Loss of Chirality through Facile Lewis Base Mediated Aza-enolate Formation in Na and K (<i>S</i>)‑<i>N</i>‑(α-Methylbenzyl)methallylamides

Metalation of (<i>S</i>)-<i>N</i>-(α-methylbenzyl)­methallylamine with <i>n</i>BuM (M = Li, Na, or K) in hexane leads to the allylic metal amides [(<i>S</i>)-PhCH­(CH<sub>3</sub>)­N­(CH<sub>2</sub>C­{CH<sub>3</sub>}CHLi)­Li]<sub>6</sub>, <b>1</b>, [(<i>S</i>)-PhCH­(CH<sub>3</sub>)­N­(CH<sub>2</sub>C­{CH<sub>3</sub>}CH<sub>2</sub>)­Na]<sub><i>n</i></sub>, and [(<i>S</i>)-PhCH­(CH<sub>3</sub>)­N­(CH<sub>2</sub>C­{CH<sub>3</sub>}CH<sub>2</sub>)­K]<sub><i>n</i></sub>, respectively. The addition of any Lewis base (here THF, TMEDA, or PMDETA) to the Na and K amides promotes rapid anion rearrangement to the aza-enolate complexes [PhC­(CH<sub>2</sub>)­N­(CH<sub>2</sub>CH­{CH<sub>3</sub>}<sub>2</sub>)­Na]<sub>∞</sub>, <b>2</b>, [PhC­(CH<sub>2</sub>)­N­(CH<sub>2</sub>CH­{CH<sub>3</sub>}<sub>2</sub>)­Na·TMEDA]<sub><i>n</i></sub>, <b>3</b>, [PhC­(CH<sub>2</sub>)­N­(CH<sub>2</sub>CH­{CH<sub>3</sub>}<sub>2</sub>)­Na·PMDETA]<sub><i>n</i></sub>, <b>4</b>, and [PhC­(CH<sub>2</sub>)­N­(CH<sub>2</sub>CH­{CH<sub>3</sub>}<sub>2</sub>)­K]<sub><i>n</i></sub>, <b>5</b>, resulting in loss of chirality. In contrast, the addition of benzene leads exclusively to the 1-aza-allyl complexes [(<i>S</i>)-PhCH­(CH<sub>3</sub>)­N­(CHC­{CH<sub>3</sub>}<sub>2</sub>)­Na]<sub><i>n</i></sub>, <b>6</b>, and [(<i>S</i>)-PhCH­(CH<sub>3</sub>)­N­(CHC­{CH<sub>3</sub>}<sub>2</sub>)­K]<sub><i>n</i></sub>, <b>7</b>, both of which are not observed in the presence of Lewis donors. Doping a benzene solution of <b>7</b> with THF gives the first observation of reorganization to the intermediate 2-aza-allyl anion. All seven complexes have been characterized by NMR spectroscopy, with complexes <b>1</b> and <b>2</b> also being characterized by single-crystal X-ray diffraction. Rearrangement to the aza-enolates <b>2</b> and <b>3</b> is unprecedented under the conditions employed.