Chemistry of 5-oxodihydroisoxazoles. Part 18.1 Synthesis of oxazoles by the photolysis and pyrolysis of 2-acyl-5-oxo-2,5-dihydroisoxazoles

Prager, R. H.; Smith, Jason A.; Weber, B.; Williams, Craig M.

doi:10.1039/a700134g

Cited by 33 publications

(11 citation statements)

References 36 publications

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“…132 N-Acylisoxazolones 85 lose carbon dioxide on flash pyrolysis or on photolysis to give trisubstituted oxazoles 86. 133,134 When N-thioacylisoxazoles are used instead, they give thiazoles in an analogous manner. 135 5-Arylisoxazole-4-carbaldehydes have been isolated in moderate yield from the reaction of aryl 2-azidomethyl ketones with the Vilsmeier reagent at 80-90 ЊC.…”

Section: Oxazoles Thiazoles and Benzothiazolesmentioning

confidence: 99%

Synthesis of aromatic heterocycles

Gilchrist¹

1999

J. Chem. Soc., Perkin Trans. 1

200

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Section: Oxazoles Thiazoles and Benzothiazolesmentioning

confidence: 99%

Synthesis of aromatic heterocycles

Gilchrist¹

1999

J. Chem. Soc., Perkin Trans. 1

200

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“…There have been many synthetic efforts to develop efficient and mild methodologies for the preparation of oxazoles. These include, among others, the Cornforth protocol,3 catalytic decomposition of α‐diazocarbonyl compounds,4 photolysis and pyrolysis of N ‐acylisoxazolones5 and modified Robinson–Gabriel reactions 6. Wipf and co‐workers7 reported the synthesis of oxazoles by treatment of serine derivatives with diethylaminosulfur trifluoride (DAST) followed by bromotrichloromethane and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU).…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Substituted Oxazoles from N‐Acyl‐β‐hydroxyamino Acid Derivatives

2008

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Several N-acyl-β-hydroxyamino acids were prepared and treated with di-tert-butyl dicarbonate in the presence of 4-(dimethylamino)pyridine, followed by treatment with N,N,NЈ,NЈ-tetramethylguanidine to give the corresponding N-acyldehydroamino acids in good to high yields. These were then treated with I 2 /K 2 CO 3 followed by 1,8-diazabicyclo[5.4.0]undec-7-ene. The methyl esters of N-acyldehydroaminobutyric acid gave the corresponding substituted oxazoles in good to high yields. The N-acyldehydrophenylalanines gave 5-phenyloxazole derivatives in low to moderate yields together with β-iododehydrophenylalanines. Under the same conditions, N-acyldehydroalanines failed to give the corresponding oxazoles. However, when the reac-

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“…Another methodology for the synthesis of oxazoles takes advantage of the photochemical reactivity of N-acyl-isoxazolin-5-ones 86. The irradiation of these compounds is performed on a preparative scale in either acetonitrile (at 254 nm) or in acetone (at 300 nm), and the final oxazoles 87 are obtained in moderate to excellent yields, depending on the substrate and the irradiation conditions (Scheme 12.25) [56]. This strategy appears generally applicable to the synthesis of a large variety of 2-substituted targets, which can be obtained by simply using the appropriate acylating reagent on the isoxazolin-5-ones to form 86 that will be subsequently irradiated.…”

Section: Oxazolesmentioning

confidence: 99%

“…This strategy appears generally applicable to the synthesis of a large variety of 2-substituted targets, which can be obtained by simply using the appropriate acylating reagent on the isoxazolin-5-ones to form 86 that will be subsequently irradiated. Among other interesting examples are the synthesis of bis-oxazole 89, the precursor of tris-oxazole 90 [56], and of 2-(1-aminoalkyl)oxazoles 93 (Scheme 12.25) [57,58]. The latter compounds are obtained without significant racemization at the stereogenic center by a sequence of reactions consisting of N-acylation of the appropriate isoxazolin-5-one with phthalimidoaminoacids, followed by photolysis (in acetone at 300 nm) of the resulting 91.…”

Section: Oxazolesmentioning

confidence: 99%

Synthesis of Heteroaromatics via Rearrangement Reactions

Vivona

Buscemi

Pibiri

et al. 2009

Handbook of Synthetic Photochemistry

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The varied family of heteroaromatics contains a large fraction of organic compounds, many of which have found important applications in different fields. Many synthetic methodologies have been developed to obtain target systems and, among them, photochemical methods represent valid and elegant alternatives when the final targets are difficult to obtain through ground-state chemistry. In this chapter, we describe the photochemical synthesis of heteroaromatic compounds through rearrangement reactions, particularly via ring-transformations of heterocyclic precursors [1][2][3][4][5][6][7].A classification of all photoinduced heterocyclic ring-transformation reactions is quite difficult to achieve due to the large variety of mechanistic pathways, experimental conditions and affecting parameters. In some cases, the photochemical product and the starting substrate have the same heterocyclic nucleus. In this chapter, we will refer to such reactions, characterized by the identity of the starting and final ring, as ring-degenerate rearrangements.In general, photoinduced rearrangements of heterocycles leading to heteroaromatic compounds may involve ring-contraction, internal cyclization, ring-expansion, ring-opening or ring-closure, and ring-fragmentation processes. As for five-membered rings, two processes will be repeatedly quoted throughout this chapter:. The ring contraction-ring expansion route (RCRE), which explains the formal interchange between two adjacent ring-atoms. This results from the photoinduced cleavage of the weakest bond in the ring with formation of a three-membered ring intermediate. The latter is then converted, either thermally or photochemically, into the final five-membered heterocyclic product (see e.g., Scheme 12.22). . The internal cyclization-isomerization route (ICI), which involves the formation of a bicyclic species featuring a single bond between the ring-atoms in the 2-and 5-positions of the original heterocycle. Sigmatropic shifts then occur, leading to different bicyclic intermediates from which the final products will arise (see e.g., Scheme 12.2).Handbook of Synthetic Photochemistry. Edited

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Chemistry of 5-oxodihydroisoxazoles. Part 18.1 Synthesis of oxazoles by the photolysis and pyrolysis of 2-acyl-5-oxo-2,5-dihydroisoxazoles

Cited by 33 publications

References 36 publications

Synthesis of aromatic heterocycles

Synthesis of aromatic heterocycles

Synthesis of Substituted Oxazoles from N‐Acyl‐β‐hydroxyamino Acid Derivatives

Synthesis of Heteroaromatics via Rearrangement Reactions

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