Jennifer J. Becker

Intermolecular Addition of Glycosyl Halides to Alkenes Mediated by Visible Light

Abstract : Catching Photons: Visible light, an amine reductant, and a Ru(bpy)32+ photocatalyst can be used to mediate the addition of glycosyl halides into alkenes to synthesize important C-glycosides. This method highlights the growing potential of photocatalysis to effectively drive useful and difficult chemical transformations.

Investigating the rate of photoreductive glucosyl radical generation.

The photoreduction of glucosyl halides to generate glucosyl radicals has been investigated to probe the nature of the photoredox cycle. Amine (the reductant) and catalyst concentration affect the reaction rate at low concentrations but exhibit saturation at higher concentrations. Water and hydrophobic catalysts were found to significantly increase the conversion efficiency.

Metal-Free Deoxygenation of Carbohydrates†

The conversion of readily available cellulosic biomass to valuable feedstocks and fuels is an attrative goal but a challenging transformation that requires the cleavage of multiple nonactivated CO bonds. Herein, the Lewis acid trispentafluorophenylborane (B(C6 F5 )3 ) is shown to catalyze the metal-free hydrosilylative reduction of monosaccharides and polysaccharides to give hydrocarbons with reduced oxygen content. The choice of the silane reductant influences the degree of deoxygenation, with diethylsilane effecting the complete reduction to produce hexanes while tertiary silanes give partially deoxygenated tetraol and triol products.

Iridium-Catalyzed Hydrosilylative Reduction of Glucose to Hexane(s)

In light of diminishing petroleum feedstocks, there is significant interest in developing carbohydrate defunctionalization reactions. In this context we have examined the use of iridium pincer catalysts for the hydrosilylative reduction of sugars, and we report herein complete reduction of silyl-protected glucose to a mixture of hexane isomers.

Terminating Platinum-Initiated Cation-Olefin Reactions with Simple Alkenes†

Abstract : The en masse cyclization of polyolefins into polycyclic terpenoids by cyclase enzymes (e.g. squalene to hopene), is a biosynthetic reaction of particular fascination to chemists. Noteworthy recent additions to synthetic mimics of the cyclase enzymes are asymmetric methods that include Br nsted Lewis acids (BLA), masked equivalents of Br+ and I+, organocatalysts, and electrophilic metal catalysts. With the exception of HgII reagents, few electrophilic metal catalysts cyclize polyenes with bio-like alkene terminators. The development of methods whose catalysts can initiate, cyclize, and terminate polyenes under ligand control would significantly advance the state of the art.

Catalytic platinum-initiated cation-olefin reactions with alkene terminating groups

A series of phosphine-Pt(2+)-catalysts is reported, which enable the oxidative cascade cyclization of poly-alkene substrates. When the terminus is appropriately arranged and a catalyst reoxidation mediator is included, several polycyclic all carbon skeletons can be obtained. In one example, a chiral P2Pt(+2) catalyst provides up to 79% ee.