Reductive lithiation nitriles

In the study involving a tetrahydropyranyl radical illustrated in Scheme 10.17, Rychnovsky was attempting to establish whether cyclisation was from the radical or the anionic intermediate in the reductive lithiation of nitrile 11 to give 14. The radical intermediate, 12,... 

A similar reaction presumably underlies one of the most remarkable transformations yet achieved by reductive lithiation with catalytic DBB the transformation of a nitrile into an organolithium with cleavage of a C-C bond.99 The electrophile needs to be present in the reaction mixture (Barbier conditions), but silylation or reaction with a carbonyl compound competes successfully with deprotonation of the nitrile starting material ... 

As expected, only few examples involving carbon-carbon bond cleavage have been described in the literature. Namely, only nitriles and A-methoxycarboxamides undergo a reductive carbon-carbon bond cleavage by lithiation under arene-catalyzed conditions. 

E)-Allylic amines. Reaction of the lithiated methylphosphonate ester with a nitrile, followed by addition of an aldehyde, furnishes a conjugated imine with an ( )-configuration. Immediate reduction (e.g., with NaBH4) gives the allylic amine. 

We next examined the reactivity of the stable iminium ion 63a (Scheme 27). When the iminium 63a was treated with NaOAc or NaNs, only the starting material was recovered. The reaction of 63a with -BuLi or lithiated dithiane gave complex mixtures. The stronger basic nucleophiles, like -BuLi and lithiated dithiane, may attack both the iminium carbon (C23) and the hyperconjugated carbons (C5) to give complex mixtures (Fig. 17). However, the reduction of iminium 63a with NaBH4 afforded the saturated propellane derivative 69. The reaction of iminium 63a with NaCN ° provided nitrile 70 then reduction of the nitrile 70 produced amine 71 in a... 

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