Heterofunctionalization

Catalytic Heterofunctionalization, A. Togni, H. Grtitzmacher 171 Copyright 2001 Wiley-VCH Verlag GmbH ISBNs 3-527-30234-4 (Hardcover) 3-527-60015-9 (Electronic)... 

The fourth chapter gives a comprehensive review about catalyzed hydroamina-tions of carbon carbon multiple bond systems from the beginning of this century to the state-of-the-art today. As was mentioned above, the direct - and whenever possible stereoselective - addition of amines to unsaturated hydrocarbons is one of the shortest routes to produce (chiral) amines. Provided that a catalyst of sufficient activity and stabihty can be found, this heterofunctionalization reaction could compete with classical substitution chemistry and is of high industrial interest. As the authors J. J. Bmnet and D. Neibecker show in their contribution, almost any transition metal salt has been subjected to this reaction and numerous reaction conditions were tested. However, although considerable progress has been made and enantios-electivites of 95% could be reached, all catalytic systems known to date suffer from low activity (TOP < 500 h ) or/and low stability. The most effective systems are represented by some iridium phosphine or cyclopentadienyl samarium complexes. 

For some of the reactions described in this book, rather precise and detailed ideas about the reaction mechanism exist. However, for many catalytic reactions, the mechanistic understanding is very poor and further experimental studies are certainly needed. Calculations proved to be a highly valuable tool to gain a more precise picture of the reaction pathways. However, mostly only model systems can be studied due to the complexity of the problem. Anyway, it is the firm believe of the authors that for any reaction with an activation barrier a suitable catalyst can be found. This book shall give an insight into what has been achieved in this area concerning the synthesis of heterofunctionalized organic molecules. It is the hope of all contributors that future retro-synthetic schemes will include the catalytic approaches outlined in this book. 

Miyaura, N. Hydroboration, Diboration, Silylboration and Stannylboration. In Catalytic Heterofunctionalization-, Togni, A., Griitzmacher, H., Eds. Wiley-VCH Weinheim 2001 pp 1-47. 

Abstract Aldehydes obtained from olefins under hydroformylation conditions can be converted to more complex reaction products in one-pot reaction sequences. These involve heterofunctionalization of aldehydes to form acetals, aminals, imines and enamines, including reduction products of the latter in an overall hydroaminomethylation. Furthermore, numerous conversions of oxo aldehydes with additional C.C-bond formation are conceivable such as aldol reactions, allylations, carbonyl olefinations, ene reactions and electrophilic aromatic substitutions, including Fischer indole syntheses. 

In related work, Sasai developed several bifunctional BINOL-derived catalysts for the aza-Morita-Baylis-Hillman (aza-MBH) reaction [111]. In early studies, careful optimization of the catalyst structure regarding the location of the Lewis base unit revealed 41 as an optimal catalyst for the aza-MBH reaction between acyclic a,P-unsaturated ketones and N-tosyl imines. Systematic protection or modification of each basic and acidic moiety of 41 revealed that all four heterofunctionalities were necessary to maintain both chemical and optical yields. As seen in Scheme 5.58, MO calculations suggest that one hydroxyl groups forms a... 

Miyaura, N. (A. Togni, H. Griitzmacher, Eds.) Catalytic Heterofunctionalization, Wiley-VCH, Chichester, 2001. Chapter 1. 

In this work, the chemistry of rhenium and technetium complexes anchored by heterofunctionalized phosphines and by scorpionates will be reviewed. Special attention will be given to those chemical aspects that, according to the authors, could enhance the ability of using these ligands in the development of target-specific radiopharmaceuticals. In this context, the chemistry of the novel fac-[M(CO)3]+ and [M(N)PXP]2+ metal fragments will also be mentioned,but to such an extent that minimizes any overlap with other reviews published in this special issue of Topics in Current Chemistry. 

Scheme 12 Complexes with heterofunctionalized phosphine ligands...

The characterization of compounds 48-54 in the solid state or in solution by multinuclear NMR spectroscopy confirmed the coordination mode of the phosphines. In complexes 51-54 the tridentate heterofunctionalized phosphines display a meridional coordination mode, with the remaining coordination sites being occupied by the oxo group and by other bidentate or mono-dentate coligands [56-58]. 

Scheme 22 Tricarbonyl complexes anchored by heterofunctionalized phosphines...

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