Organocatalytic Asymmetric Synthesis of Si-Stereogenic Siloxanols.

We report the organocatalytic synthesis of Si-stereogenic compounds via desymmetrization of a prochiral silanediol with a chiral imidazole-containing catalyst. This metal-free silylation method affords high yields with enantioselectivity up to 98:2 for various silanediol and silyl chloride substrate combinations (including secondary alkyl, vinyl, and H groups), accessing products with potential for further elaboration. NMR and X-ray studies reveal insight into the H-bonding interactions between the imidazole organocatalyst and the silanediol and the dual activating role of the Lewis basic imidazole to account for the high enantioselectivity.

Immobilization of Diatom with Filamentous Fungi and Its Kinetics.

Immobilizing microalgae cells in a hyphal matrix can simplify harvest while producing novel mycoalgae products with potential food, feed, biomaterial, and renewable energy applications; however, limited quantitative information to describe the process and its applicability under various conditions leads to difficulties in comparing across studies and scaling-up. Here, we demonstrate the immobilization of both active and heat-deactivated marine diatom (UTEX 466) using different loadings of fungal pellets ( sp.) and model the process through kinetics and equilibrium models.

Synthesis of Functionalized Silsesquioxane Nanomaterials by Rhodium-Catalyzed Carbene Insertion into Si-H Bonds.

We report carbene insertion into Si-H bonds of polyhedral oligomeric silsesquioxanes (POSS) for the synthesis of highly functionalized siloxane nanomaterials. Dirhodium(II) carboxylates catalyze insertion of aryl-diazoacetates as carbene precursors to afford POSS structures containing both ester and aryl groups as orthogonal functional handles for further derivatization of POSS materials. Four diverse and structurally varied silsesquioxane core scaffolds with one, three, or eight Si-H bonds were evaluated with diazo reactants to produce a total of 20 new POSS compounds.

NMR Quantification of Hydrogen-Bond-Accepting Ability for Organic Molecules.

The hydrogen-bond-accepting abilities for more than 100 organic molecules are quantified using F and P NMR spectroscopy with pentafluorobenzoic acid (PFBA) and phenylphosphinic acid (PPA) as commercially available, inexpensive probes. Analysis of pyridines and anilines with a variety of electronic modifications demonstrates that changes in NMR shifts can predict the secondary effects that contribute to H-bond-accepting ability, establishing the ability of PFBA and PPA binding to predict electronic trends. The H-bond-accepting abilities of various metal-chelating ligands and organocatalysts are also quantified.

NMR quantification of H-bond donating ability for bioactive functional groups and isosteres.

The H-bond donating ability for 127 compounds including drug fragments and isosteres have been quantified using a simple and rapid method with P NMR spectroscopy. Functional groups important to medicinal chemistry were evaluated including carboxylic acids, alcohols, phenols, thioic acids and nitrogen group H-bond donors. P NMR shifts for binding to a phosphine oxide probe have a higher correlation with equilibrium constants for H-bonding (log K) than acidity (pK), indicating that these binding experiments are representative of H-bonding ability and not proton transfer.

NMR Quantification of Halogen-Bonding Ability To Evaluate Catalyst Activity.

Quantification of halogen-bonding abilities is described for a series of benzimidazolium-, imidazolium- and bis(imidazolium) halogen-bond donors (XBDs) using P NMR spectroscopy. The measured Δδ(P) values correlate with calculated activation free energy Δ and catalytic activity for a Friedel-Crafts indole addition. This rapid method also serves as a sensitive indicator for Brønsted acid impurities.

Enantioselective Si-H Insertion Reactions of Diarylcarbenes for the Synthesis of Silicon-Stereogenic Silanes.

We report the first example of enantioselective, intermolecular diarylcarbene insertion into Si-H bonds for the synthesis of silicon-stereogenic silanes. Dirhodium(II) carboxylates catalyze an Si-H insertion using carbenes derived from diazo compounds where selective formation of an enantioenriched silicon center is achieved using prochiral silanes. Fourteen prochiral silanes were evaluated with symmetrical and prochiral diazo reactants to produce a total of 25 novel silanes.

NMR Quantification of the Effects of Ligands and Counterions on Lewis Acid Catalysis.

The relative Lewis acidity of a variety of metal-ligand catalyst complexes is quantified using P NMR spectroscopy. Three P NMR probes, including two new bidentate binding probes, are compared on the basis of different binding modes (i.e.

Catalytic Asymmetric Synthesis of Cyclopentene-spirooxindoles Bearing Vinylsilanes Capable of Further Transformations.

