Nucleophilic cleavage of 2,2-dimethylaziridines: competition between SN2 and postulated “SET” mechanism.

Stamm, H.; Assithianakis, P.; Buchholz, B.; Weiβ, R.

doi:10.1016/s0040-4039(00)85562-8

Cited by 56 publications

(16 citation statements)

References 8 publications

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“…For example, N-ethoxycarbonylaziridines undergo facile ring opening with aniline. 13 Again, 1-ethoxycarbonyl-2-trimethylsilylaziridine failed to undergo ring opening with the range of nucleophiles previously mentioned. When reaction was observed it usually involved loss of the ethoxycarbonyl group.…”

Section: Ring Opening With Nucleophilic Reagentsmentioning

confidence: 93%

“…In such cases quaternisation of the nitrogen is not necessary, however, the regiochemistry of ring opening still depends upon the substituents on the ring carbons, the conditions and the nucleophile. 13 Ring opening reactions of aziridines have been recently reviewed by Tanner. 14 These observations suggest that the presence of a 2-trialkylsilyl substituent in an aziridine should favour attack α to the silicon if the reaction proceeds via an S N 2 type route.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Ring opening reactions of 2-trialkylsilylaziridines

Bassindale¹,

Kyle²,

Soobramanien³

et al. 2000

J. Chem. Soc., Perkin Trans. 1

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Section: Ring Opening With Nucleophilic Reagentsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Ring opening reactions of 2-trialkylsilylaziridines

Bassindale¹,

Kyle²,

Soobramanien³

et al. 2000

J. Chem. Soc., Perkin Trans. 1

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“…Similarly, while indole-Li and 124-S provide only normal N-substitution in THF/ether in accord with a reaction of the highly nucleophilic N-anion, in toluene (no dissociation) this product arises in 29% yield only while substitution in position 3 (very poor Nu -) proceeds with 49% abnormal and 16% normal NRO [71]. The said hypothesis on the abnormal NRO [76] consisted of SET, homolytic ring opening and radical coupling or more complicated processes as realized in reactions of Trwith Az's 124-A (even with 124-Aa) [78] whose three Tr containing products are shown in Sche- [84] no difference in RS for 124-A or other acylaziridines is so far known between products of real NRO and those from all kinds of pseudo NRO but one should be aware that a conformation dependent stereoelectronic effect (cf. [8]) may change RS of homolytic ring opening for trans-Az's of type trans-109b.…”

Section: Scheme 19 C-amidoethylation Of Simple Nitrilesmentioning

confidence: 86%

Nucleophilic ring opening of aziridines

Stamm

1999

J. prakt. Chem.

102

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This account of research work on nucleophilic ring opening (NRO) of aziridines (Az's) demonstrates the broad synthetic scope of this reaction, inclusive secondary reactions, and it discusses the special mechanistic fundamentals and details as well as mechanistic variants. Formation of a C–C bond by NRO is the red thread in this report. A central mechanistic aspect is the quality of the leaving group in Az bases, aziridinium ions and activated Az's (acyl, sulfonyl; double activation). Factors controlling the regioselectivity of NRO are dealt with as well as the influence of the nitrogen pyramid. Competing reactions include carbonyl attack (acylated Az's) and electron transfer with cases of pseudo‐NRO (multistep radical paths).

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“…The necessary water was introduced with the acid. The other by products, 2-oxazolines 12 (runs [14][15][16][17][18] and methallylamine Bf (runs [21][22][23][24][25], originate from branches of the SN I path. The acid catalyzed isomerization of N-acylaziridines to oxazolines [27] was shown to be consistent with a carbenium intermediate when stabilized by structure or solvent [28J.…”

Section: Acid Catalyzed Alcoholysismentioning

confidence: 99%

Reactions with Aziridines, XXXII[1]. Mechanistic Aspects in Nucleophilic Opening of Three‐Membered Rings. Alcoholyses of Activated Aziridines

Bucholz

Stamm

1986

Israel Journal of Chemistry

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Nucleophilic ring opening of three‐membered rings is discussed in terms of leaving group basicity. Reactions of activated (weakly basic leaving groups) 2,2‐dimethylaziridines 5 and 2‐phenylaziridines 6 with alcohols ROH are studied with reference to the site selectivity of ring opening and competing side‐reactions. Abnormal opening (at the substituted carbon) of 5 proceeds in neutral ROH without catalyst when the activation is strong (tosyl) whilst no reaction or mainly carbonyl attack is observed with weak activation (CONHAr). NaClO4 catalyzes the abnormal opening of 5. EtO− gives exclusively normal opening of 5 whilst, in contrast to the literature, MeO− gives also a substantial amount of abnormal ether. Attack on 6 always occurs at both positions with the predominance of the abnormal reaction being greater for MeO− than for EtO−. These reactions are considered SN2 with steric and benzylic differentiation between normal and abnormal attack depending on the size of ROH. Acid catalyzed openings of 5 and 6 proceed exclusively abnormally in the ether‐forming reaction as well as in side‐reactions. Competition experiments and increase of the side‐reactions with the size of ROH demonstrate a deceleration of the ether‐forming reaction with the size of ROH. Obviously, the side‐reactions originate from a carbenium ion whilst the ethers are mainly formed by a borderline mechanism. R(‐)6b and acidic MeOH give only 8% racemization in the abnormal ether. An order of activation is proposed for activated aziridines under acid catalysis (double activation).

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Nucleophilic cleavage of 2,2-dimethylaziridines: competition between SN2 and postulated “SET” mechanism.

Cited by 56 publications

References 8 publications

Ring opening reactions of 2-trialkylsilylaziridines

Ring opening reactions of 2-trialkylsilylaziridines

Nucleophilic ring opening of aziridines

Reactions with Aziridines, XXXII[1]. Mechanistic Aspects in Nucleophilic Opening of Three‐Membered Rings. Alcoholyses of Activated Aziridines

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