The synthesis of 1,2,3-trisubstituted cyclopenta[b]thiophenes was achieved through a Brønsted acid mediated domino process under solvent-free conditions. In this one-pot process, benzothienylation of 1,3-dicarbonyls follows an intramolecular aldol-type reaction leading to the generation of functionalized and highly substituted annulated benzothiophenes. This class of compounds find potential applications in molecular electronics and exhibit significant biological activities. A brief theoretical investigation established a significant relationship between the energy of the regioisomers and their distribution. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.