulfonyl cinchona alkaloid amides afforded products with high enantioselectivity. Both enantiomers of the products could be obtained by using pseudoenantiomeric chiral catalysts. The reaction proceeds through a nucleophilic addition of the MAHTs to the ketimines prior to decarboxylation.

Rhodium-catalyzed asymmetric addition of arylboronic acids to cyclic N-sulfonyl ketimines towards the synthesis of α,α-diaryl-α-amino acid derivatives.

Rhodium/chiral diene complex-catalyzed asymmetric addition of arylboronic acids to cyclic ketimines having an ester group proceeded to give the corresponding α-amino acid derivatives in high yields with high enantioselectivity. The cyclic amino acid derivative was transformed into a linear α,α-diaryl-substituted α-N-methylamino acid ester.

High performance of a palladium phosphinooxazoline catalyst in the asymmetric arylation of cyclic N-sulfonyl ketimines.

A cationic palladium complex with a chiral phosphine-oxazoline ligand (iPr-phox) showed high catalytic activity and enantioselectivity in the asymmetric addition of arylboronic acids to six-membered cyclic N-sulfonyl ketimines to give high yields of the corresponding chiral cyclic sulfamidates with 96-99.9% ee. The products have tetrasubstituted stereogenic centers with an amino group and a triaryl or alkyldiaryl group as substituents.

Aerobic oxidative C-H olefination of cyclic N-sulfonyl ketimines catalyzed by a rhodium catalyst.

A useful method for the synthesis of ortho-olefinated ketimines from readily accessible cyclic N-sulfonyl ketimines and various olefins has been achieved. The reactions proceeded by Rh(III)-catalyzed, N-sulfonyl ketimine-directed C-H cleavage under aerobic conditions. Further synthetic transformations of the olefinic products led to interesting heterocyclic molecules.

Rhodium‐Catalyzed Spirocyclic Sultam Synthesis by [3+2] Annulation with Cyclic N‐Sulfonyl Ketimines and Alkynes

Atom-economical addition: RhIII-catalyzed “Grignard-type” cyclization between cyclic N-sulfonyl ketimines and internal alkynes has been developed to afford multifunctional spirocyclic sultam products in high yields (up to 99 %) under mild conditions (see scheme, Cp* = pentamethylcyclopentadienyl, DCE = 1,2-dichloroethane).

ChemInform Abstract: Iridium‐Catalyzed [3 + 2] Annulation of Cyclic N‐Sulfonyl Ketimines with 1,3‐Dienes via C—H Activation.

Ir-catalyzed [3 + 2] annulation of cyclic N-sulfonyl ketimines with 1,3-dienes, in which an aryliridium intermediate is formed via C–H activation, gives aminoindane derivatives in high yields with high regio- and diastereoselectivity.

Iridium-Catalyzed [3 + 2] Annulation of Cyclic N-Sulfonyl Ketimines with 1,3-Dienes via C–H Activation

Ir-catalyzed [3 + 2] annulation of cyclic N-sulfonyl ketimines with 1,3-dienes, in which an aryliridium intermediate is formed via C-H activation, gives aminoindane derivatives in high yields with high regio- and diastereoselectivity.

Asymmetric Synthesis of (Triaryl)methylamines by Rhodium-Catalyzed Addition of Arylboroxines to Cyclic N-Sulfonyl Ketimines

Asymmetric addition of arylboroxines to cyclic N-sulfonyl ketimines proceeded in the presence of a rhodium catalyst coordinated with a chiral diene ligand to give high yields of benzosultams, where a triaryl-substituted stereogenic carbon center was created with high enantioselectivity (93-99% ee). The chiral benzosultams were transformed into the chiral (triaryl)methylamines by breaking the cyclic structure.