Chemistry of four-membered cyclic nitrones. 1. Synthesis and thermal isomerization of 2,3-dihydroazete 1-oxides

Pennings, Marcel L. M.; Reinhoudt, David N.

doi:10.1021/jo00349a004

Cited by 50 publications

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“…Previously we have reported that reaction of the nitroalkenes 1 with ynamines 2 yields mixtures of N,N-dialkyl--4-nitro-I-cyclobuten-1 -amines 3 and four-membered cyclic nitrones 4 (Scheme 1) 26. These products can be regarded as being derived from a (2+2) and a ( 4 + 2 ) cycloaddition, respectively.…”

Section: Resultsmentioning

confidence: 99%

The (apparently disrotatory) thermal ring opening of 4‐nitro‐1‐cyclobuten‐1 ‐amines

Eijk

Overkempe

TROMPENAARS

et al. 1988

Recl. Trav. Chim. Pays‐Bas

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Abstract.A series of 4-nitro-1-cyclobuten-I-amines 3 was isolated from the thermal (2 + 2) cycloaddition of nitro(cyc1o)alkenes 1 and ynamines 2. Heating of 3a-d yielded products corresponding with disrotatory ring opening viz. the 1,3-dienes 6a-d. Heating of 3e,f at 60°C gave the dienes 7a,b, as the result of a conrotatory ring opening reaction, together with the trans-2-nitrocyclobutenes 8a,b, as the result of a hydrogen shift in the cyclobutene ring. Upon prolonged heating at 80°C 8b was converted into the diene 7b. Treatment of 3e with acid yielded the 2-nitrocyclobutenes 9a and 9b. The structures of 3a, 3f, 6a and 7b were elucidated by X-ray analysis. The formation of 6a-d is attributed to E/Z isomerization of the product, initially formed by a conrotatory ring opening. Introduction'

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Section: Resultsmentioning

confidence: 99%

The (apparently disrotatory) thermal ring opening of 4‐nitro‐1‐cyclobuten‐1 ‐amines

Eijk

Overkempe

TROMPENAARS

et al. 1988

Recl. Trav. Chim. Pays‐Bas

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“…1-nitroalkenes) with electronrich acetylenes (viz. ynamines) also takes place under mild conditions to give a 3nitrocyclobutene when the reactions are carried out in apolar solvents [6]. In more polar solvents these reactions give different products.…”

Section: Our Interest In This Reaction Stems From Experimental Resultmentioning

confidence: 99%

[2 + 2] Cycloadditions. A concerted pathway for acetylene plus ethylene

Hess

Schaad

Reinhoudt

1986

Int J of Quantum Chemistry

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“…Reinhoudt reported the first synthesis of stable azetidine nitrones 132 via the addition of an electron‐rich ynamine to a nitroalkene followed by rearrangement (Scheme A) . While nitrocyclobutenes 131 and 2‐azadiene‐ N ‐oxides 133 were observed as competing byproducts when these transformations were run in petroleum ether, linear E ‐nitroalkenes were shown to favor the formation of azetidine nitrones 132 as single diastereomers and increased yields were observed in more polar solvents such as acetonitrile . The proposed mechanism for this transformation proceeds via a formal [4+2]‐cycloaddition between nitroalkene 127 and ynamine 128 to give 130 followed by N–O bond cleavage and azetidine cyclization.…”

Section: Development Of Unsaturated Azetidines As Precursors For Divementioning

confidence: 99%

Divergent Functionalizations of Azetidines and Unsaturated Azetidines

Reidl

Anderson

2019

Asian J Org Chem

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Azetidines are unusual heterocyclic motifs that comprise key components of biologically active molecules and provide desirable structural properties for drug discovery. While a variety of methods have been designed for the synthesis of azetidines, screening and optimization studies often require systematic and versatile strategies for varying structural characteristics. With this need in mind, this review surveys methods for the divergent preparation of substituted azetidines from starting materials that contain a 4-membered azacycle. The scope and tolerance of azetidine functionalization reactions are described including approaches such as lithiation and electrophilic trapping, nucleophilic displacement, and transition metal catalysis. To complement this discussion, opportunities for using unsaturated azetidines as precursors to functionalized saturated analogues are also examined as an emerging alternative tactic towards the diversity-oriented preparation of these strained heterocycles. The aim of this Minireview is to identify recent advances, as well as areas where further development is needed, to continue to inspire innovative solutions to the divergent synthesis of functionalized azetidines.[a] T.

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Chemistry of four-membered cyclic nitrones. 1. Synthesis and thermal isomerization of 2,3-dihydroazete 1-oxides

Cited by 50 publications

References 0 publications

The (apparently disrotatory) thermal ring opening of 4‐nitro‐1‐cyclobuten‐1 ‐amines

The (apparently disrotatory) thermal ring opening of 4‐nitro‐1‐cyclobuten‐1 ‐amines

[2 + 2] Cycloadditions. A concerted pathway for acetylene plus ethylene

Divergent Functionalizations of Azetidines and Unsaturated Azetidines

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