Addition of Xanthenyl and Thioxanthenyl Halides to Asymmetric Diarylethylenes and Their 2‐Halogeno‐Derivatives

Tadros, Wadie; Sakla, Alfy Badie; Awad, Sami Bassili; Abdul-Malik, Nadia Fouad

doi:10.1002/hlca.19730560602

Cited by 5 publications

(1 citation statement)

References 19 publications

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“…We were also intrigued by the possibility of applying the rigid xanthene scaffold in enantioselective hydride abstraction after installation of a chiral appendage. The carbenium ion precursor 9-bromoxanthene ( 6 ) was synthesized from 9-xanthenol by treatment with HBr …”

Section: Resultsmentioning

confidence: 99%

Hydride Abstraction from η³-Allylic Molybdenum Complexes Exploring Various Diaryl Carbenium Ion Precursors. A Study toward Enantioselective Hydride Abstraction

2002

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Section: Resultsmentioning

confidence: 99%

Hydride Abstraction from η³-Allylic Molybdenum Complexes Exploring Various Diaryl Carbenium Ion Precursors. A Study toward Enantioselective Hydride Abstraction

2002

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ChemInform Abstract: ADDITION OF XANTHENYL AND THIOXANTHENYL HALIDES TO ASYMMETRIC DIARYLETHYLENES AND THEIR 2‐HALOGENO‐DERIVATIVES

Tadros

Sakla

Awad

et al. 1973

Chemischer Informationsdienst

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Halogenation of Xanthenyl and Thioxanthenylallenes

Abdul-Malik

Awad

Sakla

1979

Helvetica Chimica Acta

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Reactions of acids with vinylidenexanthenes (or thioxanthenes) 1 and 9methoxy-9-vinylxanthenes (or thioxanthenes) 8 give xanthene-(or thioxanthene-) 9-spiro-1 '-indenes 7. With bromine or sulfuryl chloride they give the corresponding 2'-halogenoxanthene-(or thioxanthene-)9-~piro-1 '-indenes 5. Formation of such derivatives depends on preferential attack of the reagents on allenes 1 to give initially xanthylium (or thioxanthylium) ions 3 which cyclize. One 71 bond of the allenes 1 can be selectively reduced in acid media. Chemical and spectral evidence for these routes are presented.Recently we reported on the cyclization of vinylidenexanthenes (1, Y = 0, R = alkoxy) in acid media which give xanthene-9-spiro-1'-indenes (7, Y = 0) [l]. This cyclization revealed the preferential reactivity of the 71 bond of the involved xanthene residue. We have subsequently investigated reactions of equimolecular quantities of either bromine or sulfuryl chloride with vinylidenexanthenes and thioxanthenes (1, Y = 0 or S, R = alkoxy) in order to have further insight on the behaviour and reactivity of such polyarylallenes towards halogenation.Addition of bromine took place readily with instantaneous development of very deep blue-violet colour instead of the normal discharge of bromine colour. The same colour developed on addition of sulfuryl chloride to 1 ( Y = O or S) in carbon tetrachloride solution. This suggested that heteroatom in this type of compound would be responsible for development of such colour [l] as it may encourage migration of one halogen atom due to concerted electron-shift in 2 with formation of the coloured oxonium derivative 3. On the other hand, addition may take place through an initial cation attack on the activated central carbon atom of 1, rather than free radical addition to give 3 (Y = 0 or S). On heating solutions of 3 (Y = 0 or S, R = alkoxy) ready evolution of hydrogein halide occurred, affording mainly the corresponding 2'-bromo-6'-alkoxy-3'-aryl-xanthene-(or thioxanthene-)9-spiro-1 '-indenes 5 (Y = 0 or S, X = Br, R = alkoxy). When bromine was added to 1 (Y = 0, R = OMe) and the reaction mixture was left 2 h at RT., the deep blue-violet crystals isolated were identified as the tribromide: 4 (Y = 0, X = Br, R = OMe), in addition to the corresponding bromoindene 5. Compound 4 could be formed by addition of some liberated hydrogen bromide to 3. Formation of bro-Oo18-019)3/79/6/ 1872-06$0l.Oo/O 0 1979 Schweizerische Chemische Gesellschaft

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Addition of Xanthenyl and Thioxanthenyl Halides to Asymmetric Diarylethylenes and Their 2‐Halogeno‐Derivatives

Cited by 5 publications

References 19 publications

Hydride Abstraction from η³-Allylic Molybdenum Complexes Exploring Various Diaryl Carbenium Ion Precursors. A Study toward Enantioselective Hydride Abstraction

Hydride Abstraction from η³-Allylic Molybdenum Complexes Exploring Various Diaryl Carbenium Ion Precursors. A Study toward Enantioselective Hydride Abstraction

ChemInform Abstract: ADDITION OF XANTHENYL AND THIOXANTHENYL HALIDES TO ASYMMETRIC DIARYLETHYLENES AND THEIR 2‐HALOGENO‐DERIVATIVES

Halogenation of Xanthenyl and Thioxanthenylallenes

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Addition of Xanthenyl and Thioxanthenyl Halides to Asymmetric Diarylethylenes and Their 2‐Halogeno‐Derivatives

Cited by 5 publications

References 19 publications

Hydride Abstraction from η3-Allylic Molybdenum Complexes Exploring Various Diaryl Carbenium Ion Precursors. A Study toward Enantioselective Hydride Abstraction

Hydride Abstraction from η3-Allylic Molybdenum Complexes Exploring Various Diaryl Carbenium Ion Precursors. A Study toward Enantioselective Hydride Abstraction

ChemInform Abstract: ADDITION OF XANTHENYL AND THIOXANTHENYL HALIDES TO ASYMMETRIC DIARYLETHYLENES AND THEIR 2‐HALOGENO‐DERIVATIVES

Halogenation of Xanthenyl and Thioxanthenylallenes

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Hydride Abstraction from η³-Allylic Molybdenum Complexes Exploring Various Diaryl Carbenium Ion Precursors. A Study toward Enantioselective Hydride Abstraction

Hydride Abstraction from η³-Allylic Molybdenum Complexes Exploring Various Diaryl Carbenium Ion Precursors. A Study toward Enantioselective Hydride Abstraction