Liam A. McLean

Bio: Liam A. McLean is an academic researcher from University of St Andrews. The author has contributed to research in topics: Protonation & Enantioselective synthesis. The author has co-authored 2 publications.

Asymmetric synthesis of heterocyclic chloroamines and aziridines by enantioselective protonation of catalytically generated enamines

Abstract: We report a method for the synthesis of chiral vicinal chlo-roamines via asymmetric protonation of catalytically gener-ated prochiral chloroenamines using chiral Bronsted acids. The process is highly enantioselective, with the origin of asymmetry and catalyst substituent effects elucidated by DFT calculations. We show the utility of the method as an approach to the synthesis of a broad range of heterocycle-substituted aziridines by treatment of the chloroamines with base in a one-pot process, as well as the utility of the process to allow access to vicinal diamines.

London Dispersion Effects in a Distannene/Tristannane Equilibrium: Energies of their Interconversion and the Suppression of the Monomeric Stannylene Intermediate.

Abstract: Reaction of {LiC6H2-2,4,6-Cyp3·Et2O}2 (Cyp = cyclopentyl) (1) of the new dispersion energy donor (DED) ligand, 2,4,6-triscyclopentylphenyl with SnCl2 afforded a mixture of the distannene {Sn(C6H2-2,4,6-Cyp3)2}2 (2), and the cyclotristannane {Sn(C6H2-2,4,6-Cyp3)2}3 (3). 2 is favored in solution at higher temperature (345 K or above) whereas 3 is preferred near 298 K. Van't Hoff analysis revealed the 3 to 2 conversion has a ΔH = 33.36 kcal mol-1 and ΔS = 0.102 kcal mol-1 K-1, which gives a ΔG300 K = +2.86 kcal mol-1, showing that the conversion of 3 to 2 is an endergonic process. Computational studies show that DED stabilization in 3 is -28.5 kcal mol-1 per {Sn(C6H2-2,4,6-Cyp3)2 unit, which exceeds the DED energy in 2 of -16.3 kcal mol-1 per unit. The data clearly show that dispersion interactions are the main arbiter of the 3 to 2 equilibrium. Both 2 and 3 possess large dispersion stabilization energies which suppress monomer dissociation (supported by EDA results).

London Dispersion Effects in a Distannene/Tristannane Equilibrium: Energies of their Interconversion and the Suppression of the Monomeric Stannylene Intermediate

Abstract: Reaction of {LiC6H2−2,4,6-Cyp3⋅Et2O}2 (Cyp=cyclopentyl) (1) of the new dispersion energy donor (DED) ligand, 2,4,6-triscyclopentylphenyl with SnCl2 afforded a mixture of the distannene {Sn(C6H2−2,4,6-Cyp3)2}2 (2), and the cyclotristannane {Sn(C6H2−2,4,6-Cyp3)2}3 (3). 2 is favored in solution at higher temperature (345 K or above) whereas 3 is preferred near 298 K. Van't Hoff analysis revealed the 3 to 2 conversion has a ΔH=33.36 kcal mol−1 and ΔS=0.102 kcal mol−1 K−1, which gives a ΔG300 K=+2.86 kcal mol−1, showing that the conversion of 3 to 2 is an endergonic process. Computational studies show that DED stabilization in 3 is −28.5 kcal mol−1 per {Sn(C6H2−2,4,6-Cyp3)2 unit, which exceeds the DED energy in 2 of −16.3 kcal mol−1 per unit. The data clearly show that dispersion interactions are the main arbiter of the 3 to 2 equilibrium. Both 2 and 3 possess large dispersion stabilization energies which suppress monomer dissociation (supported by EDA results).