Azirinium ylides from alkoxycarbonylcarbenoids and 2H-azirines: Generation and transformations

Khlebnikov, Alexander F.; Новиков, Михаил С.; Amer, A. A.; Kostikov, R. R.; Magull, J.; Vidović, Denis

doi:10.1134/s1070428006040075

Cited by 29 publications

(12 citation statements)

References 18 publications

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“…It should be noted that azadiene 3e in crystal exists in the s- trans- conformation across the single С–N bond (the С2–N1–С3–C4 dihedral angle is 4.3°, Fig. 1 ), unlike its C4-aryl-substituted analogs with the angle of 73–75° [ 26 ]. The Е -configuration of the С=N bond, unfavorable for cyclization into 1,4-oxazine, explains the enhanced thermal stability of compound 3e .…”

Section: Resultsmentioning

confidence: 99%

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

Ростовский¹,

Новиков²,

Khlebnikov³

et al. 2015

Beilstein J. Org. Chem.

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SummaryStrained azirinium ylides derived from 2H-azirines and α-diazoketones under Rh(II)-catalysis can undergo either irreversible ring opening across the N–C2 bond to 2-azabuta-1,3-dienes that further cyclize to 2H-1,4-oxazines or reversibly undergo a 1,5-cyclization to dihydroazireno[2,1-b]oxazoles. Dihydroazireno[2,1-b]oxazoles derived from 3-aryl-2H-azirines and 3-diazoacetylacetone or ethyl diazoacetoacetate are able to cycloadd to acetyl(methyl)ketene generated from 3-diazoacetylacetone under Rh(II) catalysis to give 4,6-dioxa-1-azabicyclo[3.2.1]oct-2-ene and/or 5,7-dioxa-1-azabicyclo[4.3.1]deca-3,8-diene-2-one derivatives. According to DFT calculations (B3LYP/6-31+G(d,p)), the cycloaddition can involve two modes of nucleophilic attack of the dihydroazireno[2,1-b]oxazole intermediate on acetyl(methyl)ketene followed by aziridine ring opening into atropoisomeric oxazolium betaines and cyclization. Azirinium ylides generated from 2,3-di- and 2,2,3-triaryl-substituted azirines give rise to only 2-azabuta-1,3-dienes and/or 2H-1,4-oxazines.

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Section: Resultsmentioning

confidence: 99%

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

Ростовский¹,

Новиков²,

Khlebnikov³

et al. 2015

Beilstein J. Org. Chem.

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“…Since the four-membered ring of a 2,3-dihydroazete is significantly strained, such cyclization is possible only when at least one substituent is present at the C4 of 2-azadiene and more favorable 1,5-or 1,6-cyclizations are difficult or impossible. In particular, 1,4-cyclization of 3,4-diphenylsubstituted azadiene 13 derived from 2,3-diphenyl-2H-azirine 10 and rhodium carbene 12 gave dihydroazete 14 in good yield under mild conditions (Scheme 2) [26,27]. The analogous reaction of azirine 10 with diazoamidoester 15 in 1,2-dichloroethane (DCE) resulted in the formation of dihydroazete 18 and revealed the stereoselective nature of both the formation of the intermediate azadiene 17 and its cyclization [28].…”

Section: 4-electrocyclization Of Azabutadienesmentioning

confidence: 99%

Electrocyclizations of Conjugated Azapolyenes Produced in Reactions of Azaheterocycles with Metal Carbenes

2021

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Conjugated azapolyenes (azabuta-1,3-dienes, aza-/diaza-/oxaza-/oxadiazahexa-1,3,5-trienes) are highly reactive in electrocyclization reactions, which makes them convenient precursors for the synthesis of a wide range of four-, five-, and six-membered nitrogen heterocycles that are of relevance for medicinal chemistry. Ring opening reactions of 2H-azirines and azoles containing an N–N or N–O bond, initiated by a transition metal carbene, have become increasingly important in recent years, since they easily allow the generation of azapolyenes with different numbers of double bonds and heteroatoms in various positions. This review summarizes the literature, published mainly in the last decade, on the synthetic and mechanistic aspects of electrocyclizations of azapolyenes generated by the carbene method.

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“…Cyclization of 242 (R 1 = R 3 = Ph; R 2 = H; X = Y = CO 2 Me) to azetine 243 was also observed and is probably favoured by strong polarization of the 2-aza-1,3-diene due to the presence of the two ester groups and a phenyl substituent (Scheme 72). 132,133 The Rh(II)-catalyzed reaction of 2H-azirines 236 with 2-acyl-2-diazoacetates 242 resulted in the formation of 2H-1,4-oxazines 244, probably via a 1,6-electrocyclization of the azadienes (E)-243 (Scheme 73). 134 3.1.2 3-Alkoxylcarbonyl-2-azabuta-1,3-dienes.…”

Section: Synthesis and Reactivity Of 1-sulfinyl-1-azabuta-13-dienesmentioning

confidence: 99%

Electron-deficient 1- and 2-azabuta-1,3-dienes: a comprehensive survey of their synthesis and reactivity

2011

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Electron-deficient 1- and 2-azabuta-1,3-dienes are reagents intrinsically able to provide a wide range of cyclic and acyclic N-containing building blocks. Depending on their substitution, they behave as dienes for Diels-Alder reactions, as partners for [4+1], [3+2], [2+2]-cycloadditions, for aziridinations and as electrophiles for 1,2 and 1,4-additions. Nowadays, they are a very versatile family of compounds, despite their usual instability and complex reactivity. Four decades of research in this challenging area are reviewed in this critical review: their synthetic aspects and their reactivity towards a wide range of dienophiles, dipoles and nucleophiles are described as well. The introduction focuses on their electronic properties in order to get a clear picture of their reactivity (190 references).

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Azirinium ylides from alkoxycarbonylcarbenoids and 2H-azirines: Generation and transformations

Cited by 29 publications

References 18 publications

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

Electrocyclizations of Conjugated Azapolyenes Produced in Reactions of Azaheterocycles with Metal Carbenes

Electron-deficient 1- and 2-azabuta-1,3-dienes: a comprehensive survey of their synthesis and reactivity

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