Frank E. McDonald

Bio: Frank E. McDonald is an academic researcher from Emory University. The author has contributed to research in topics: Cycloisomerization & Alkyne. The author has an hindex of 41, co-authored 143 publications receiving 4363 citations. Previous affiliations of Frank E. McDonald include Northwest University (United States) & Yale University.

Organolanthanide-Catalyzed Hydroamination/Cyclization. Efficient Allene-Based Transformations for the Syntheses of Naturally Occurring Alkaloids

Abstract: The total syntheses of the pyrrolidine alkaloid (+)-197B (1) and pyrrolizidine alkaloid (+)-xenovenine (2) are described. The strategy involves enantioselective syntheses of the aminoallene, (5S,8S)-5-amino-trideca-8,9-diene (3), and the aminoallene-alkene, (5S)-5-amino-pentadeca-1,8,9-triene (4), which then undergo regio- and stereoselective cyclohydroamination catalyzed by the organolanthanide precatalysts Cp‘2LnCH(TMS)2 and Me2SiCp‘ ‘(tBuN)LnN(TMS)2 (Cp‘ = η5-Me5C5; Cp‘ ‘ = η5-Me4C5; Ln = lanthanide; TMS = Me3Si). These reactive organolanthanide complexes efficiently mediate highly diastereoselective intramolecular hydroamination/cyclization (IHC) reactions under mild conditions. The turnover-limiting step in these catalytic cycles is proposed to be intramolecular insertion into the Ln−N bond of the proximal allenic CC linkage, followed by rapid protonolytic cleavage of the resulting Ln−C bond. The rate and selectivity of the insertion process is highly sensitive to the steric demands of the substrate.

Stereoselective Glycosylations of a Family of 6-Deoxy-1,2-glycals Generated by Catalytic Alkynol Cycloisomerization

Abstract: Photolysis of 0.25 equiv of W(CO)6 in the presence of tertiary amines (triethylamine or DABCO) and highly functionalized terminal alkynyl alcohols catalyzes single-step, high-yield cycloisomerization to endocyclic enol ethers. This transformation is general for each diastereomeric 3,4-bissilyl ether of 5-hydroxy-1-hexyne, leading to enantio- and diastereoselective syntheses of each isomer of 6-deoxy-1,2-glycals. Stereoselective glycosylations have also been demonstrated for each glycal diastereomer, and have been applied in the preparation of d-digitoxose-β-4-d-digitoxose glycal.

Alkynol endo-Cycloisomerizations and Conceptually Related Transformations

Abstract: The discovery of new chemical transformations permits exploration and development of novel synthesis strategies. This account describes the invention of endo-selective cycloisomerizations of alkynyl alcohols, and mechanistically related transformations of terminal alkynes tethered to nitrogen, carbon, and sulfur nucleophiles (see diagram). The synthetic utility of these new transformations is exemplified in applications to anti-AIDS nucleosides, polycyclic ethers, and oligosaccharides.

Catalytic Carbophilic Activation: Catalysis by Platinum and Gold π Acids

Abstract: The ability of platinum and gold catalysts to effect powerful atom-economic transformations has led to a marked increase in their utilization. The quite remarkable correlation of their catalytic behavior with the available structural data, coordination chemistry, and organometallic reactivity patterns, including relativistic effects, allows the underlying principles of catalytic carbophilic activation by π acids to be formulated. The spectrum of reactivity extends beyond their utility as catalytic and benign alternatives to conventional stoichiometric π acids. The resulting reactivity profile allows this entire field of catalysis to be rationalized, and brings together the apparently disparate electrophilic metal carbene and nonclassical carbocation explanations. The advances in coupling, cycloisomerization, and structural reorganization—from the design of new transformations to the improvement to known reactions—are highlighted in this Review. The application of platinum- and gold-catalyzed transformations in natural product synthesis is also discussed.

Hydroamination: direct addition of amines to alkenes and alkynes.

Abstract: 8.4.5. Nitromercuration Reactions 3878 9. Hydroamination of Alkenes and Alkynes under Microwave Irradiation 3878 * To whom correspondence should be addressed. Phone: +49 241 8