Synthesis and electronic properties of donor-acceptor pi-conjugated siloles

An efficient method is presented for the synthesis of novel donor-acceptor silole chromophores through selective monohalogenation of 2,5-dimetallosiloles followed by Negishi alkyne cross-coupling reactions. The electronic properties and crystal packing of these new siloles can be controlled through judicious combinations of peripheral functional groups.     

Material-based process-chain optimization in metal forming

The characteristics of a manufacturing product are influenced by a variety of different factors, such as the material properties of the base product. The prediction of properties that give optimal results in metal forming applications is a complex task but of high interest for the manufacturer. To realize such a prediction scheme, the process chain is split up into individual process steps and for each of them an inverse modeling is required. The specific aim of this work is to present an approach for the inverse problem formulation of a process step and to solve it using methods of machine learning. Moreover, the challenges that often arise due to the ill-posed nature of inverse problems will be discussed. The main focus is on the crystallographic texture of metals, which strongly affects the deformation behavior during a process step and highly influences the characteristics of the final product. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Gram scale synthesis of the C(18)-C(34) fragment of amphidinolide C

The synthesis of the C(18)-C(34) fragment of amphidinolide C has been achieved via two routes, culminating in both the shortest (11 steps) and highest yielding (26% overall yield) approaches to this segment. The highly convergent approach will facilitate the synthesis of analogues, including the C(18)-C(29) fragment of amphidinolide F. Synthetic highlights include the selective methylation of a diyne, and the highly efficient use of a second generation cobalt catalyst in the Mukaiyama oxidative cyclization to form the trans-THF ring.     

The formal [4+3] cycloaddition between donor-acceptor cyclobutanes and nitrones

The formal [4+3] cycloaddition of 2-alkoxy-1,1-dicarboxylate activated donor-acceptor cyclobutanes with nitrones is disclosed. The reaction forms structurally unique oxazepines in moderate to high yield with a wide scope of nitrones. In most cases either a diastereomeric mixture or a single diastereomer may be formed, depending on the reaction conditions.     

Advances in Lewis acid controlled carbon-carbon bond-forming reactions enable a concise and convergent total synthesis of bullatacin

Lewis acids control regioselectivity in the alkylation of epi-chlorohydrin and the stereochemistry of an alkyne addition to set the C24/C23 anti relationship. These advances facilitate an efficient total synthesis of bullatacin in 13.3% overall yield from commercial starting materials.     

Synthesis of Functionalized Tetrahydropyridines by SnCl4-Mediated [4+2] Cycloaddition between Donor–Acceptor Cyclobutanes and Nitriles

Cycloadditions of strained carbocycles promoted by Lewis acids are powerful methods to construct heterocyclic frameworks. In fact, the formal [3+2] cycloadditions of donor–acceptor (DA) cyclopropanes with nitriles has seen particular success in synthesis. In this work, we report on the first [4+2] cycloaddition of nitriles with DA cyclobutanes by Lewis acid activation. Tetrahydropyridine derivatives were obtained in up to 91 % yield from various aryl-activated cyclobutane diesters and aliphatic or aromatic nitriles.     

Synthesis of the C(1)-C(12) segment of peloruside A by an alpha-benzyloxymethyl ketone aldol strategy

The C(1)-C(12) segment of 16-membered antitumor macrolide peloruside A has been prepared by a BF(3).OEt(2)-catalyzed Mukaiyama aldol reaction between a glucose-derived C(1)-C(7) aldehyde and a C(8)-C(12) alpha-benzyloxymethyl ketone. Exclusive 2,3-anti and moderate 3,5-anti/syn facial selectivity (3.5:1) was observed in the aldol reaction. The key C(1)-C(7) aldehyde contains the required stereochemistry at carbons two, three, and five, and has been efficiently prepared on multigram scales from commercial triacetyl D-glucal. [reaction: see text]