Organolithium reagents are used in both academic and industrial laboratories to carry out complex syntheses of medicinally important compounds. The underlying solvent- dependent aggregates and mechanisms of reaction are as complex as in any sub discipline in organometallic chemistry. We are the only group in the world with expertise in synthetic organic, organometallic, physical organic, analytical, and computational chemistry together in a single laboratory to produce fully integrated studies of structure, mechanism, and selectivity. In this proposal, we continue studies of the chemistry of lithium dialkylamides used prominently as the base of choice for difficult metalations central to many C-C bond forming processes. The program is fully integrated starting from a synthetic goal, observation, or question. Through a combination of structural and mechanistic studies we answer key questions or offer solutions to key problems. In this proposal we will focus on several pressing topics including: (1) We will complete studies of lithium diisopropylamide (LDA)-mediated metalations that all occur under the synthetically prominent conditions (THF at -78 oC) in which, ironically, complexity reaches a zenith because the aggregate-aggregate exchanges are not at equilibrium. (2) Related studies will focus on poorly understood LDA-LiX mixed aggregation effects observed under equilibrium conditions. (3) A collaboration starting with Amgen and expanding to include Zakarian (UCSB) will explore the structural and mechanistic basis of highly enantioselective reactions using a chiral dilithiated tetraamine. (4) Asymmetric C-N bond formation via 1,4-additions will be examined from a number of angles, all founded on previous studies in our lab. (5) The most overlooked of the three most prominent lithium amides-lithium tetramethylpiperdide-will be studied with the goal of expanding our understanding of how it metalates as well as developing pharmaceutically important hydrocarbon-soluble analogs. (6) Studies in collaboration with Paul Knochel of the rapidly developing class of tetramethylpiperidides based on magnesium and zinc will be examined. Overall, the work described in 6 aims promises to expand our most basic understanding of lithium amide structure-reactivity relationships and develop methods for use in organic synthesis.

Public Health Relevance

Lithium amides are reactive intermediates used by both academic and pharmaceutical process chemistry laboratories on a daily basis around the globe. Some are the most commonly used reagents in organic synthesis. Our structural and mechanistic studies are designed to understand and improve their efficacy and have led to advances through collaborations with major pharmaceutical companies.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Synthetic and Biological Chemistry A Study Section (SBCA)
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Lees, Robert G
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Cornell University
Schools of Arts and Sciences
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Mack, Kyle A; Collum, David B (2018) Case for Lithium Tetramethylpiperidide-Mediated Ortholithiations: Reactivity and Mechanisms. J Am Chem Soc 140:4877-4883
Li, Beryl X; Le, Diane N; Mack, Kyle A et al. (2017) Highly Stereoselective Synthesis of Tetrasubstituted Acyclic All-Carbon Olefins via Enol Tosylation and Suzuki-Miyaura Coupling. J Am Chem Soc 139:10777-10783
Yu, Kai; Lu, Ping; Jackson, Jeffrey J et al. (2017) Lithium Enolates in the Enantioselective Construction of Tetrasubstituted Carbon Centers with Chiral Lithium Amides as Noncovalent Stereodirecting Auxiliaries. J Am Chem Soc 139:527-533
Algera, Russell F; Gupta, Lekha; Hoepker, Alexander C et al. (2017) Lithium Diisopropylamide: Nonequilibrium Kinetics and Lessons Learned about Rate Limitation. J Org Chem 82:4513-4532
Algera, Russell F; Ma, Yun; Collum, David B (2017) Sodium Diisopropylamide in Tetrahydrofuran: Selectivities, Rates, and Mechanisms of Alkene Isomerizations and Diene Metalations. J Am Chem Soc 139:11544-11549
Algera, Russell F; Ma, Yun; Collum, David B (2017) Sodium Diisopropylamide in Tetrahydrofuran: Selectivities, Rates, and Mechanisms of Arene Metalations. J Am Chem Soc 139:15197-15204
Reyes-Rodríguez, Gabriel J; Algera, Russell F; Collum, David B (2017) Lithium Hexamethyldisilazide-Mediated Enolization of Acylated Oxazolidinones: Solvent, Cosolvent, and Isotope Effects on Competing Monomer- and Dimer-Based Pathways. J Am Chem Soc 139:1233-1244
Algera, Russell F; Ma, Yun; Collum, David B (2017) Sodium Diisopropylamide: Aggregation, Solvation, and Stability. J Am Chem Soc 139:7921-7930
Mack, Kyle A; McClory, Andrew; Zhang, Haiming et al. (2017) Lithium Hexamethyldisilazide-Mediated Enolization of Highly Substituted Aryl Ketones: Structural and Mechanistic Basis of the E/Z Selectivities. J Am Chem Soc 139:12182-12189
Ma, Yun; Algera, Russell F; Collum, David B (2016) Sodium Diisopropylamide in N,N-Dimethylethylamine: Reactivity, Selectivity, and Synthetic Utility. J Org Chem 81:11312-11315

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