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  • 1
    ISSN: 0947-3440
    Keywords: Amino alcohols ; Bicyclic pyrrolidine and piperidine derivatives ; Diastereoselective ring expansion ; Chiral auxiliaries ; Waste prevention ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New, chiral bicyclic 3-hydroxypiperidines (4S)-2a-e are synthesized from the β-amino alcohols (3R)-1a-e. In an one-step reaction (4S)-2a-e are obtained by a high diastereoselective ring expansion (dr ≥ 95:5). As well, the amino alcohol (3S)-1a leads to the corresponding rearranged epimer bicyclic piperidine derivative (4R)-2a (dr ≥ 95:5). Thus, it is possible to clarify the influence of the three stereogenic centers of the parent compound regarding the diastereoselectivity of the ring expansion. After oxidation of the tert-amino sec-alcohol (4S)-2a to the corresponding α-amino ketone 4, new 3-hydroxypiperidines (4Ξ)-5a, b12 and (4RS)-6 are obtained by a diastereoselective Grignard addition. Furthermore, the achiral and the chiral reduction of 4 to the β-amino alcohols (4S)-2a and (4R)-2a is described. These are further examples of the utilization of industrial waste material (all-R)-2-azabicyclo[3.3.0]octane-3-carboxylic acid (all-R)-3.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-2313
    Keywords: Aluminium ; indium ; Al—Al bond ; In—In bond ; benzoato bridges ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Reactions of R2Al—AlR2 and R2In—InR2 with Benzoic Acid - Synthesis and Crystal Structure of R2Al(μ-H)(μ-O2C—C6H5)AlR2 and RIn(μ-O2C—C6H5)4InR [R = CH(SiMe3)2]Tetrakis[bis(trimethylsilyl)methyl]dialane(4) 1 reacts with benzoic acid by the oxidative cleavage of the Al—Al bond: The Al atoms are inserted into the O—H bond of the acid and the proton is reduced to a hydride anion. As shown by a crystal structure determination, the product 4 shown an unprecedented structure with both dialkylaluminium fragments unsymmetrically bridged by the hydrogen atom and a benzoato group. 4 can be described as a model compound for the first step of the hydrolysis of compounds with low-valent Al atoms as well as elemental aluminium itself. The diindane(4) analogue of 1 (2) and benzoic acid yield, however, elemental indium and mixed alkyl benzoato indium derivatives, from which bis(trimethylsilyl)methyldi(benzoato)indium 9 has been characterized by a crystal structure determination. 9 consists of a dimer with a remarkable cage structure, in which both monoalkylindium groups are interconnected by four benzoato-O,O′ bridges.
    Notes: Tetrakis[bis(trimethylsilyl)methyl]dialan(4) 1 reagiert mit Benzoesäure unter oxidativer Öffnung der Al—Al-Bindung, wobei sich formal die Al-Atome in die O—H-Bindung der Säure einschieben und das Proton zu einem Hydridion reduzieren. Die beiden Dialkylaluminium-Fragmente des daraus erhaltenen Produkts 4 werden, wie durch Kristallstrukturbestimmung gezeigt wird, in bisher unbekannter Weise durch das Wasserstoffatom und eine Benzoatogruppe unsymmetrisch miteinander verbrückt. 4 läßt sich als Modellverbindung für die erste Stufe der Hydrolyse von Derivaten mit niederwertigen Al-Atomen und elementarem Aluminium beschreiben. Das zu 1 analoge Diindan(4) 2 ergibt dagegen mit Benzoesäuren unter Abscheidung von elementarem Indium gemischte Alkyl-benzoatoindium-Verbindungen. Bis(trimethylsilyl)methyl-di(benzoato)indium 9 wird kristallstrukturanalytisch untersucht; es liegt als Dimeres mit einer Käfigstruktur vor, in der zwei Monoalkylindium-Reste über vier Benzoato-O,O′-Brücken miteinander verbunden werden.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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