The catalytic asymmetric sulfenylation of double bonds has been achieved using a BINAM-based phosphoramide catalyst and electrophilic sulfur source. Simple alkenes as well as styrenes afforded sulfenylated tetrahydrofurans and tetrahydropyrans by closure with pendant hydroxyl or carboxyl groups. Intermolecular thiofunctionalization was also achieved with simple alcohols or carboxylic acids as the nucleophiles.
The stereocontrolled introduction of vicinal heteroatomic substituents into organic molecules is one of the most powerful ways of adding value and function. Whereas many methods exist for the introduction of oxygen- and nitrogen-containing substituents, the number stereocontrolled methods for the introduction of sulfur-containing substituents pales by comparison. Previous reports from these laboratories have described the sulfenofunctionalization of alkenes that construct vicinal carbon-sulfur and carbon-oxygen, carbon-nitrogen as well as carbon-carbon bonds with high levels of diastereospecificity and enantioselectivity. This process is enabled by the concept of Lewis base activation of Lewis acids that provides activation of Group 16 electrophiles. To provide a foundation for expansion of substrate scope and improved selectivities, we have undertaken a comprehensive study of the catalytically active species. Insights gleaned from kinetic, crystallographic and computational methods have led to the introduction of a new family of sulfenylating agents that provide significantly enhanced selectivities.
The AAA+ ATPase, p97, also referred to as VCP, plays an essential role in cellular homeostasis by regulating endoplasmic reticulumassociated degradation (ERAD), mitochondrial-associated degradation (MAD), chromatin-associated degradation, autophagy, and endosomal trafficking. Mutations in p97 have been linked to a number of neurodegenerative diseases, and overexpression of wild type p97 is observed in numerous cancers. Furthermore, p97 activity has been shown to be essential for the replication of certain viruses, including poliovirus, herpes simplex virus (HSV), cytomegalovirus (CMV), and influenza. Taken together, these observations highlight the potential for targeting p97 as a therapeutic approach in neurodegeneration, cancer, and certain infectious diseases. This Perspective reviews recent advances in the discovery of small molecule inhibitors of p97, their optimization and characterization, and therapeutic potential.
Copper oxidative addition into organohalides is a challenging two-electron process. In contrast, formal oxidative addition of copper to C sp 2 carbon− bromine bonds can be accomplished by employing latent silyl radicals under photoredox conditions. This novel paradigm for copper oxidative addition has now been applied to a Cu-catalyzed cross-coupling of C sp 3 -bromides. Specifically, a copper/photoredox dual catalytic system for the coupling of alkyl bromides with trifluoromethyl groups is presented. This operationally simple and robust protocol successfully converts a variety of alkyl, allyl, benzyl, and heterobenzyl bromides into the corresponding alkyl trifluoromethanes.
The
catalytic, enantioselective, cyclization of phenols with electrophilic
sulfenophthalimides onto isolated or conjugated alkenes affords 2,3-disubstituted
benzopyrans and benzoxepins. The reaction is catalyzed by a BINAM-based
phosphoramide Lewis base catalyst which assists in the highly enantioselective
formation of a thiiranium ion intermediate. The influence of nucleophile
electron density, alkene substitution pattern, tether length and Lewis
base functional groups on the rate, enantio- and site-selectivity
for the cyclization is investigated. The reaction is not affected
by the presence of substituents on the phenol ring. In contrast, substitutions
around the alkene strongly affect the reaction outcome. Sequential
lengthening of the tether results in decreased reactivity, which necessitated
increased temperatures for reaction to occur. Sterically bulky aryl
groups on the sulfenyl moiety prevented erosion of enantiomeric composition
at these elevated temperatures. Alcohols and carboxylic acids preferentially
captured thiiranium ions in competition with phenolic hydroxyl groups.
An improved method for the selective C(2) allylation of phenols is
also described.
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