Synthesis and characterization of 4-(dimethylaminopyridyl)chalcogenides (Se, Te): X-ray structure of bis(4-dimethylamino-2-pyridyl) diselenide, bis(4-dimethylamino-2-pyridylselenenyl)methane and 4-dimethylamino-2,6-bis(methylselenenyl)pyridine

The utility of BF3-aided lithiation of 4-dimethylaminopyridine (1) with lithium diisopropylamide (LDA) or lithium tetramethylpiperidide (LTMP) in the synthesis of 4-(dimethylaminopyridyl)chalcogenides (Se, Te) has been studied. The lithiation of the in situ generated 4-dimethylaminopyridine-BF3 adduct (2) with LTMP (1.1 eq.) followed by chalcogen insertion and electrophilic quenching reaction afforded the corresponding pyridylchalcogenides in excellent yields. The use of LDA with a modified procedure gave pyridylchalcogenides in yields comparable to that obtained with LTMP. Single crystal X-ray studies of bis(4-dimethylamino-2-pyridyl) diselenide (6), bis(4-dimethylamino-2-pyridylselenenyl)methane (9) and 4-dimethylamino-2,6-bis(methylselenenyl)pyridine (11) have also been reported. The structural analysis reveals a rare cis, trans conformation among the bis(2-pyridyl) diselenides in 6 and π⋯π stacking interactions between the pyridine rings in 9.