Divergent reactivities of 2-pyridyl sulfonate esters. Exceptionally mild access to alkyl bromides and 2-substituted pyridines

A series of 2- and 3-pyridyl sulfonate and tosylate esters of primary and secondary alcohols were synthesized and evaluated in the bromination reaction with MgBr 2 ·Et 2 O. The greater coordinating ability of the 2-pyridyl sulfonate esters accounted for its observed superior reactivity and selectivity. Reaction of neopentyl and phenyl 2-pyridyl sulfonates with a variety of aryl and heteroaryl Li reagents led to 2-substituted pyridines at temperatures as low as −78 °C via an S N Ar process. Mechanistic considerations are discussed.