Syntheses of Novel Group 15 and 16 Thieno[2,3-b]-, Thieno[3,4-b]-, and Thieno[3,2-b]-heteroles

Group 15 (P, As and Sb) and group 16 (S, Se, andTe) thieno[2,3-b]-(1).thieno[3,4-61-(2).and thieno[3,2-b]heteroles (3) were prepared from the corresponding 1,4-dilithium intermediates, derived from (a-(a-bromo-Btrimethylsilylvinyl)thiophenes (6), (1 O), and (1 3) by treatment with fertbutyllithium, respectively.These thienoheteroles obtained are novel fused heterocyclic ring systems, except for thienothophenes and thienoselenophenes.Although a variety of new five-five fused aromatic heterccyclicring systems containing one heteroatom in each ring have been prepared, most of these systems so far reported consist of the well-known simple heteroles such as furan, pyrrole, and thiophene rings.'With regard to thienoheteroles represented by the structures (1)-(3), t h i e n ~~~r r o l e s , ~ thienothiophenes, 3*4 and thienoselenophenes 3.5 have been prepared.However, their synthetic routes are not always versatile and thienoheteroles containing an element other than the above elements (N, S , and Se) are little known.Therefore, we are interested in the synthesis of these fused systems containing Main Group heavier elements and report here versatile synthetic routes to group 15 (P, As, Sb) and group 16 (5, Se, Te) thieno[2,3-b]-(I), thieno[3,4-61-(2), and thieno[3,2-h]heteroles (3), each of which can be obtained from a corresponding common starting material.