Due to the concerns over limited fossil resources and increasing CO2 emissions, there is a strong interest in use of renewable resources in production of valuable synthetic materials. PA11, 12, and 13, more commonly known as Nylon, are high-strength polymers that find use in various industrial sectors. They are traditionally produced from petroleum-derived material or exotic fatty acids using reaction sequences that involve 4-6 steps. Herein we report a simple three-step synthesis of these polyamide precursors from oleic acid, an abundant natural fatty acid available from common plant sources as well as oleaginous micro-organisms such as microalgae. This approach represents the first example where ring-closing metathesis was used for the key C-C bond forming step, featuring introduction of amine functionality required in the final product. Our versatile approach allows preparation of nylon precursors of various chain-lengths from a single starting material for economical and sustainable production of these polymers.

An oxidative amide formation using N-hydroxysuccinimide and hypervalent iodine reagents was developed. The method enables a wide range of aldehydes and amines to be coupled under mild reaction conditions providing amide in good to excellent yield. The radical species in the reaction mixture was observed for the first time using ESR measurement, and along with other mechanistic investigations, a plausible mechanism of the reaction was proposed. Published by Elsevier Ltd.

A mild, practical procedure for oxidative dehydrogenation with catalytic amounts of a Cu salt, K2CO3, and tert-butylhydroperoxide (TBHP) as a terminal oxidant has been developed. This oxidation procedure is generally applicable to dihydropyrimidinones and most dihydropyrimidines.

Ring closing metathesis (RCM) has emerged as a powerful tool to construct macrocyclic ring systems. However, the product distribution of monomer and oligomers is often a problem in the formation of medium to large rings. In the course of synthetic studies on the natural product radicicol and its analogs, we have found that the reaction temperature, along with concentration, has significant impact on the outcome of the product ratio. Specifically, carrying out the RCM reaction in refluxing toluene (110degreesC) at higher dilution affords improved yields of the monomeric macrocycle. Similar observations for another family of macrolactone natural products, the epothilones, are also reported. (C) 2003 Elsevier Science Ltd. All rights reserved.

The total synthesis of racemic rishirilide B has been accomplished. The synthesis serves to define the relative relationships of its stereogenic centers. Also, starting with readily available chiral pool, ent-rishirilide B was synthesized, thereby demonstrating that natural configuration of rishirilide B. The defining step in our total synthesis is the facile cycloreversion of the bis(siloxy)-benzocyclobutane and the intermolecular o-quinodimethide Diels-Alder cycloaddition. We believe that the tight regiochemical guidance in this step arises from a meshing of the electron-donating effects of the symmetry-perturbing aromatic OTBS group of the o-quinodimethide diene with the reactivity differential of the dienophile (enedione), modulated by the hydroxyl group at the alpha-position. The validity of the hypothesis of hydroxy-directed activation of its vicinal ketone function in the context of the enedione dienophile warrants further study. This type of activation may find broader applications in distinguishing reactivity profiles of key closely related functional groups in organic substrates.

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Reactions of steroidal alpha,beta-epoxy vinyl triflates in Pd-catalyzed reactions are described. Oxidative insertion of Pd-0 into the C-O bond, giving vinylpalladium 12, is faster than formation of the pi-allyl derivative from the vinyl epoxide. Although 12 can be trapped under certain conditions, it eventually rearranges to palladium alkoxide 14, which is in equilibrium with 15 and/or 10.