Halogenation of Heterocycles: I. Five-Membered Rings

Grimmett, M. R.

doi:10.1016/s0065-2725(08)60890-9

Cited by 34 publications

(11 citation statements)

References 701 publications

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“…18 Pyrazoles can also be made on a smaller scale by 1,3-dipolar cycloaddition of alkynes or related compounds to diazomethyl reagents (not shown in Scheme 2). 19 Once prepared, N-H pyrazoles can often be halogenated at the C4-position, 20 but other electrophiles may add to a nitrogen atom rather than, or as well as, to C4. 21 Suitably protected 4-iodopyrazoles can be good reagents for palladium-catalysed cross-coupling reactions.…”

Section: Syntheses and Physical Properties Of Pyrazolesmentioning

confidence: 99%

Pyrazoles and pyrazolides—flexible synthons in self-assembly

2009

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This Perspective summarises the chemistry of the pyrazole ring, and reviews the metal coordination modes adopted by 1H-pyrazoles and their anions. Pyrazolide anions are probably the most versatile ligands in coordination chemistry, with 20 different terminal or bridging coordination modes having been identified so far. Metal cluster compounds supported by pyrazolido ligation are surveyed, concentrating on those reported during the past ten years. Highlights include the wide structural diversity in apparently simple main group pyrazolides; luminescence and charge-transfer complexes in coinage metal pyrazolide clusters; the use of robust metal pyrazolide clusters to construct liquid crystals, supramolecular materials and metal-organic frameworks; and supramolecular complexes formed by pyrazolide-supported metallacrowns.

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Section: Syntheses and Physical Properties Of Pyrazolesmentioning

confidence: 99%

Pyrazoles and pyrazolides—flexible synthons in self-assembly

2009

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“…NMR study and tautomerim of pyrazolinones l H NMR data of pyrazolinones 1-13 are reported in Table 5. 4,4-Dihalogeno derivatives [8][9][10][11][12][13] can only exist as 2-pyrazolind-ones (tautomer a) if one does not consider nonaromatic pyrazoles, such as 4,4-dihalogeno-5-hydroxyisopyrazoles. In D M s 0 -d~ pyrazolinones 1-7 exist probably as 3pyrazolin-5-ones c. Actually, the only conclusive result is that tautomer a is not present at the limit of detection of H NMR (about 2-3%); tautomers b and c could be present in any relative proportion since their rate of interconversion is usually high in the NMR time scale.…”

Section: Origin Of Compoundmentioning

confidence: 99%

“…Only new compounds are reported in Table 1. (11) 190 (100) 3-(1-Adamantyl)pyrazolinone 2. To a solution of 1 g (4 mmol) of ethyl 3-(l-adamantyl)-3oxopropionate in water (5 mL) were added 0.27 g of hydrazine hydrochloride (4 mmol).…”

Section: Introductionmentioning

confidence: 99%

ChemInform Abstract: Studies in the Azole Series. Part 103. Adamantyl and Halogeno Pyrazolin‐5‐ones.

Cabildo¹,

Claramunt²,

Elguero³

et al. 1994

ChemInform

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“…Synthetic procedures for the preparation of fluorinated heterocycles include substitution of diazo groups (BalzSchiemann reaction) or chlorine (halogen exchange) by fluorine or cyclisation strategies involving acyclic fluorinated 'building blocks' [1,2,[4][5][6]. However, synthesis of the necessary functionalised precursors can sometimes be very complex and time consuming and, therefore, a more convenient approach to the synthesis of fluorinated heteroaromatic derivatives is, potentially, the selective transformation of carbon-hydrogen bonds to carbonfluorine bonds in reactions involving electrophilic fluorinating agents.…”

Section: Introductionmentioning

confidence: 99%