Aziridines. 59. Regioselectivity in nucleophilic Ring Opening of 2‐Methylaziridines. Lag of bond making as model for the abnormal opening

Pen‐Yuan ‐Y Lin; Gunther Bentz; H. Stamm

doi:10.1002/prac.19933350105

Aziridines. 59. Regioselectivity in nucleophilic Ring Opening of 2‐Methylaziridines. Lag of bond making as model for the abnormal opening

Pen‐Yuan ‐Y Lin, Gunther Bentz, H. Stamm

Research output: Contribution to journal › Article › peer-review

18 Citations (Scopus)

Abstract

The regioselectivity ratio RS = normal: abnormal opening of activated 2‐methylaziridines 2 by nucleophiles is found to range from 0.10 to unmeasurable large (only normal opening = substitution at CH₂ by strongly basic carbanions). RS is assumed to result from S_N2 variants differing in the degree to which bond breaking is ahead of bond making including perhaps synchronous S_N2. Bond breaking will be more ahead for the N‐CMe bond. High nucleophilic power pushes bond making toward a synchronous process resulting in great RS. The decrease in RS with acyl activation relative to sulfonyl activation is in accord with a flattening of the nitrogen pyramid (planarization effect). The planarization effect is retained in acidic medium by O‐protonation: Rs 0.10–0.14 for methanolysis as compared to RS 0.43 for N‐protonated sulfonylaziridine 2h. AM1 calculations support the planarization hypothesis. – No indication for SET with trityl anion was found.

Original language	English
Pages (from-to)	23-34
Number of pages	12
Journal	Advanced Synthesis and Catalysis
Volume	335
Issue number	1
DOIs	https://doi.org/10.1002/prac.19933350105
Publication status	Published - 1993
Externally published	Yes

ASJC Scopus subject areas

General Chemistry

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title = "Aziridines. 59. Regioselectivity in nucleophilic Ring Opening of 2‐Methylaziridines. Lag of bond making as model for the abnormal opening",

abstract = "The regioselectivity ratio RS = normal: abnormal opening of activated 2‐methylaziridines 2 by nucleophiles is found to range from 0.10 to unmeasurable large (only normal opening = substitution at CH2 by strongly basic carbanions). RS is assumed to result from SN2 variants differing in the degree to which bond breaking is ahead of bond making including perhaps synchronous SN2. Bond breaking will be more ahead for the N‐CMe bond. High nucleophilic power pushes bond making toward a synchronous process resulting in great RS. The decrease in RS with acyl activation relative to sulfonyl activation is in accord with a flattening of the nitrogen pyramid (planarization effect). The planarization effect is retained in acidic medium by O‐protonation: Rs 0.10–0.14 for methanolysis as compared to RS 0.43 for N‐protonated sulfonylaziridine 2h. AM1 calculations support the planarization hypothesis. – No indication for SET with trityl anion was found.",

author = "Lin, {Pen‐Yuan ‐Y} and Gunther Bentz and H. Stamm",

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AU - Lin, Pen‐Yuan ‐Y

AU - Bentz, Gunther

AU - Stamm, H.

PY - 1993

Y1 - 1993

N2 - The regioselectivity ratio RS = normal: abnormal opening of activated 2‐methylaziridines 2 by nucleophiles is found to range from 0.10 to unmeasurable large (only normal opening = substitution at CH2 by strongly basic carbanions). RS is assumed to result from SN2 variants differing in the degree to which bond breaking is ahead of bond making including perhaps synchronous SN2. Bond breaking will be more ahead for the N‐CMe bond. High nucleophilic power pushes bond making toward a synchronous process resulting in great RS. The decrease in RS with acyl activation relative to sulfonyl activation is in accord with a flattening of the nitrogen pyramid (planarization effect). The planarization effect is retained in acidic medium by O‐protonation: Rs 0.10–0.14 for methanolysis as compared to RS 0.43 for N‐protonated sulfonylaziridine 2h. AM1 calculations support the planarization hypothesis. – No indication for SET with trityl anion was found.

AB - The regioselectivity ratio RS = normal: abnormal opening of activated 2‐methylaziridines 2 by nucleophiles is found to range from 0.10 to unmeasurable large (only normal opening = substitution at CH2 by strongly basic carbanions). RS is assumed to result from SN2 variants differing in the degree to which bond breaking is ahead of bond making including perhaps synchronous SN2. Bond breaking will be more ahead for the N‐CMe bond. High nucleophilic power pushes bond making toward a synchronous process resulting in great RS. The decrease in RS with acyl activation relative to sulfonyl activation is in accord with a flattening of the nitrogen pyramid (planarization effect). The planarization effect is retained in acidic medium by O‐protonation: Rs 0.10–0.14 for methanolysis as compared to RS 0.43 for N‐protonated sulfonylaziridine 2h. AM1 calculations support the planarization hypothesis. – No indication for SET with trityl anion was found.

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Aziridines. 59. Regioselectivity in nucleophilic Ring Opening of 2‐Methylaziridines. Lag of bond making as model for the abnormal opening

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