We report a scandium-catalyzed [3 + 2] annulation of alkylideneoxindoles with allenylsilanes for the enantioselective formation of cyclopentene-spirooxindoles containing vinylsilanes. Using a Sc(OTf)/PyBOX/BArF complex, the spiroannulation of allenylsilanes affords products with >94:6 dr and >90:10 er. The effect of the counterion and ligand to control selectivity is discussed.

Metal-Free Synthesis of 1,3-Disiloxanediols and Aryl Siloxanols.

The first example of metal-free oxidative hydrolysis of hydrido-siloxanes is reported. Both base-catalyzed and organocatalytic hydrolysis methods are demonstrated to transform 1,3-dihydrido-disiloxanes into 1,3-disiloxanediols. The first example of a chemoselective silane hydrolysis is demonstrated.

Kinetic and Binding Studies Reveal Cooperativity and Off-Cycle Competition for H-Bonding Catalysis with Silsesquioxane Silanols.

The catalytic activity, kinetics, and quantification of H-bonding ability of incompletely condensed polyhedral oligomeric silsesquioxane (POSS) silanols are reported. POSS-triols, a homogeneous model for vicinal silica surface sites, exhibit enhanced H-bonding compared with other silanols and alcohols as quantified using a P NMR probe. Evaluation of a Friedel-Crafts addition reaction shows that phenyl-POSS-triol is active as an H-bond donor catalyst whereas other POSS silanols studied are not.

Producing Oleaginous Microorganisms Using Wastewater: Methods and Guidelines for Lab- and Industrial-Scale Production.

Cultivation of oleaginous microorganisms on wastewater provides alternative biofuel options while also acting as a remediation technique for alternative wastewater treatment. This chapter describes guidelines and methods for the production of oleaginous microorganisms-with a focus on microalgae-using wastewater as a growth medium while considering a variety of general challenges for both lab- and industrial-scale production. Cultivation techniques described here range in scale from microplates with 10-mL working volumes, up to multigallon, industrial-scale microorganism cultivation, with a focus on microalgae.

Conversion of Microbial Lipids to Biodiesel and Basic Lab Tests for Analysis of Fuel-Quality Parameters.

This chapter describes lab-scale procedures for the direct conversion of microbial lipids to fatty acid methyl esters (FAMEs) for use as biodiesel fuel. Methods for the gas chromatography analysis of FAME profiles and equations to predict several fuel-quality parameters are detailed herein. This chapter also provides a complete list summarizing each of the fuel quality tests (e.

Sodium-Catalyzed Friedel-Crafts Reactions and Mechanistic Insight.

Sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBArF) demonstrates catalytic activity for Friedel-Crafts addition reactions of phenolic and other aromatic nucleophiles to trans-β-nitrostyrene. Solubility studies demonstrate a chelating effect between the Na cation and the nitro group of trans-β-nitrostyrene as the basis for catalytic activation. Mechanistic studies are presented, including a comparison with other sodium salts, additive effects, and reaction progress kinetics analysis using F NMR spectroscopy.

NMR Quantification of Hydrogen-Bond-Activating Effects for Organocatalysts including Boronic Acids.

The hydrogen-bonding activation for 66 organocatalysts has been quantified using a P NMR binding experiment with triethylphosphine oxide (TEPO). Diverse structural classes, including phenols, diols, silanols, carboxylic acids, boronic acids, and phosphoric acids, were examined with a variety of steric and electronic modifications to understand how the structure and secondary effects contribute to hydrogen-bonding ability and catalysis. Hammett plots demonstrate high correlation for the Δδ P NMR shift to Hammett parameters, establishing the ability of TEPO binding to predict electronic trends.

Reaction Progress Kinetics Analysis of 1,3-Disiloxanediols as Hydrogen-Bonding Catalysts.

1,3-Disiloxanediols are effective hydrogen-bonding catalysts that exhibit enhanced activity relative to silanediols and triarylsilanols. The catalytic activity for a series of 1,3-disiloxanediols, including naphthyl-substituted and unsymmetrical siloxanes, has been quantified and compared relative to other silanol and thiourea catalysts using the Friedel Crafts addition of indole to trans-β-nitrostyrene. An in-depth kinetic study using reaction progress kinetic analysis (RPKA) has been performed to probe the catalyst behavior of 1,3-disiloxanediols.

Synthesis of Structurally Varied 1,3-Disiloxanediols and Their Activity as Anion-Binding Catalysts.

