Thieno-pyridines lithiation

Electrophilic cyclization of the precursors 8, which are available from 3-(methylthio)pyridine by regioselective lithiation, followed by introduction of CBr4, and a subsequent Sonogashira coupling, has resulted in a series of thieno[3,2-b]pyridines 9... 

There are several bicyclic compounds with five-membered heterocycles fused to pyridine rings, where metalation occurs in the smaller ring due to activation by the heteroatom. The ring-A lithiation of imidazopyridines and pyrimidines was discussed in Section II,E,6, but in addition, the a-lithio derivatives of thieno[2,3-6]pyridine 119 (74JHC355), thieno[3,2-... 

Lithiation of compounds 8.110 generally takes place at the 2-position [as, e.g., in thieno[3,2-b]pyridine (84JHC785), furo[3,2-c]pyridine (83T1777), and thieno[2,3-b]pyridine (74JHC355)]. However, in thie-no[2,3-6]pyrazine lithiation occurs at the 5- and 6-positions in a 17 83 ratio (80JHC1019). Compounds of type 8.111 undergo lithiation as follows imidazo[l,2-[Pg.236]

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