Conformational rigidity of silicon- stereogenic silanes in asymmetric catalysis: A comparative study

• Sebastian Rendler and
• Martin Oestreich

Beilstein J. Org. Chem. 2007, 3, No. 9, doi:10.1186/1860-5397-3-9

• Sebastian Rendler Martin Oestreich Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, D-48149 Münster, Germany 10.1186/1860-5397-3-9 Abstract In recent years, cyclic silicon-stereogenic silanes were successfully employed as stereoinducers in transition

• metal-catalyzed asymmetric transformations as exemplified by (1) the hydrosilylation of alkenes constituting a chirality transfer from silicon to carbon and (2) the kinetic resolution of racemic mixtures of alcohols by dehydrogenative silicon-oxygen coupling. In this investigation, a cyclic and a

• structurally related acyclic silane with silicon-centered chirality were compared using the above-mentioned model reactions. The stereochemical outcome of these pairs of reactions was correlated with and rationalized by the current mechanistic pictures. An acyclic silicon-stereogenic silane is also capable of

Generation of pyridyl coordinated organosilicon cation pool by oxidative Si-Si bond dissociation

• Toshiki Nokami,
• Ryoji Soma,
• Yoshimasa Yamamoto,
• Toshiyuki Kamei,
• Kenichiro Itami and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2007, 3, No. 7, doi:10.1186/1860-5397-3-7

• C-S bond dissociation. Very recently, the oxidative C-C bond dissociation has been found to be effective for generation of a pool of a carbocation having a stabilizing group as shown in Scheme 1[6]. We have been interested in generation and accumulation of cations of other elements such as silicon

• on both silicon atoms were used as starting materials for electrochemical generation and accumulation of organosilicon cations, because oxidative dissociation of the Si-Si bond leads to the formation of two equivalents of organosilicon cations and no other product is formed. In our earlier study, it

• ]. The coordination also stabilizes the thus-generated radical cation and weakens the C-Sn bond. A similar effect of intramolecular coordination was observed in the case of silicon [23]. Another important point is that pyridyl group is rather inactive toward the anodic oxidation. Thus, we chose to use a

Tether- directed synthesis of highly substituted oxasilacycles via an intramolecular allylation employing allylsilanes

• Peter J. Jervis and
• Liam R. Cox

Beilstein J. Org. Chem. 2007, 3, No. 6, doi:10.1186/1860-5397-3-6

• if the silyl connection were contained within the allylsilane itself; third, the silyl tether remains intact post allylation, to provide a product that can be elaborated in a wide variety of ways. We recently showed that this Temporary Silicon Connection strategy provides a useful method for the

• amount of the corresponding side-product diene syn-13a and syn-13b (the diene may be formed in a variety of ways; we favour a mechanism involving a vinylogous silicon-mediated olefination as this best accounts for the excellent (E)-stereoselectivity observed). [25][26][27] The relative stereochemistry of

Reaction of benzoxasilocines with aromatic aldehydes: Synthesis of homopterocarpans

• Míriam Álvarez-Corral,
• Cristóbal López-Sánchez,
• Leticia Jiménez-González,
• Antonio Rosales,
• Manuel Muñoz-Dorado and
• Ignacio Rodríguez-García

Beilstein J. Org. Chem. 2007, 3, No. 5, doi:10.1186/1860-5397-3-5

• quantitatively (Scheme 3). The 1H NMR is very similar to that of the starting material, but for the methyl groups on silicon, which appear now as doublets due to their coupling with the 19F (3JH-F = 7.3 Hz). This coupling is also observed for the methylene on silicon H4', which exhibits now an additional

• splitting (3JH-F = 6.5 Hz) (for details see Supporting Information File 1). 13C NMR also reveals the presence of the fluorine on the silicon, because the signal due to the methyl groups appears as a doublet (2JC-F = 14.8 Hz) as well as the signal due to C4' (2JC-F = 13.5 Hz). 19F NMR shows only one signal

Contemporary organosilicon chemistry

• Steve Marsden

Beilstein J. Org. Chem. 2007, 3, No. 4, doi:10.1186/1860-5397-3-4

• longer established field of organoboron chemistry [2]. This expansion in activity reflects not only the sustained popularity of traditional silicon-based reactions and reagents, but also newer departures such as the effective application of organosilicon compounds in transition metal-catalysed cross

• Chemistry". We have contributions from some of the leading practitioners in the area, covering a wide range of topics including the stereoselective construction of oxygen and nitrogen-containing heterocycles, the use of tethered silicon reagents to deliver acyclic stereocontrol, chiral-at-silicon reagents

• fluorination, cyclopropane chemistry and the development of silicon-containing drug candidates should be available shortly. Be sure to check back to keep abreast of the latest developments as the Series grows. Steve Marsden Guest Editor

Synthesis of highly substituted allenylsilanes by alkylidenation of silylketenes

• Stephen P. Marsden and
• Pascal C. Ducept

Beilstein J. Org. Chem. 2005, 1, No. 5, doi:10.1186/1860-5397-1-5

• -carbon partners in [3+2] annulation reactions. Thus, reaction with aldehydes,[7] imines/iminiums,[7][8] enones [9][10][11] and nitrosyl cations [12] leads to dihydrofurans, dihydropyrroles, cyclopentenes and isoxazoles respectively.[13] In most cases the silicon is retained in the final product and can

• carboethoxy-stabilised phosphoranes 4 and 5. At the outset, it was by no means certain that these would react efficiently with substituted silylketenes 1 since it is well documented that nucleophiles attack silylketenes anti to the silicon, [29]ie the phosphoranes would be approaching from the same side as

• predominant products of reaction. It appears that the presence of the (hetero)aryl group labilises the silicon to cleavage under the reaction conditions, likely reflecting the silyl group acting as an electrofuge with the (hetero)aryl substituent stabilising incipient anionic character at the adjacent carbon