4 A molecular sieve; H+ ion-exchange resin (Amberlyst 15) in acetonitrile T=25°C; 4 h;

With  2,2'-azo-bisisobutyronitrile; tri-n-butyl-tin hydride; sodium iodide in  diethylene glycol dimethyl ether 1.5 h;  Heating;   

Multi-step reaction with 4 steps 1: 80.5 percent / p-toluenesulfonic acid / methanol / 3 h / 25 °C2: 73 percent / pyridine / 0 °C3: 95 percent / p-toluenesulfonic acid / CH2Cl2 / 1 h / 25 °C4: 78 percent / NaI, azoisobutyronitrile, Bu3SnH / bis-(2-methoxy-ethyl) ether / 1.5 h / Heating