Fig. 5: Application explorations. | Nature Communications

Fig. 5: Application explorations.

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

Fig. 5

a Product elaboration: Reaction conditions: (a) Ph3PAuCl (20 mol%), MeOH, 50 °C, 8 h; (b) 4-fluorophenyl isocyanate (1.0 equiv), Et2O, 4 h, then NaOMe (2.0 equiv), MeOH, 50 °C, 2 h, Ar = 4-FC6H4; (c) 4-fluorophenyl isocyanate (1.0 equiv), Et2O, 4 h, then Ph3PAuCl (5.0 mol%), MeOH, 50 °C, 24 h, Ar = 4-FC6H4; (d) zidovudine (1.0 equiv), CuSO4 ∙ 5H2O (10 mol%), sodium ascorbate (20 mol%), tBuOH/H2O (1:1, v/v), rt, 4 h; (e) Pd/C (10 mol% Pd), H2 (1.0 atm), MeOH (1.0 mL), 50 °C, 6 h; (f) Lindlar catalyst (10 mol% Pd), quinoline (2.0 equiv), H2 (1.0 atm), EtOAc, rt, 10 min; (g) Pd(PPh3)4 (10 mol%), CuI (10 mol%), PhI (1.5 equiv), Et3N (10 equiv), DMF, 55 °C, 3 h. Isolated yield. The e.e. values were determined by chiral HPLC analysis. b Tandem reaction: The propargylic hydrazination/carboxylative cyclization sequence. For hydrazination step: according to standard condition; For carboxylative cyclization step: AgOTs (50 mol%), 1,3-diphenylguanidine (1.2 equiv), CO2 (3.0 MPa) at 25 oC for 72 h. Isolated yield. The e.e. values were determined by chiral HPLC analysis.

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