Loss of chirality through facile lewis base mediated aza-enolate formation in Na and K (S)-N-(α-Methylbenzyl)methallylamides

Matthew T Flynn, Rachel A Stott, Victoria L Blair, Philip C Andrews

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4 Citations (Scopus)

Abstract

Metalation of (S)-N-(α-methylbenzyl)methallylamine with nBuM (M = Li, Na, or K) in hexane leads to the allylic metal amides [(S)-PhCH(CH3)N(CH2C{CH3}=CHLi)Li]6, 1, [(S)-PhCH(CH3)N(CH2C{CH3}=CH2)Na]n, and [(S)-PhCH(CH3)N(CH2C{CH3}=CH2)K]n, 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(=CH2)N(CH2CH{CH3}2)Na], 2, [PhC(=CH2)N(CH2CH{CH3}2)Na·TMEDA]n, 3, [PhC(=CH2)N(CH2CH{CH3}2)Na·PMDETA]n, 4, and [PhC(=CH2)N(CH2CH{CH3}2)K]n, 5, resulting in loss of chirality. In contrast, the addition of benzene leads exclusively to the 1-aza-allyl complexes [(S)-PhCH(CH3)N(CH=C{CH3}2)Na]n, 6, and [(S)-PhCH(CH3)N(CH=C{CH3}2)K]n, 7, both of which are not observed in the presence of Lewis donors. Doping a benzene solution of 7 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 1 and 2 also being characterized by single-crystal X-ray diffraction. Rearrangement to the aza-enolates 2 and 3 is unprecedented under the conditions employed.

Original languageEnglish
Pages (from-to)2707-2714
Number of pages8
JournalOrganometallics
Volume35
Issue number16
DOIs
Publication statusPublished - 22 Aug 2016

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