10.1021/acs.organomet.6b00445.s002
Matthew
T. Flynn
Matthew
T.
Flynn
Rachel Stott
Rachel
Stott
Victoria L. Blair
Victoria L.
Blair
Philip C. Andrews
Philip C.
Andrews
Loss of Chirality through Facile Lewis Base Mediated
Aza-enolate Formation in Na and K (<i>S</i>)‑<i>N</i>‑(α-Methylbenzyl)methallylamides
American Chemical Society
2016
n BuM
benzene solution
anion rearrangement
THF
complexes 1
Lewis base
K amides
Na
PhCH
CH
PMDETA
TMEDA
Lewis donors
PhC
NMR spectroscopy
2016-08-09 15:54:28
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Loss_of_Chirality_through_Facile_Lewis_Base_Mediated_Aza-enolate_Formation_in_Na_and_K_i_S_i_i_N_i_-Methylbenzyl_methallylamides/3555909
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(CHC{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(CHC{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.