This paper describes a convenient preparation of tetrathia--helicene (TH), the generation of the α-anion on the terminal thiophene ring, and the synthesis of the 2-formyl-tetrathia--helicene (2-CHO-TH). The key intermediate trans-1,2-dibenzodithiophene-ethene, prepared in 97% yield by McMurry coupling of the 2-formyl-benzo[1,2-b;4,3-b′]dithiophene, was transformed into TH using a known procedure. The described method affords TH in 46% overall yield, which is more than four times the yield previously reported in the literature. The α-anion of TH, which is easily generated on the α-position of one of the terminal thiophene rings, reacts with electrophilic reagents such as D2O and DMF. The latter reaction proved to be the best way to prepare 2-CHO-TH, a key intermediate for the preparation of new substituted heterohelicenes.
|Titolo:||A convenient procedure for the synthesis of tetrathia--helicene and the selective α-functionalization of its terminal thiophene ring|
MAIORANA, STEFANO (Primo)
|Parole Chiave:||Heterohelicenes; Large-scale preparation; McMurry reaction; NLO properties; Oxidative photocyclisation|
|Settore Scientifico Disciplinare:||Settore CHIM/06 - Chimica Organica|
|Data di pubblicazione:||2003|
|Digital Object Identifier (DOI):||10.1016/S0040-4020(03)01056-1|
|Appare nelle tipologie:||01 - Articolo su periodico|