Alkene Isomerisation Catalysed by a Superbasic Sodium Amide.

Typically catalysed by transition metals, alkene isomerisation is a powerful  methodology for preparation of internal olefins. In contrast, the use of more earth abundant main group reagents is limited to activated substrates, requiring high temperatures and excess stoichiometric amounts. Opening a new portal for progressing this field, here we report applications of bulky sodium amide NaTMP (TMP = 2,2,6,6-tetramethylpiperidide) when partnered by tridentate Lewis donor PMDETA (N,N,N',N'',N''-pentamethyldiethylenetriamine) in catalytic alkene isomerisation of terminal olefins under mild reaction conditions. An array of distinct olefins could successfully be isomerised, including unactivated olefins, allylamines and allylethers, showing the high activity of this partnership. In-depth mechanistic insights provided by X-ray crystallography, real-time nuclear magnetic resonance (NMR) monitoring, and density functional theory (DFT) calculations have unveiled the crucial role of in-situ-generated TMP(H) in facilitating efficient isomerisation and the choice of alkali-metal. Additionally, theoretical studies shed light on the observed E/Z selectivity, particularly accounting for selective formation of Z-vinyl ethers. The versatility of our method is further demonstrated through isomerisation of unactivated cycloalkenes, which undergo hydrogen isotope exchange to produce deuterated compounds.

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