Diels–Alder reactions of trifluoromethyl alkenes with 5-ethoxyoxazoles: synthesis of trifluoromethylated pyridine derivatives

Sandford, Graham; Wilson, Ian D.; Timperley, Christopher M.

doi:10.1016/j.jfluchem.2004.04.013

Cited by 16 publications

(6 citation statements)

References 19 publications

(24 reference statements)

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“…Reaction of other CF 3 ‐alkenes 322b – d proceeded in similar way giving compounds 329 , 331 (as a result of decarboxylation from intermediate 330 ) and 334 (as a result of PhSO 2 H elimination), respectively, as major products (Scheme ) …”

Section: Fluorine‐containing Dienophilesmentioning

confidence: 96%

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Diels–Alder Reaction in the Synthesis of Fluorinated (Hetero)Aromatic Compounds

2018

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Numerous fluorinated (hetero)aromatic compounds have been synthesized by using the Diels–Alder reaction of fluorinated dienes/dienophiles with subsequent aromatization of the initially formed [4+2]‐cycloaddition products by various methods. This microreview presents diverse applications of the approach starting from the first examples in the 1960s up to recent advanced applications to illustrate the high potential of the method for the introduction of fluorine/polyfluoroalkyl substituents into (hetero)aromatic molecules.

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Section: Fluorine‐containing Dienophilesmentioning

confidence: 96%

“…Sandford et al proposed an interesting approach to per‐substituted pyridines by hetero‐Diels–Alder reaction of several electron‐poor CF 3 ‐alkenes 322 with oxazoles 323a , b (Scheme ) . Thus, the reaction of 322a with oxazoles 323a , b proceeded through intermediate 324 and ring opening to hemiacetal 325 .…”

Section: Fluorine‐containing Dienophilesmentioning

confidence: 99%

Diels–Alder Reaction in the Synthesis of Fluorinated (Hetero)Aromatic Compounds

2018

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“…Thus, in reaction with nitroethylene the oxazole 7 forms the nitropyrrole 10 instead of the expected nitropyridine [7] probably on account of the simultaneous cleavage of two bonds (C=N and C-O) in the cyclic adduct 8 followed by cyclization of the amino diketone 9. The pyrrole 12 is formed in an entirely similar way from the oxazole 11 [8]. In this case, however, the yield of the pyrrole is low, and the main product is the expected pyridine.…”

mentioning

confidence: 87%

Pyrroles from oxazoles

Бабаев

2012

Chem Heterocycl Comp

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The review is devoted to the transformation of oxazoles (including those with cationoid and mesoionic structures) into compounds of the pyrrole series.The search for new methods for the synthesis of heterocyclic systems is always actual, and the development of new methods for the construction of the pyrrole ring is particularly significant: the pyrrole ring is the basis of life on Earth, as it is the major subunit of the vitally important biomolecules hemoglobin and chlorophyll. Like any other heterocycle, the pyrrole ring can either be assembled from acyclic precursors (one or several synthons) or another heterocycle can be used as its precursor, i.e., the pyrrole can be obtained by recyclization. Transformation of the oxazole ring can provide an interesting and unusual method for the production of pyrrole. Oxazoles are widely used as starting compounds in synthesis (e.g., of pyridines, imidazoles, and other heterocycles), but the diversity of the methods used for the transformation of oxazoles into pyrroles has not yet been duly reflected in the review literature.Preparation of this review was prompted by the discovery by author and his group of an entirely new family of oxazole transformations to pyrroles in a series of condensed heterocycles containing a bridging nitrogen atom. This transformation, which has already been included in the latest edition of the classic textbook [1] and in a recent monograph on the chemistry of oxazoles [2], deserves comparison with all other examples (both known and exotic) of the oxazole conversion to pyrroles. Such a comparison, with the emphasis on the structural type of the transformation and on comparison of monocycles with condensed systems, is the theme of the present review, which is of interest both to synthesis specialists and to a wide range of teachers and high school students.It is not necessary to duplicate the known examples of the pyrrole synthesis from oxazoles (presented in the books [2,3] in the form of detailed tables), and they will only be used in the general schemes in order to complete the picture. In view of classification it is convenient to divide the oxazoles from which pyrroles can be obtained into simple subfamilies -neutral oxazoles (mesoionic and "normal") and oxazolium salts. PYRROLES FROM "NORMAL" OXAZOLES WITH NEUTRAL STRUCTUREDuring Vilsmeier formylation of the oxazole 1 the pyrrole 2 was isolated [4].

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“…In the suggested mechanism, intermediate 40 undergoes a release of CO 2 with concomitant aromatization to furnish compound 42 (Scheme , b). This reaction pathway circumvents the usual keto–enol isomerization process that provides 41 (Scheme , a) …”

Section: Hetero‐diels–alder (H‐d‐a) Reactions – Access To 3‐hydroxmentioning

confidence: 99%

5‐Alkoxyoxazole – A Versatile Building Block in (Bio)organic Synthesis

et al. 2016

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The 5‐alkoxyoxazole ring system has proved to be a useful and versatile building block that is involved in a variety of chemical transformations (e.g., hetero‐Diels–Alder reactions, formal 1,3‐dipolar cycloadditions, photochemical [2+2] cycloadditions, Claisen rearrangements, and ring‐opening processes). 5‐Alkoxyoxazoles have provided synthetic access to heteroaromatic scaffolds such as pyridines, furans, oxadiazolines, pyrrolidines, and significant linear chemical patterns, including amino acid derivatives. This review focuses on the broad range of reactivity of 5‐alkoxyoxazoles and their subsequent applications to the syntheses of naturally occurring compounds and biologically active molecules.

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Diels–Alder reactions of trifluoromethyl alkenes with 5-ethoxyoxazoles: synthesis of trifluoromethylated pyridine derivatives

Cited by 16 publications

References 19 publications

Diels–Alder Reaction in the Synthesis of Fluorinated (Hetero)Aromatic Compounds

Diels–Alder Reaction in the Synthesis of Fluorinated (Hetero)Aromatic Compounds

Pyrroles from oxazoles

5‐Alkoxyoxazole – A Versatile Building Block in (Bio)organic Synthesis

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