Fig. 2: Reaction development. | Nature Communications

Fig. 2: Reaction development.

From: Trifluoroethanol-assisted asymmetric propargylic hydrazination to α-tertiary ethynylhydrazines enabled by sterically confined pyridinebisoxazolines

Fig. 2

a Influences of hydrazine derivatives. b Effects of the ligands. c Effects of the solvent. Reagents and conditions: 1a (0.10 mmol), 2 (0.12 mmol), CuCl2 ·  2H2O (10 mol%), PYBOX ligand (12 mol%), DIPEA (1.0 equiv), solvent (1.0 mL), 0 °C, 48 h. NMR yield with 1,3,5-trimethoxybenzene as internal standard. The e.e. was determined by chiral HPLC analysis. d Left:13C NMR analysis for the interaction of TFE or EtOH with 2a. Right: 19F NMR study on the interaction of TFE with 2a. e DFT calculations to examine the influence of the fluoro-atom on the interaction of alcohol with 2a. The bond distances are given in angstroms and the natural bond oribital (NBO) charges are in parentheses. aDetected by GC analysis. bDIPEA (2.0 equiv). cCuCl2 · 2H2O (2.0 mol%), DABCO (1.0 equiv) in TFE at –20 °C. dIsolated yield. RSM: recovery of starting material. DIPEA diisopropylethylamine, TFE trifluoroethanol, BP byproduct, HFIP hexafluoroisopropanol.

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