A series of new 1,3-disiloxanediols has been synthesized, including naphthyl-substituted and unsymmetrical siloxanes, and demonstrated as a new class of anion-binding catalysts. In the absence of anions, diffusion-ordered spectroscopy (DOSY) displays self-association of 1,3-disiloxanediols through hydrogen-bonding interactions. Binding constants determined for 1,3-disiloxanediol catalysts indicate strong hydrogen-bonding and anion-binding abilities with unsymmetrical siloxanes displaying different hydrogen-bonding abilities for each silanol group.

Combined nitrogen limitation and hydrogen peroxide treatment enhances neutral lipid accumulation in the marine diatom Phaeodactylum tricornutum.

Exogenous application of dilute hydrogen peroxide (H2O2) increases neutral lipid production in Phaeodactylum tricornutum. Exposing early stationary phase cultures of P. tricornutum to 0.

Lanthanum(III)-Catalyzed Three-Component Reaction of Coumarin-3-carboxylates for the Synthesis of Indolylmalonamides and Analysis of Their Photophysical Properties.

New methodology has been developed for the Lewis acid catalyzed synthesis of malonamides. First, the scandium(III)-catalyzed addition of diverse nucleophiles (e.g.

Chlorella vulgaris production enhancement with supplementation of synthetic medium in dairy manure wastewater.

To identify innovative ways for better utilizing flushed dairy manure wastewater, we have assessed the effect of dairy manure and supplementation with synthetic medium on the growth of Chlorella vulgaris. A series of experiments were carried out to study the impacts of pretreatment of dairy wastewater and the benefits of supplementing dairy manure wastewater with synthetic medium on C. vulgaris growth increment and the ultrastructure (chloroplast, starch, lipid, and cell wall) of C.

Titanium(IV)-catalyzed stereoselective synthesis of spirooxindole-1-pyrrolines.

A stereoselective cyclization between alkylidene oxindoles and 5-methoxyoxazoles has been developed using catalytic titanium(IV) chloride (as low as 5 mol %) to afford spiro[3,3'-oxindole-1-pyrrolines] in excellent yield (up to 99%) and diastereoselectivity (up to 99:1). Using a chiral scandium(III)-indapybox/BArF complex affords enantioenriched spirooxindole-1-pyrrolines where a ligand-induced reversal of diastereoselectivity is observed. This methodology is further demonstrated for the synthesis of pyrrolines from malonate alkylidene and coumarin derivatives.

Distinct roles for mitogen-activated protein kinase signaling and CALMODULIN-BINDING TRANSCRIPTIONAL ACTIVATOR3 in regulating the peak time and amplitude of the plant general stress response.

To survive environmental challenges, plants have evolved tightly regulated response networks, including a rapid and transient general stress response (GSR), followed by well-studied stress-specific responses. The mechanisms underpinning the GSR have remained elusive, but a functional cis-element, the rapid stress response element (RSRE), is known to confer transcription of GSR genes rapidly (5 min) and transiently (peaking 90-120 min after stress) in vivo. To investigate signal transduction events in the GSR, we used a 4xRSRE:LUCIFERASE reporter in Arabidopsis (Arabidopsis thaliana), employing complementary approaches of forward and chemical genetic screens, and identified components regulating peak time versus amplitude of RSRE activity.

Catalytic enantioselective carboannulation with allylsilanes.

The first catalytic asymmetric carboannulation with allylsilanes is presented. The enantioselective [3+2] annulation is catalyzed using a scandium(III)/indapybox complex with tetrakis-[3,5-bis(trifluoromethyl)phenyl]-borate (BArF) to enhance catalytic activity and control stereoselectivity. Functionalized cyclopentanes containing a quaternary carbon center are derived from alkylidene oxindole, coumarin, and malonate substrates with high stereoselectivity.

Supramolecular hydrogen-bonding assembly of silanediols with bifunctional heterocycles.

X-ray crystallography showcases the distinct self-association and hydrogen-bonding patterns of organic silanediols, R2Si(OH)2, with bifunctional heterocycles for supramolecular assembly. Diffusion-ordered spectroscopy (DOSY) studies identify the dominant hydrogen-bonding patterns and structures in solution, which correlate with solid-state patterns at high concentrations.

Counterion effects in the catalytic stereoselective synthesis of 2,3'-pyrrolidinyl spirooxindoles.

A Lewis acid-catalyzed stereoselective [3+2] annulation of crotylsilanes with iminooxindoles is reported to access 2,3'-pyrrolidinyl spirooxindoles with four stereocenters. The addition of NaBArF significantly enhances reactivity, allowing either metal salts or acidic clay to be effective catalysts for the stereoselective reaction.