Synthesis of Unsaturated Silyl Heterocycles an Intramolecular Silyl-Heck Reaction.

We report the synthesis of unsaturated silacycles an intramolecular silyl-Heck reaction. Using palladium catalysis, silicon electrophiles tethered to alkenes cyclize to form 5- and 6-membered silicon heterocycles. The effects of alkene substitution and tether length on the efficiency and regioselectivity of the cyclizations are described.

Reducing biomass recalcitrance by heterologous expression of a bacterial peroxidase in tobacco (Nicotiana benthamiana).

Commercial scale production of biofuels from lignocellulosic feed stocks has been hampered by the resistance of plant cell walls to enzymatic conversion, primarily owing to lignin. This study investigated whether DypB, the lignin-degrading peroxidase from Rodococcus jostii, depolymerizes lignin and reduces recalcitrance in transgenic tobacco (Nicotiana benthamiana). The protein was targeted to the cytosol or the ER using ER-targeting and retention signal peptides.

A Bench-Stable, Single-Component Precatalyst for Silyl-Heck Reactions.

Studies of the silyl-Heck reaction aimed at identifying active palladium complexes have revealed a new species that is formed in situ. This complex has been identified as the palladium iodide dimer, [(JessePhos)PdI], which has been found to be a competent single-component precatalyst for the silyl-Heck reaction. This complex is easily prepared and is temperature, moisture, and air stable.

Simplified Preparation of Trialkylvinylsilanes via the Silyl-Heck Reaction Utilizing a Second Generation Catalyst.

Recently we reported a second-generation ligand, bis(3,5-di--butylphenyl)(-butyl)phosphine, for the preparation of allyl silanes using the silyl-Heck reaction. We now show that this new ligand also provides superior reactivity in the preparation of vinylsilanes from styrene derivatives. For the first time, this new ligand provides exceptionally high yields of trialkylvinylsilanes using a widely available palladium pre-catalyst, Pd(dba).

Rational design of a second generation catalyst for preparation of allylsilanes using the silyl-Heck reaction.

Using rational ligand design, we have developed of a second-generation ligand, bis(3,5-di-tert-butylphenyl)(tert-butyl)phosphine, for the preparation of allylsilanes using the palladium-catalyzed silyl-Heck reaction. This new ligand provides nearly complete suppression of starting material alkene isomerization that was observed with our first-generation catalyst, providing vastly improved yields of allylsilanes from simple alkene starting materials. The studies quantifying the electronic and steric properties of the new ligand are described.

The First Example of Nickel-Catalyzed Silyl-Heck Reactions: Direct Activation of Silyl Triflates Without Iodide Additives.

For the first time, nickel-catalyzed silyl-Heck reactions are reported. Using simple phosphine-supported nickel catalysts, direct activation of silyl triflates has been achieved. These results contrast earlier palladium-catalyzed systems, which require iodide additives to activate silyl-triflates.

Elucidation of Diels-Alder Reaction Network of 2,5-Dimethylfuran and Ethylene on HY Zeolite Catalyst.

The reaction of 2,5-dimethylfuran and ethylene to produce p-xylene represents a potentially important route for the conversion of biomass to high-value organic chemicals. Current preparation methods suffer from low selectivity and produce a number of byproducts. Using modern separation and analytical techniques, the structure of many of the byproducts produced in this reaction when HY zeolite is employed as a catalyst has been identified.

Preparation of allyl and vinyl silanes by the palladium-catalyzed silylation of terminal olefins: a silyl-Heck reaction.

A high-yielding protocol for the palladium-catalyzed silylation of terminal alkenes using silyl halides is reported. This method allows facile conversion of styrenes to -β-silyl styrenes using either TMSI or TMSCl/LiI. Terminal allyl silanes with good ratios are also readily accessed from α-olefins by this method.

Highly brominated antimicrobial metabolites from a marine Pseudoalteromonas sp.

Extracts of a marine Pseudoalteromonas sp. (CMMED 290) isolated from the surface of a nudibranch collected in Kaneohe Bay, Oahu, displayed significant antimicrobial activity against methicillin-resistant Staphylococcus aureus. Bioassay-guided fractionation of the lipophilic extract led to the isolation and structure elucidation of two new highly brominated compounds, 2,3,5,7-tetrabromobenzofuro[3,2-b]pyrrole (1) and 4,4',6-tribromo-2,2'-biphenol (2).