Synthesis and Aza-[2,3]-Wittig Rearrangements of Vinylaziridines:  Scope and Limitations

Abstract

cis- and trans-2,3-Trisubstituted vinylaziridines have been prepared from cis- and trans-epoxy alcohols, respectively, and used as substrates in the aza-[2,3]-Wittig rearrangement. Five different anion-stabilizing groups have been investigated for their efficiency to promote the rearrangement, and it was found that N-tert-butyl acetyl vinylaziridines were superior in this reaction, affording the corresponding cis-2,6-tetrahydropyridines (>90%) as single isomers when treated with LDA. Similarly, the corresponding (Z)-propenylaziridines gave trans,trans-2,3,6-trisubstituted tetrahydropyridines as the sole products while the (E)-propenylaziridines afforded the cis,cis-2,3,6-derivatives with equally high selectivity. The scope and limitations of the process have been investigated by varying the structure of the substrate, and the mechanism of the rearrangement has been probed to some extent; the mechanistic picture is more complex than assumed previously.

Investigations of the [2,3]-Sigmatropic Rearrangements of Vinylaziridines and Allylic Amines

“…9 The activating, anion-stabilizing group needed for the projected rearrangement was subsequently introduced by N-alkylation with tert-butyl bromoacetate, benzyl bromide, bromoacetonitrile or propargyl bromide, and subsequent deprotection gave alcohol 7. 10 Much to our surprise, when initially performing the Swern oxidation-Wittig olefination sequence on alcohol 7a (R = t-Bu, R 1 = Ph) none of the expected vinylaziridine 3a (R = t- …”

“…Of particular interest is the stereoselectivity of the rearrangement of vinylaziridines 3g,h,j,k,m (entries 2, 3, 5, 6, 8). 10 In each case the stereochemical information supplied by the olefin is retained throughout the reaction, resulting in formation of trans,trans-2,3,6-trisubstituted tetrahydropyridines when starting from a Z-olefin (entries 2, 5, 8), while substrates containing an E-olefin moiety are transformed into cis,cis-2,3,6-trisubstituted tetrahydropyridines (entries 3, 6). Normally such high selectivities in rearrangement reactions are indicative of a concerted mechanism, and we originally proposed such reaction pathway.…”

Recentes avanços na preparação de aziridinas. Aplicações sintéticas e implicações mecanísticas

“…Além disso, o emprego de aminoálcoois como precursores sintéticos pode causar sérias dificuldades experimentais, devido à alta reatividade do grupamento amino frente a eletrófilos. Uma alternativa interessante 39 para preparação de NH-aziridinas reside na reação entre β-azidoálcoois e fosfinas, formando intermediários oxazafosforanos cíclicos que sofrem rearranjo para as aziridinas correspondentes 40,41 , com eliminação de óxido de fosfina e sob condições essencialmente neutras. Dessa forma, a reação entre trifenilfosfina e β-azidoálcoois 17, convenientemente preparados a partir da abertura de epóxidos ou sulfatos/sulfonatos cíclicos com íon azoteto (N 3 -), produz as respectivas trans-aziridinas 18, utilizadas na sínte-se de aminoácidos não-naturais 42 (Esquema 9).…”

Rearrangement of N‐Aryl‐2‐Vinylaziridines to Benzoazepines and Dihydropyrroles: A Synthetic and Theoretical Study

“…[17][18][19] The chemical behavior of C-vinylaziridines is modulated by the nature of the substituent on the nitrogen atom and, in general, the presence of a benzyl group or of strong electronegative functionalities, such as a tosyl or acyl group, improves their reactivity towards nucleophiles. [4,5,7,[20][21][22] C-Vinylaziridines can also undergo several pericyclic reactions in which a s bond is shifted over a p system to yield heterocyclic compounds, such as 3-pyrrolines, [23,24] tetrahydropyridines, [14,[25][26][27][28] lactams, [29][30][31] and benzoazepines. These last products are formed by [3,3]-Claisen rearrangements of the corresponding N-aryl-2-vinylaziridines.…”