A method for the diastereoselective synthesis of highly substituted β-enamino ketones from anhydrides and ketone-derived imines is reported. Cyclic, enolizable anhydrides undergo a base-promoted ...conjugate addition reaction with α,β-unsaturated N-tosyl ketimines, followed by an intramolecular acylation to give formal 4 + 2 cycloaddition products. The carboxylic acid-containing products are formed with modest selectivity for the cis-diastereomer and can be fully epimerized to the trans-diastereomer upon esterification.
Results from the comprehensive fuel testing according to American Society for Testing and Materials International (ASTM) standards of an alkenone-free and decolorized biodiesel produced from the ...industrially grown marine microalgae Isochrysis sp. are presented. Fatty acid methyl ester (FAME) profiles of the non-decolorized and subsequently decolorized biodiesel fuels were nearly identical, yet the fuel properties were remarkably different. Significant positive impacts on the cetane number, kinematic viscosity, and lubricity were observed, indicating a potential deleterious effect of pigments like chlorophylls and pheophytins on these fuel properties. The decolorization process using montmorillonite K10 gave on average 90% mass recovery, and allowed for an otherwise unobtainable cloud point determination. Oxidative stability of the decolorized Isochrysis biodiesel remained well below the minimum prescribed in biodiesel standards due to elevated content of highly polyunsaturated fatty acids, however other values were in the range of those prescribed in the ASTM standards. Overall, decolorization improved the fuel properties of biodiesel from Isochrysis and may provide a path toward improved biodiesel fuels from other algal species.
Long-chain (35–40 carbons) alkenones are a unique class of lipids biosynthesized by certain species of algae including the industrially grown marine microalgae Isochrysis. Their structures are ...characterized by a very long linear carbon-chain with trans double bonds and a methyl or ethyl ketone. A method is presented for the isolation of pure alkenones from Isochrysis biomass in parallel with biodiesel production. Yields for the isolated alkenones and biodiesel relative to the starting dry Isochrysis biomass were routinely 3.5 and 12% (w/w), respectively. Alkenones were then converted to smaller hydrocarbon fragments (jet-fuel range) by cross-metathesis with 2-butene (butenolysis) using several commercial ruthenium-based metathesis initiators. Butenolysis with the second-generation Hoveyda-Grubbs catalyst occurred rapidly at 4 °C, yielding near quantitative conversion within 30 min to a mixture containing mostly 8-decen-2-one (C10), 2,9-undecadiene (C12), and 2-heptadecene (C17) as both cis- and trans isomers based on analysis by comprehensive two-dimensional gas chromatography.
Some marine microalgae, such as Isochrysis sp., produce high-melting (∼70 °C) lipids known as long-chain alkenones that detrimentally affect biodiesel fuel quality. A method has been developed for ...the production of an alkenone-free Isochrysis biodiesel. This material was prepared on sufficient scale to allow for extensive analysis according to ASTM standards. Results revealed that while cold flow improved by removal of these high-melting components and lubricity and glycerol content were below maximum levels prescribed in the standards, other properties dependent on fatty acid methyl ester (FAME) structure and composition such as oxidative stability failed to meet ASTM specifications. Both the cetane number and kinematic viscosity were lower than what would be calculated based on FAME content. This has been explained in part by 6–8% non-FAME contaminants in the tested samples.
![Formal [4 + 2] Cycloadditio...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1523-7060/small "Formal [4 + 2] Cycloadditions of Anhydrides and α,β-Unsaturated N‑Tosyl Ketimines")
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