Pyridynes alkylation

Hydrogen attached to ring carbon atoms of neutral azines, and especially azinium cations, is acidic and can be replaced by a metal formally being removed as a proton. Alkyllithiums can be used as bases for this purpose however, the reaction can be accompanied by addition of the alkyl anion to the ring C=N bond. To avoid this, sterically hindered bases with strong basicity but low nucleophilicity can be utilized. Among these are lithium tetramethylpiperidide (LiTMP) and lithium diisopropylamide (LDA). If the anion contains an ortho halogen atom, then this can be eliminated to form a pyridyne (see Section 3.2.3.10.1). 

Although most chemists refer to 1 as benzyne and to 2 as 3-pyridyne, one will not find these names in Chemical Abstracts (CA). Benzyne is listed there as l,3-cyclohexadiene-5-yne, and under this heading one can also find various substituted benzynes (alkyl, halo, etc.). Although this name emphasizes the appropriateness of benzyne to this volume on the... 

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