Lithium Naphthalenide-Induced Reductive Alkylation and Addition of Aryl- and Heteroaryl- Substituted Dialkylacetonitriles

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Lithium naphthalenide (LN)-induced reductive alkylation/addition reactions of aryl-, pyridyl-, and 2-thienyl-substituted dialkylacetonitriles have been investigated. Upon treatment with LN in THF at -40 ˚C, both aryl and pyridyl precursors could undergo the reductive decyanation smoothly, and the in situ generated carbanions could be readily trapped by alkyl halides, ketones, aldehydes, or even oxygen to afford a wide range of functionalized aromatic derivatives bearing a newly established quaternary carbon. To effect the desired reductive alkylation of 2-thienyldialkylacetonitriles, a much lower temperature such as -100 ˚C was required. Also with these substrates, an interesting ring-opening/S-alkylation process was observed when the reductive alkylation were performed at -78 ˚C to give 1-alkylsulfanyl-1,3,4-trienes. A mechanistic discussion is given for this observation.