silica gel in 1,3,5-trimethyl-benzene 5 h; Heating;

1: 65 percent / benzene / 1) 24 h room temperature 2) 2 h boiling 2: 61 percent / activated silica gel / 1,3,5-trimethyl-benzene / 5 h / Heating View Scheme

Yield given. Multistep reaction. Yields of byproduct given;