The Development of Enantioselective Rhodium-Catalysed Hydroboration of Olefins

Carroll, Anne-Marie; O’Sullivan, Timothy P.; Guiry, Patrick J.

doi:10.1002/adsc.200404232

Cited by 328 publications

(96 citation statements)

References 130 publications

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“…[1] Indeed, several reactions involving carbon-hydrogen, [2][3][4][5][6] carbon-carbon, [7][8][9][10] or carbon-heteroatom [11][12][13][14][15] bond formation provide highly asymmetric induction for various substrates, and some of them are applied on industrial scales for the production of substances with useful agrochemical, flavor, or pharmaceutical rhodium-substrate complex, has been proposed. This model offers an alternative to the quadrant rule, well adapted to the C 2 -symmetry ligands and the chair conformation of their complex derivatives.…”

Section: Introductionmentioning

confidence: 99%

Modular P‐Chirogenic Aminophosphane‐Phosphinite Ligands for Rh‐Catalyzed Asymmetric Hydrogenation: A New Model for Prediction of Enantioselectivity

Darcel

Moulin²,

Henry³

et al. 2007

Eur J Org Chem

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An original series of P-chirogenic aminophosphane-phosphinite (AMPP) ligands has been synthesized from (+)-or (-)-ephedrine in 23 to 61 % overall yields by a versatile threestep methodology. The AMPP ligands, bearing either one or two P-chirogenic centers, were used in the form of rhodium complexes for the catalyzed hydrogenation of α-acetamidocinnamate as a test reaction. Notably, even with AMPP ligands all derived from (+)-ephedrine, variation of the substituent on a P-center allowed the phenylalanine derivatives to be obtained in either (S) or (R) absolute configurations, with ee values ranging from 99 % (S) to 88% (R). The asymmetric induction was analyzed with the aid of X-ray structures of AMPP complexes, and a new model for the enantioselectivity, taking into consideration the boat conformation and the steric and electronic dissymmetries at the dihydride

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Section: Introductionmentioning

confidence: 99%

Modular P‐Chirogenic Aminophosphane‐Phosphinite Ligands for Rh‐Catalyzed Asymmetric Hydrogenation: A New Model for Prediction of Enantioselectivity

Darcel

Moulin²,

Henry³

et al. 2007

Eur J Org Chem

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“…Along with hydroboration, [1][2][3][4] transition-metalcatalyzed diboration [5] has become useful for the functionalization of unsaturated organic compounds. [6,7] This reaction is widely applicable to substrates such as alkynes [8,9] arynes, [10] alkenes, [11][12][13] carbenoids, [14,15] as well as diazo [16] and carbonyl compounds.…”

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confidence: 99%

Unexpected Generation of Diastereomers by Double Diboration of a Dialkyne

Bauer

Braunschweig

Gruß

et al. 2011

Chemistry A European J

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During the last two decades, boron compounds have become established as versatile reagents in organic synthesis, and different methods have been developed for their preparation. Along with hydroboration, [1][2][3][4] transition-metalcatalyzed diboration [5] has become useful for the functionalization of unsaturated organic compounds. [6,7] This reaction is widely applicable to substrates such as alkynes [8,9] arynes, [10] alkenes, [11][12][13] carbenoids, [14,15] as well as diazo [16] and carbonyl compounds. [17][18][19][20] Although bis(catecholato)diborane(4) and bis(pinacolato)diborane(4) represent by far the most commonly employed diborane(4) species, the reaction is not restricted to their use. For instance, several diboranes(4) with interesting properties are derived from [2]borametalloarenophanes. The first example of this class of organometallic compound, the [2]boraferrocenophane 1, was prepared by Herberhold, Wrackmeyer and co-worker, [21] while the molecular structure along with an alternative synthesis was published by our group.[22] Subsequently, a series of [2]borametalloarenophanes has appeared. [23-28b] These ansa complexes show tilted molecular structures, thus featuring significant molecular strain. In 2006, we successfully exploited this ring strain in oxidative addition reactions of [2]borametalloarenophanes to low-valent platinum centers, affording[3]diboraplatinametalloarenophanes. In addition, we demonstrated the suitability of [2]borametalloarenophanes as diboranes(4) in the platinum-mediated diboration of alkynes to form [4]diboradicarbametalloarenophanes.[29] By expansion of this strategy, we also achieved the diboration of diazo compounds [16] and isocyanides.[30]Herein, we report on the two diastereomeric [4]diboradicarbaferrocenophanes 4 and 5, which were obtained by double diboration of the conjugated dialkyne 3 either by a platinum-mediated route employing the [2]boraferrocenophane 1 in the presence of [PtA C H T U N G T R E N N U N G (PEt 3 ) 3 ], or stoichiometrically by using the [3]diboraplatinaferrocenophane 2, directly (Scheme 1). In contrast to related transformations of monoalkynes, [29] monitoring the reaction progress by multinuclear NMR spectroscopy revealed the gradual disappearance of the starting materials, and the formation of two distinct compounds in benzene solution at elevated temperatures. Both species feature similar resonances in the 1 H, 11 B, and 13 C NMR spectra, which we rationalized by the generation of diastereomeric species. Complexes 4 and 5 were eventually isolated after workup as orange, moderately moisture-sensitive powders. The NMR spectroscopic data of both diastereomers are fully consistent with the presence of doubly bis(borylated), conjugated triene systems bearing two ferro-

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“…RhCl(PPh 3 ) 3 . Since this remarkable discovery, a considerable amount of research has focussed on investigating the mechanism and scope of catalyzed hydroboration reactions [6,[10][11][12][13]. Much less studied, however, is the use of alternate borane sources [14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 98%