2,4,4,6-tetrabromo-2,5-cyclohexadien-1-one; triphenylphosphine in dichloromethane T=20°C;

hydrogen bromide T=110 - 130°C;

1.1: Mg / tetrahydrofuran 1.2: 40 percent / Li2CuCl4 / tetrahydrofuran 2.1: 90 percent / Ph3P; 2,4,4,6-tetrabromocyclohexa-2,5-dienone / CH2Cl2 / 20 °C View Scheme

1.1: POCl3 / tetrahydrofuran 2.1: Mg / tetrahydrofuran 2.2: 40 percent / Li2CuCl4 / tetrahydrofuran 3.1: 90 percent / Ph3P; 2,4,4,6-tetrabromocyclohexa-2,5-dienone / CH2Cl2 / 20 °C View Scheme

2: 1.) 82percent hydrazine hydrate, 2.) KOH / 1.) diethylene glycol, reflux, 2.) 14 h, reflux 3: 78 percent / conc. H2SO4 / 12 h / Heating 4: 1.) lithium alanate, 2.) aq.H2SO4 / 1.) THF, 2 h, reflux, 2.) methanol 5: 82 percent / HBr / 110 - 130 °C View Scheme

1: 1.) lithium alanate, 2.) aq.H2SO4 / 1.) THF, 2 h, reflux, 2.) methanol 2: 82 percent / HBr / 110 - 130 °C View Scheme

1: 1.) 82percent hydrazine hydrate, 2.) KOH / 1.) diethylene glycol, reflux, 2.) 14 h, reflux 2: 78 percent / conc. H2SO4 / 12 h / Heating 3: 1.) lithium alanate, 2.) aq.H2SO4 / 1.) THF, 2 h, reflux, 2.) methanol 4: 82 percent / HBr / 110 - 130 °C View Scheme