Process for the preparation of benzodithiophene compounds

A process for the preparation of a benzodithiophene compound having general formula (I):

• wherein:
• R1 and R2 are each independently selected from a hydrogen atom, a linear or branched C1-C20 alkyl group, a cycloalkyl group and an aryl group, said groups being optionally substituted;
• R3 is selected from:
• a hydrogen atom H, —CHO or —CN;
• a group selected from R, —OR, —COR, —COOR and R—O—[CH2—CH2—O]n— wherein R is a linear or branched C1-C20 alkyl group, a cycloalkyl group optionally substituted or an aryl group optionally substituted, and n is an integer ranging from 1 to 4;
• a —R′OR4 group wherein R′ represents a linear or branched C1-C20 alkylene group and R4 is selected from H, a linear or branched C1-C20 alkyl group, and a polyethyleneoxyl group R5—[—OCH2—CH2—]n— wherein R5 is a C1-C20 alkyl group and n is an integer ranging from 1 to 4;
• X is selected from a nitrogen atom and a CR6 group, wherein R6 is selected from a hydrogen atom, a linear or branched C1-C20 alkyl group, a cycloalkyl group optionally substituted, an aryl group optionally substituted, a heteroaryl group optionally substituted, a —CHO group, a —CN group, a Y group selected from —COR, a —COOR group, and a —CONR2 group, wherein R is selected from a linear or branched C1-C20 alkyl group, a cycloalkyl group optionally substituted and an aryl group optionally substituted,
• wherein said process comprises reacting a derivative of 3,3′-bithiophene having general formula (II):
• wherein X and R3 have the same meanings described above, with at least one internal alkyne having general formula (III)
• wherein R1 and R2 have the meanings described above.