For the screening novel ionic liquids (ILs), it’s important to predict the crystal structure of solid-state ILs so that the melting-point of the ILs can be calculated using already developed methods. We introduce a method combining genetic-algorithm-based structure evolution and forcefield-base molecular dynamics to predict the most energetically stable structure of an IL. Our example showed the structure evolution can be successfully, and the time cost of this method is quite short compared with DFT approach. We believe that this is a feasible method to predict the crystal structure of novel ILs which can facilitate the prediction of their melting-points.Continue reading
We employ Markov States models (MSMs) and transition path theory to elucidate the ensemble kinetic pathways of heterogeneous ice nucleation (HIN) simulated by Molecular dynamics simulations. Interestingly, our MSM reveals the coexistence of classical and non-classical nucleation pathways with comparable fluxes at T=230K. Specifically, the classical HIN pathway shown by purple arrows, follows a typical one-step ice nucleation process, corresponding to a direct transition from liquid to hexagonal ice (green spheres). While the non-classical nucleation shown in red and orange arrows proceeds via two-step pathways with square ice (violet spheres) formed as an intermediate state.Continue reading
Described here is a highly efficient synthesis of hydrodibenzofurans, an important structural unit lacking general access, in particular, with contiguous quaternary stereocenters. In the presence of HNTf2 as the superior catalyst and mCPBA as an oxidant, the readily available styrene substrates underwent a one-pot cascade process comprising epoxidation, semipinacol rearrangement, and hemiketal formation to furnish hydrodibenzofurans with good efficiency and diastereoselectivity.Continue reading
Herein we disclose a new catalytic asymmetric approach for the synthesis of chiral α-amino ketones, which is particularly useful for the less accessible acyclic α-tertiary cases. By a protonation-amination sequence, our approach represents a rare asymmetric H−heteroatom bond insertion by α-carbonyl sulfonium ylides, an attractive surrogate of diazocarbonyls. The mild intermolecular C–N bond formation was catalyzed by chiral phosphoric acids with excellent efficiency and enantioselectivity. The products are precursors to other important chiral amine derivatives, including drug molecules and chiral ligands. The enantioselectivity was controlled by dynamic kinetic resolution in the amination step, rather than the initial protonation.Continue reading
We herein present the design and synthesis of a structurally unique oxa-spirocyclic bisphosphine ligand, termed as O-SDP. The bisphosphine ligand O-SDP derived from O-SPINOL has a relatively larger bite angle compared with that of SDP, and O-SDP has been successfully applied in the ruthenium-catalyzed asymmetric hydrogenation of tetra-substituted and tri-substituted α,β-unsaturated carboxylic acids under base-free conditions.
The synthetic utility of the protocol is highlighted by its synthetic application in key intermediates for chiral drugs.
Wogonin is a natural flavonoid isolated in a plant known as Scutellaria baicalensis or Skullcap. Studies found wogonin has anti-cancer property but very few reported about its structural chemistry. This study will explore the crystal structure of anhydrous wogonin via desolvation. The ethyl acetate solvate crystals (left) was heated under mild condition which afforded a new stable anhydrous form of wogonin (right), with a triclinic P-1 crystal. PXRD and thermogravimetric analyses validated the results.Continue reading
A preliminary batch of 15 substituted variations of the cocrystal2-4 between 11-azaartemisinin and salicylic acid (11-Aza: SalA) using substituted SalA compounds were prepared. In all cases to-date a molecular pair with retained synthon is present, these form 2-fold screw stacks with similar geometry.Continue reading
Resolution of racemic 1-phenylethylamine is quite challenging since there is a single chiral centre with strong shape similarity between enantiomers of the racemic pair. Optimal resolution was found for 4-ClPh anion which affords R-[NH3CHMePh] cation, in which salt the chiral pocket for the cation has a different shape and surface functionality compared to the parent. This leads to a higher %ee since solid solution incorporation of the enantiomer is suppressed. The hand of the enantiopure amine can be switched to the S-cation by changing the solvent or the use of D-tartramide anions.Continue reading