Methods of stabilizing thiophene derivatives of the general formula (I) by treatment with basic compounds: wherein R1 and R2 each independently represents a moiety selected from the group consisting of hydrogen, optionally substituted C1-20 alkyl groups which can contain up to 5 heteroatoms selected from the group consisting of oxygen and sulfur, optionally substituted C1-20 oxyalkyl groups which can contain up to 5 heteroatoms selected from the group consisting of oxygen and sulfur, or wherein R1 and R2 together represent a fused cyclic moiety selected from the group consisting of optionally substituted C1-20 dioxyalkylene groups and C1-20 dioxyarylene groups; and stabilized thiophene derivatives that can be prepared by such methods.