1: benzyl alcohol With sodium azide; tetra-(n-butyl)ammonium iodide; triethylamine; 1-(toluene-p-sulphonyl)imidazole in N,N-dimethyl-formamide T=80°C; 10 h; 2: ethyl acetoacetate With potassium hydroxide in dimethyl sulfoxide; N,N-dimethyl-formamide T=20 - 80°C; 12 h;

sodium hydride; Methanesulfonyl azide in acetonitrile 24 h; Ambient temperature;

potassium carbonate in dimethyl sulfoxide 44 h;

[Cu8(μ4-H){S2P(OEt)2}6](PF6) in N,N-dimethyl-formamide T=120°C; Huisgen Cycloaddition; 12 h; Inert atmosphere; Overall yield = 99 percent; regioselective reaction;

acetic acid T=90 - 100°C;

sodium hydroxide 2 h; Heating;

1: aq. NaOH / 2 h / Heating 2: SOCl2 / 3 h / Heating View Scheme