Synthesis of Acrylonitrile from Renewable Lactic Acid.

Acrylonitrile (ACN) is widely used as monomer in the synthesis of polymers and carbon fibers. Nowadays, its production is based on fossil resources. Herein, an alternative process based on renewable resources is presented. Lactic acid (LA), which can be obtained by fermentation of biomass, was converted to ACN in two steps with an overall selectivity of 57 %. In the first step, a direct amidation of LA in the presence of water was conducted at 230 °C. Zeolites can catalyze the formation of lactamide, and a selectivity of 92 % was reached at 33 % conversion with NH4 -ZSM-5. In the second step, the dehydration of lactamide to ACN was performed with acetic anhydride, and an ACN selectivity of 62 % was achieved at full conversion.

Total synthesis of the Isodon diterpene sculponeatin†N.

The total synthesis of sculponeatin N, a bioactive polycyclic diterpene isolated from Isodon sculponeatus, is reported. Key features of the synthesis include diastereoselective Nazarov and ring-closing metathesis reactions, and a highly efficient formation of the bicyclo[3.2.1]octane ring system by a reductive radical cyclization.

Mechanism and the origins of stereospecificity in copper-catalyzed ring expansion of vinyl oxiranes: a traceless dual transition-metal-mediated process.

Density functional theory computations of the Cu-catalyzed ring expansion of vinyloxiranes is mediated by a traceless dual Cu(I)-catalyst mechanism. Overall, the reaction involves a monomeric Cu(I)-catalyst, but a single key step, the Cu migration, requires two Cu(I)-catalysts for the transformation. This dual-Cu step is found to be a true double Cu(I) transition state rather than a single Cu(I) transition state in the presence of an adventitious, spectator Cu(I). Both Cu(I) catalysts are involved in the bond forming and breaking process. The single Cu(I) transition state is not a stationary point on the potential energy surface. Interestingly, the reductive elimination is rate-determining for the major diastereomeric product, while the Cu(I) migration step is rate-determining for the minor. Thus, while the reaction requires dual Cu(I) activation to proceed, kinetically, the presence of the dual-Cu(I) step is untraceable. The diastereospecificity of this reaction is controlled by the Cu migration step. Suprafacial migration is favored over antarafacial migration due to the distorted Cu π-allyl in the latter.

Distinct biological effects of golgicide a derivatives on larval and adult mosquitoes.

A collection of Golgicide A (GCA) analogs has been synthesized and evaluated in larval and adult mosquito assays. Commercially available GCA is a mixture of four compounds. One enantiomer (GCA-2) of the major diastereomer in this mixture was shown to be responsible for the unique activity of GCA. Structure-activity studies (SAR) of the GCA architecture suggested that the pyridine ring was most easily manipulated without loss or gain in new activity. Eighteen GCA analogs were synthesized of which five displayed distinct behavior between larval and adult mosquitos, resulting in complete mortality of both Aedes aegypti and Anopheles stephensi larvae. Two analogs from the collection were shown to be distinct from the rest in displaying high selectivity and efficiency in killing An. stephensi larvae.

Synthesis of allylic and homoallylic alcohols from unsaturated cyclic ethers using a mild and selective C-O reduction approach.

Unsaturated cyclic ethers can be mildly and selectively reduced with catalytic amounts of B(C(6)F(5))(3) in the presence of an alkylsilane. The allylic position is preferentially reduced with minimal or no scrambling of olefin geometry. For electronically equivalent substrates, steric factors guide the reducing agent to the least substituted site.

Intermolecular oxonium ylide mediated synthesis of medium-sized oxacycles.

Detailed in this account are our efforts toward efficient oxacycle syntheses. Two complementary approaches are discussed, with both employing chemoselective allyl ether activation and rearrangement as the key step. Vinyl substituted oxiranes and oxetanes provide a single step access to dihydropyrans and tetrahydrooxepines. Oxiranes proved to be poor substrates, while oxetanes were slightly better. An alternative approach using substituted allyl ethers proved successful and addressed the limitations encountered in the ring expansions.