Showing papers by "Christian V. Stevens published in 2011"

Electron-deficient 1- and 2-azabuta-1,3-dienes: a comprehensive survey of their synthesis and reactivity

Abstract: Electron-deficient 1- and 2-azabuta-1,3-dienes are reagents intrinsically able to provide a wide range of cyclic and acyclic N-containing building blocks. Depending on their substitution, they behave as dienes for Diels–Alder reactions, as partners for [4+1], [3+2], [2+2]-cycloadditions, for aziridinations and as electrophiles for 1,2 and 1,4-additions. Nowadays, they are a very versatile family of compounds, despite their usual instability and complex reactivity. Four decades of research in this challenging area are reviewed in this critical review: their synthetic aspects and their reactivity towards a wide range of dienophiles, dipoles and nucleophiles are described as well. The introduction focuses on their electronic properties in order to get a clear picture of their reactivity (190 references).

Gold(III) chloride catalysed synthesis of 5-alkylidene-dihydrothiazoles

Abstract: A two step synthesis of dihydrothiazoles is presented. First, the previously unknown N-propargylic dithiocarboimidates are produced in good yields from easily available, cheap starting materials. The subsequent gold catalysed ring closure is fast and efficient, leading to dihydrothiazoles through a cascade of 5-exo-dig cyclisation and 1,3-alkyl migration. The yields range from 74% to 95%.

Production of biodiesel via chemical catalytic conversion.

Abstract: The objective of this chapter is to provide an overview of the conversion of various lipid sources (edible and non-edible) into biodiesel using traditional and new technologies emphasizing the quality standards mainly dependent on the used feedstock and technology, processing and purification.

Production of biodiesel via chemical catalytic conversion

Abstract: The objective of this chapter is to provide an overview of the conversion of various lipid sources (edible and non-edible) into biodiesel using traditional and new technologies emphasizing the quality standards mainly dependent on the used feedstock and technology, processing and purification

Microreactor Technology as an Efficient Tool for Multicomponent Reactions

Abstract: Multicomponent reactions are an important tool in organic synthesis as they often allow the circumvention of multistep procedures by combining three or more molecules into one structure in a single step. An additional asset of the approach is the significant increase of the combinatorial possibilities, since a modification of the final product is easily accomplished by implementing minor changes in the reaction setup; this obviously allows considerable savings in time and resources. These advantages are of particular interest in pharmaceutical research for the construction of libraries. In order to increase the sustainability of chemical processes, the field is intensively explored, and novel reactions are frequently reported. Microreactor technology also offers a contemporary way of conducting chemical reactions in a more sustainable fashion due to the miniaturization and increased safety, and also in a technically improved manner due to intensified process efficiency. This relatively new technology is implemented in novel and improved applications and is getting more and more used in chemical research. The combination of the benefits from the two approaches clearly presents an attractive reaction design, and this chapter presents an overview of the reported examples in which the microreactor technology and the multicomponent approach are combined, usually with dramatically improved results compared to those previously reported.

Synthesis of novel urethanes from a castor oil derived C22-acyloin

Abstract: The synthesis of new bio-based chemical building blocks, resulting from the condensation of a renewable C-22 acyloin derived from non-edible castor oil, with mono- and bifunctional isocyanates is reported. The condensation with aliphatic mono-isocyanates was relatively straightforward, however phenyl isocyanates only resulted in low yields together with the formation of a cyclic hemi-aminal during purification. The condensation with diisocyanates was successful for the aliphatic hexamethylene diisocyanate. As for the aromatic 2,4-toluene diisocyanate, a low yield of the desired product was obtained, since a similar ring closing reaction took place. The urethanes were synthesized in order to evaluate their plasticizing and viscosity-modifying properties.

Continuous-flow production of alkyl nitrites

Abstract: Alkyl nitrites are important building blocks for the chemical and pharmaceutical industries. In this article, we report a case study for the continuous-flow production of alkyl nitrites, originally designed by BIOS Chemicals. The intrinsic advantages of a Corning(R) Advanced-Flow T reactor system, including high versatility, high mixing, and heat-exchange efficiency under corrosive conditions, allowed the development of an economically viable and user-friendly process in a short period of time, leading to a throughput of 10t/year of processed material with high purity (93-98 percent).

Valorization of by-products for the production of biofuels

Abstract: The valorization of by-products helps to reduce waste, to minimize the footprint of the technology and to add value through the production of biodiesel as an energy carrier. Alternative resources such as deodorizer distillates can partially replace the traditional feedstocks for the production of biodiesel, but require application of new technologies and/or additional purification steps. This chapter proposes to offer an overview of different methodologies used to convert deodorized distillates to biodiesel/biofuels and to recover the valuable minor components such as sterols, squalene and tocopherols.

Synthesis of a variety of 2-alkyl-2-azabicyclo[3.1.1]heptane-1-carbonitriles via a dynamic addition-intramolecular substitution sequence

Abstract: An improved two-step synthetic approach towards 3-(2-chloroethyl) cyclobutanone is described and used in the synthesis of a class of 2-alkyl-2-azabicyclo[3.1.1]heptane-1-carbonitriles. The key step consists of a reversible addition of hydrogen cyanide onto the in situ generated imines, followed by an intramolecular nucleophilic substitution, thereby leading to the bicyclic skeleton in moderate to good yields (47-92%). These bicyclic compounds are stable, and the incorporated cyano group can be easily reduced to the corresponding aminomethyl group in high yields (93-99%), using lithium aluminum hydride.

Gold(III) Chloride Catalyzed Synthesis of 5-Alkylidene-Dihydrothiazoles.

Abstract: Starting from cheap substances, previously unknown dithiocarboimidates (IV) are prepared in good yields.

Synthesis of β‐, γ‐, δ‐, ..., ω‐Halogenated Ketones and Aldehydes

Abstract: 2.6. Radical Reactions 5932 2.6.1. Radical Halogenation 5932 2.6.2. Ring-Opening and Expansion 5932 2.6.3. Miscellaneous 5934 2.7. Ring-Opening and Ring Expansion 5934 2.7.1. Cyclic Acetals 5934 2.7.2. Epoxides 5934 2.7.3. Cycloalkanes 5935 2.7.4. Ozonides 5937 2.7.5. Ring Expansion 5938 2.8. Ring Closure and Contraction 5939 2.8.1. Ring Closure 5939 2.8.2. Ring Contraction 5943 2.8.3. Ring Rearrangements 5943 2.9. Oxidation 5943 2.9.1. Oxidation of Halogenated Alcohols 5943 2.9.2. Oxidation of Olefins 5945 2.10. Pericyclic Reactions 5945 2.10.1. Cycloadditions 5945 2.10.2. Sigmatropic Rearrangements 5945 3. Synthesis of γ-Halo Ketones and Aldehydes 5946 3.1. Nucleophilic Substitution 5946 3.1.1. Enolate Alkylation 5946 3.1.2. Conversion of an Alcohol or Ether into an Alkyl Halide 5947

Synthesis of N-Vinyl 2,2-Bisphosphonoaziridines from 1,1-Bisphosphono-2-aza-1,3-dienes.

Abstract: It is demonstrated that treatment of azadienes of type (I) and (VI) with diazomethane provides aziridines as main products.