Synthesis of Substituted Oligothiophenes and X‐Ray Crystal Structures of 3′‐Methyl‐2,2′:5′,2′′‐terthiophene, 3,3′′‐Dimethyl‐2,2′:5′,2′′‐ terthiophene, and 5′‐(2‐Thienyl)‐2,2′:3′,2′′‐terthiophene.