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  • Activation  (1)
  • Alkylidenation, intramolecular  (1)
  • Carbonyl compounds  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1125-1130 
    ISSN: 0009-2940
    Keywords: Indoles, 2-aryl- ; Titanium graphite ; Zindoxifene ; Tumor-growth inhibitors ; Alkylidenation, intramolecular ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Highly reactive titanium on graphite is used to reductively cyclize electron-rich acylamino carbonyl compounds 7, 8, 12, 14, and 16 to the corresponding indole derivatives 9, 10, 13, 15, and 17. Compound 9b is a known precursor of the mammary tumor-inhibiting compound zindoxifene (2). The other products are new analogues of this anticancer drug, exhibiting the substitution pattern previously recognized to be essential for high pharmacological activity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 32 (1993), S. 164-189 
    ISSN: 0570-0833
    Keywords: Metals ; Reactivity ; Activation ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Today, the synthetic chemist has a large repertoire of metal activation methods at his disposal. After a first breakthrough was made at the beginning of the seventies with the introduction of the Rieke metals, a series of further, in part more efficient methods were describes, based on which not only classical metal-induced reactions could be substantially improved but also completely new reactions could be discovered. In this article the individual activation methods are discussed and compared as far as is possible using the currently available data. Especially noteworthy are the metal-graphite combinations because of their unsurpassed reactivity and concomitant easy preparation and manipulation. As shown by numerous applications of these reagents on polyfunctional substrates, particularly natural products, high reactivity of the metal and excellent selectivity are by no means precluded. Besides the purely preparative aspects also insights gained so far into the general principles and limits of metal activation are outlined, and attempts at determining the morphology of highly dispersed systems are reported.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 35 (1996), S. 2442-2469 
    ISSN: 0570-0833
    Keywords: alkenes ; carbonyl compounds ; heterocycles ; McMurry reactions ; titanium compounds ; Alkenes ; Carbonyl compounds ; Heterocycles ; McMurry reaction ; Titanium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Among the applications of low-valent titanium in organic synthesis, the reductive coupling of carbonyl compounds to produce alkenes (the McMurry reaction) is particularly prominent. Discovered at the beginning of the 1970s, it has been developed and tested repeatedly, for example in numerous syntheses of natural products. This alkene synthesis has become a standard reaction in the repertoire of preparative chemists. However, the possibilities of low-valent titanium are by no means limited to this process: the last few years have brought some spectacular applications of the conventional McMurry reaction (for example the synthesis of taxol) along with a considerable extension of the scope of reductive carbonyl couplings. Thus, diverse heterocycles are now accessible following novel and efficient pathways based on intramolecular cross-coupling of functional groups - some of which were hitherto considered to be inert to titanium. The use of this method for the synthesis of indole and pyrrole alkaloids illustrates the new possibilities. At the same time, considerably simplified methods for conducting McMurrytype reactions have been developed. Examples include the particularly convenient “instant” method, the first ketone-amide coupling reactions requiring only catalytic amounts of titanium salts, and the first application of commercially available titanium powder as a coupling agent. Last but not least, the detailed investigation of diverse classical McMurry reagents has afforded a deeper understanding of the nature and mode of action of low-valent titanium. Revision of some of the current conceptions of the process of reductive carbonyl coupling is thus indispensable.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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