Leo A. Paquette

Bio: Leo A. Paquette is an academic researcher from Ohio State University. The author has contributed to research in topics: Ring (chemistry) & Total synthesis. The author has an hindex of 36, co-authored 484 publications receiving 6021 citations. Previous affiliations of Leo A. Paquette include Heidelberg University.

Dodecahedrane: improved synthetic access to, and monofunctionalization of, the spherical hydrocarbon. Spectral properties of the derivatives

Abstract: Initially described are several improvements in the synthesis of dodecahedrane precursors and dodecahedrane (XIII) itself.

Stereocontrolled Preparation of Spirocyclic Ethers by Intramolecular Trapping of Oxonium Ions with Allylsilanes.

Abstract: The stereoselectivity of the spontaneous intramolecular cyclization of 2-(benzenesulfonyl)-2-(4-((trimethylsilyl)methyl)-4-pentenyl)tetrahydropyrans substituted by alkyl groups at various ring positions has been examined. For the 4- and 6-methyl derivatives, formation of the spirocyclic center occurs exclusively anti to the methyl. The outcome in the 5-methyl example is a 3.7:1 syn/anti split. For the trans-4,6-dimethyl derivative, the substituents act in a reinforcing manner and direct cyclization uniquely in one direction. Both the cis and trans bicyclic ethers ring close on that π-surface of the intermediate oxonium ion syn to the angular hydrogen. The results are rationalized in terms of the predilection of the associated oxonium ions for nucleophilic capture via a chairlike or twist-boat transition state.

Direct Synthesis of Previously Inaccessible Bridgehead Azabicyclics by Intramolecular Cyclization of α-Sulfonamido and α-Sulfonimido Radicals

Abstract: Syntheses of the first bridgehead sultams and the only known bridgehead disulfonimide are described. Both approaches capitalize on the electrophilicity of α-sulfonyl radicals and their propensity to undergo intramolecular ring closure. Where double bonds are concerned, 5-exo and 6-exo pathways operate preferentially as long as structural strain is not excessive. When the reaction center is a carbon−carbon triple bond, the first cyclization gives rise to vinyl radicals that hold sufficient reactivity to capture solvent benzene. In the case of 45, this sequential reaction leads importantly to the introduction of a styrene functionality sufficiently activated to allow a second ring closure to be kinetically feasible. The solid-state structural features of 12 and 17 have been elucidated by X-ray crystallographic methods. Despite key differences from the norm in the alignment of the nitrogen lone pair relative to the adjacent sulfonyl groups, these compounds exhibit good hydrolytic stability. For 13, generatio...

C4'-spiroalkylated nucleosides having sulfur incorporated at the apex position.

Abstract: Methodology based on the concept of thionium ion-initiated pinacolic ring expansion has been developed for accessing C4'-spirocyclic thionucleosides. The readily available racemic ketones 6 and 37 are conveniently resolved via their acetals with (R)-mandelic acid. Subsequent reactions beginning with utilization of the Pummerer rearrangement lend themselves to functionalization of the spirocyclic core and ultimately incorporation of the nucleosidic bases. Limitations to this strategy are pointed out. Acquisition of the alpha- and beta-isomers at C4' is equally facile. Absolute configurational assignments have been made possible by X-ray crystallography.

C-H bond functionalization: emerging synthetic tools for natural products and pharmaceuticals

Abstract: The direct functionalization of C-H bonds in organic compounds has recently emerged as a powerful and ideal method for the formation of carbon-carbon and carbon-heteroatom bonds. This Review provides an overview of C-H bond functionalization strategies for the rapid synthesis of biologically active compounds such as natural products and pharmaceutical targets.

Palladium-catalyzed cross-coupling reactions in total synthesis.

Abstract: In studying the evolution of organic chemistry and grasping its essence, one comes quickly to the conclusion that no other type of reaction plays as large a role in shaping this domain of science than carbon-carbon bond-forming reactions. The Grignard, Diels-Alder, and Wittig reactions are but three prominent examples of such processes, and are among those which have undeniably exercised decisive roles in the last century in the emergence of chemical synthesis as we know it today. In the last quarter of the 20th century, a new family of carbon-carbon bond-forming reactions based on transition-metal catalysts evolved as powerful tools in synthesis. Among them, the palladium-catalyzed cross-coupling reactions are the most prominent. In this Review, highlights of a number of selected syntheses are discussed. The examples chosen demonstrate the enormous power of these processes in the art of total synthesis and underscore their future potential in chemical synthesis.

Organic Reactions in Aqueous Media with a Focus on Carbon−Carbon Bond Formations: A Decade Update

Abstract: 4.2.8. Reductive Coupling 3109 5. Reaction of Aromatic Compounds 3110 5.1. Electrophilic Substitutions 3110 5.2. Radical Substitution 3111 5.3. Oxidative Coupling 3111 5.4. Photochemical Reactions 3111 6. Reaction of Carbonyl Compounds 3111 6.1. Nucleophilic Additions 3111 6.1.1. Allylation 3111 6.1.2. Propargylation 3120 6.1.3. Benzylation 3121 6.1.4. Arylation/Vinylation 3121 6.1.5. Alkynylation 3121 6.1.6. Alkylation 3121 6.1.7. Reformatsky-Type Reaction 3122 6.1.8. Direct Aldol Reaction 3122 6.1.9. Mukaiyama Aldol Reaction 3124 6.1.10. Hydrogen Cyanide Addition 3125 6.2. Pinacol Coupling 3126 6.3. Wittig Reactions 3126 7. Reaction of R,â-Unsaturated Carbonyl Compounds 3127

Cascade reactions in total synthesis.

Abstract: The design and implementation of cascade reactions is a challenging facet of organic chemistry, yet one that can impart striking novelty, elegance, and efficiency to synthetic strategies. The application of cascade reactions to natural products synthesis represents a particularly demanding task, but the results can be both stunning and instructive. This Review highlights selected examples of cascade reactions in total synthesis, with particular emphasis on recent applications therein. The examples discussed herein illustrate the power of these processes in the construction of complex molecules and underscore their future potential in chemical synthesis.