Acylated 2,2-dimethylaziridines

regioselectivity of ring opening by sodium thiophenolate; borderline SN2 due to planarization of nitrogen pyramid

Pen yuan Lin, Konstantinos Bellos, Helmut Stamm, Andreas Onistschenko

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

2,2-Dimethylaziridines 1 carrying a COR group on nitrogen are opened by PhS⊖ with a regioselectivity RS = abnormal:normal ≥ 20 in MeOH and 5-16 in THF. Practically no influence of COR on RS was found except for the poorest oxidant 1g (R = tBu) that gave the highest RS (95, MeOH). This rules out an SET mechanism for the abnormal opening. Absence of homolytic ring opening is directly shown by the failure to detect products resulting from cyclization of a homolytically formed radical when COR is cinnamoyl (1f). Direct nucleophilic attack is indicated by suppression of any reaction with PhS⊖ when the steric hindrance is increased (N-benzoylaziridine 13). The observed SN2 borderline behaviour with 1 is explained by reaction in a flattened nitrogen conformation of the otherwise poorly reactive 1. Carboxamide resonance in this (nearly) planar conformation generates a substantial positive charge on N which will shift the mechanism closer to SN1 by partial heterolysis of the N-CMe2 bond prior to attack by PhS⊖.

Original languageEnglish
Pages (from-to)2359-2372
Number of pages14
JournalTetrahedron
Volume48
Issue number12
DOIs
Publication statusPublished - Mar 20 1992
Externally publishedYes

Fingerprint

Regioselectivity
Conformations
Nitrogen
Sodium
Cyclization
Oxidants

Keywords

  • aziridines
  • leaving group quality of N-acylaziridines
  • nucleophilic attack
  • planation of N pyramid.
  • preferred abnormal opening

ASJC Scopus subject areas

  • Biochemistry
  • Organic Chemistry
  • Drug Discovery

Cite this

Acylated 2,2-dimethylaziridines : regioselectivity of ring opening by sodium thiophenolate; borderline SN2 due to planarization of nitrogen pyramid. / Lin, Pen yuan; Bellos, Konstantinos; Stamm, Helmut; Onistschenko, Andreas.

In: Tetrahedron, Vol. 48, No. 12, 20.03.1992, p. 2359-2372.

Research output: Contribution to journalArticle

Lin, Pen yuan ; Bellos, Konstantinos ; Stamm, Helmut ; Onistschenko, Andreas. / Acylated 2,2-dimethylaziridines : regioselectivity of ring opening by sodium thiophenolate; borderline SN2 due to planarization of nitrogen pyramid. In: Tetrahedron. 1992 ; Vol. 48, No. 12. pp. 2359-2372.
@article{10b181d8c6fd47ad8826e4088c0cdc3b,
title = "Acylated 2,2-dimethylaziridines: regioselectivity of ring opening by sodium thiophenolate; borderline SN2 due to planarization of nitrogen pyramid",
abstract = "2,2-Dimethylaziridines 1 carrying a COR group on nitrogen are opened by PhS⊖ with a regioselectivity RS = abnormal:normal ≥ 20 in MeOH and 5-16 in THF. Practically no influence of COR on RS was found except for the poorest oxidant 1g (R = tBu) that gave the highest RS (95, MeOH). This rules out an SET mechanism for the abnormal opening. Absence of homolytic ring opening is directly shown by the failure to detect products resulting from cyclization of a homolytically formed radical when COR is cinnamoyl (1f). Direct nucleophilic attack is indicated by suppression of any reaction with PhS⊖ when the steric hindrance is increased (N-benzoylaziridine 13). The observed SN2 borderline behaviour with 1 is explained by reaction in a flattened nitrogen conformation of the otherwise poorly reactive 1. Carboxamide resonance in this (nearly) planar conformation generates a substantial positive charge on N which will shift the mechanism closer to SN1 by partial heterolysis of the N-CMe2 bond prior to attack by PhS⊖.",
keywords = "aziridines, leaving group quality of N-acylaziridines, nucleophilic attack, planation of N pyramid., preferred abnormal opening",
author = "Lin, {Pen yuan} and Konstantinos Bellos and Helmut Stamm and Andreas Onistschenko",
year = "1992",
month = "3",
day = "20",
doi = "10.1016/S0040-4020(01)88757-3",
language = "English",
volume = "48",
pages = "2359--2372",
journal = "Tetrahedron",
issn = "0040-4020",
publisher = "Elsevier Limited",
number = "12",

}

TY - JOUR

T1 - Acylated 2,2-dimethylaziridines

T2 - regioselectivity of ring opening by sodium thiophenolate; borderline SN2 due to planarization of nitrogen pyramid

AU - Lin, Pen yuan

AU - Bellos, Konstantinos

AU - Stamm, Helmut

AU - Onistschenko, Andreas

PY - 1992/3/20

Y1 - 1992/3/20

N2 - 2,2-Dimethylaziridines 1 carrying a COR group on nitrogen are opened by PhS⊖ with a regioselectivity RS = abnormal:normal ≥ 20 in MeOH and 5-16 in THF. Practically no influence of COR on RS was found except for the poorest oxidant 1g (R = tBu) that gave the highest RS (95, MeOH). This rules out an SET mechanism for the abnormal opening. Absence of homolytic ring opening is directly shown by the failure to detect products resulting from cyclization of a homolytically formed radical when COR is cinnamoyl (1f). Direct nucleophilic attack is indicated by suppression of any reaction with PhS⊖ when the steric hindrance is increased (N-benzoylaziridine 13). The observed SN2 borderline behaviour with 1 is explained by reaction in a flattened nitrogen conformation of the otherwise poorly reactive 1. Carboxamide resonance in this (nearly) planar conformation generates a substantial positive charge on N which will shift the mechanism closer to SN1 by partial heterolysis of the N-CMe2 bond prior to attack by PhS⊖.

AB - 2,2-Dimethylaziridines 1 carrying a COR group on nitrogen are opened by PhS⊖ with a regioselectivity RS = abnormal:normal ≥ 20 in MeOH and 5-16 in THF. Practically no influence of COR on RS was found except for the poorest oxidant 1g (R = tBu) that gave the highest RS (95, MeOH). This rules out an SET mechanism for the abnormal opening. Absence of homolytic ring opening is directly shown by the failure to detect products resulting from cyclization of a homolytically formed radical when COR is cinnamoyl (1f). Direct nucleophilic attack is indicated by suppression of any reaction with PhS⊖ when the steric hindrance is increased (N-benzoylaziridine 13). The observed SN2 borderline behaviour with 1 is explained by reaction in a flattened nitrogen conformation of the otherwise poorly reactive 1. Carboxamide resonance in this (nearly) planar conformation generates a substantial positive charge on N which will shift the mechanism closer to SN1 by partial heterolysis of the N-CMe2 bond prior to attack by PhS⊖.

KW - aziridines

KW - leaving group quality of N-acylaziridines

KW - nucleophilic attack

KW - planation of N pyramid.

KW - preferred abnormal opening

UR - http://www.scopus.com/inward/record.url?scp=0026568993&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0026568993&partnerID=8YFLogxK

U2 - 10.1016/S0040-4020(01)88757-3

DO - 10.1016/S0040-4020(01)88757-3

M3 - Article

VL - 48

SP - 2359

EP - 2372

JO - Tetrahedron

JF - Tetrahedron

SN - 0040-4020

IS - 12

ER -