1: (3-dibromomethylene-penta-1,4-diynyl)-benzene With n-butyllithium in hexane; toluene T=-20 - 0°C; Fritsch-Buttenburg-Wiechell rearrangement; 2: formaldehyd in diethyl ether; hexane; toluene T=-20 - 20°C;

potassium carbonate in methanol T=23°C; 12 h;

tetrabutyl ammonium fluoride in tetrahydrofuran T=20°C;

1.1: 6.86 g / PPH3; 2,6-lutidine / CH2Cl2 / 0.5 h / 0 °C 2.1: n-BuLi / tetrahydrofuran; hexane / 0.5 h / -78 °C 2.2: ZnBr2 / tetrahydrofuran; hexane / -78 - 25 °C 2.3: 71 percent / Pd(DPEphos)Cl2 / tetrahydrofuran; hexane / 8 h / 0 °C 3.1: 81 percent / K2CO3 / methanol / 12 h / 23 °C View Scheme

1.1: n-BuLi / tetrahydrofuran; hexane / 0.5 h / -78 °C 1.2: tetrahydrofuran; hexane / -78 - 23 °C 2.1: 6.86 g / PPH3; 2,6-lutidine / CH2Cl2 / 0.5 h / 0 °C 3.1: n-BuLi / tetrahydrofuran; hexane / 0.5 h / -78 °C 3.2: ZnBr2 / tetrahydrofuran; hexane / -78 - 25 °C 3.3: 71 percent / Pd(DPEphos)Cl2 / tetrahydrofuran; hexane / 8 h / 0 °C 4.1: 81 percent / K2CO3 / methanol / 12 h / 23 °C View Scheme

1.1: n-BuLi / tetrahydrofuran; hexane / 0.5 h / -78 °C 1.2: ZnBr2 / tetrahydrofuran; hexane / -78 - 25 °C 1.3: 71 percent / Pd(DPEphos)Cl2 / tetrahydrofuran; hexane / 8 h / 0 °C 2.1: 81 percent / K2CO3 / methanol / 12 h / 23 °C View Scheme

1.1: 77 percent / potassium carbonate / tetrahydrofuran; methanol / 20 °C 2.1: BuLi / toluene; hexane / -20 - 0 °C 2.2: 72 percent / diethyl ether; toluene; hexane / -20 - 20 °C View Scheme

hydroxylamine hydrochloride; ethylamine; copper(l) chloride in tetrahydrofuran

(i) EtNH2, CuCl, NH2OH*HCl, MeOH, (ii) /BRN= 606222/; Multistep reaction;