The
design, synthesis, and development of a new class of modular,
strongly basic, and tunable bifunctional Brønsted base/H-bond-donor
organocatalysts are reported. These catalysts incorporate a triaryliminophosphorane
as the Brønsted basic moiety and are readily synthesized via
a last step Staudinger reaction of a chiral organoazide and a triarylphosphine.
Their application to the first general enantioselective organocatalytic
nitro-Mannich reaction of nitromethane to unactivated ketone-derived
imines allows the enantioselective construction of β-nitroamines
possessing a fully substituted carbon atom. The reaction is amenable
to multigram scale-up, and the products are useful for the synthesis
of enantiopure 1,2-diamine and α-amino acid derivatives.
This was the first report of a bif unctional iminophosphorane catalyzed 1,4-addition reaction as well as the f irst enantioselective sulfa-Michael addition of alkyl thiols to unactivated α-substituted acrylate esters.
The highly enantioselective sulfa-Michael addition of alkyl thiols to unactivated α-substituted acrylate esters catalyzed by a bifunctional iminophosphorane organocatalyst under mild conditions is described. The strong Brønsted basicity of the iminophosphorane moiety of the catalyst provides the necessary activation of the alkyl thiol pro-nucleophile, while the two tert-leucine residues flanking a central thiourea hydrogen-bond donor facilitate high enantiofacial selectivity in the protonation of the transient enolate intermediate. The reaction is broad in scope with respect to the alkyl thiol, the ester moiety, and the α-substituent of the α,β-unsaturated ester, affords sulfa-Michael adducts in excellent yields (up to >99%) and enantioselectivities (up to 96% ee), and is amenable to decagram scale-up using catalyst loadings as low as 0.05 mol %.
he increase in antibiotic resistance raises concerns that, at least in some regions, we are returning to a pre-antibiotic era, in particular for Gram-negative infections. The increased prevalence of extended-spectrum serine-β-lactamases (SBLs) and metallo-β-lactamases (MBLs) means β-lactams are increasingly ineffective in treating Gram-negative infections 1,2 . The advent of mobilized colistin resistance-1 in 2015 3 and transferable tigecycline resistance genes (tetX3-tetX5) in 2019 4 , which mediate resistance to colistin and tigecycline, respectively, means all clinically vital antibiotics for serious Gram-negative infections are compromised.
The highly enantioselective sulfa-Michael addition of alkyl thiols to unactivated β-substituted-α,β-unsaturated esters catalyzed by a bifunctional iminophosphorane (BIMP) organocatalyst is described.
Visible light photocatalysis allows the introduction of the sulfone functional group to anilines under mild reaction conditions, without the need for pre-functionalization.
Heteroaromatic nitriles are important compounds in drug discovery, both for their prevalence in the clinic and due to the diverse range of transformations they can undergo. As such, efficient and reliable methods to access them have the potential for far‐reaching impact across synthetic chemistry and the biomedical sciences. Herein, we report an approach to heteroaromatic C−H cyanation through triflic anhydride activation, nucleophilic addition of cyanide, followed by elimination of trifluoromethanesulfinate to regenerate the cyanated heteroaromatic ring. This one‐pot protocol is simple to perform, is applicable to a broad range of decorated 6‐ring N‐containing heterocycles, and has been shown to be suitable for late‐stage functionalization of complex drug‐like architectures.
The first enantioselective sulfa-Michael addition of alkyl thiols to alkenyl benzimidazoles, enabled by a bifunctional iminophosphorane (BIMP) organocatalyst, is described.
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