Nickel(0)-Catalyzed Enantio- and Diastereoselective Synthesis of Benzoxasiloles: Ligand-Controlled Switching from Inter- to Intramolecular Aryl-Transfer Process
摘要:
A highly enantioselective synthesis of 3-aryl-, vinyl-, and alkynyl-2,1-benzoxasiloles (up to 99.9% ee and 99% yield) was achieved via the sequential activation of an aldehyde and a silane by nickel(0). This strategy was applied to a simultaneous generation of carbon- and silicon-stereogenic centers with excellent selectivity (dr = 99:1) via diastereotopic aryl transfer. Initial mechanistic studies revealed the complete switching of an aryl-transfer process from an intermolecular (racemic synthesis in the presence of IPr) to an intramolecular (enantioselective synthesis using chiral NHC, L5) fashion. A plausible rationale for the switching of the aryl-transfer process is given by a preliminary DFT calculation, which suggests that the coordination of 1 to the nickel(0)/L5 fragment in an eta(2)-arene:eta(2)-aldehyde fashion would be a key to the intramolecular process, while the formation of the corresponding intermediate is not possible in the presence of IPr. Owing to the chemically labile nature of its C-Si and O-Si bonds, enantioenriched benzoxasiloles are utilized for the synthesis of chiral building blocks and antihistaminic and anticholinergic drug molecules such as (R)-orphenadrine and (S)-neobenodine with no erosion of the enantiomeric excess.
The present invention relates to fungicidal N-cycloalkyl-N-[(trisubstitutedsilylphenyl)methylene]carboxamide derivatives and their thiocarbonyl derivatives, their process of preparation and intermediate compounds for their preparation, their use as fungicides, particularly in the form of fungicidal compositions and methods for the control of phytopathogenic fungi of plants using these compounds or their compositions.
[EN] N-CYCLOALKYL-N-[(TRISUBSTITUTEDSILYLPHENYL)METHYLENE]-(THIO)CARBOXAMIDE DERIVATIVES<br/>[FR] DÉRIVÉS DE N-CYCLOALKYL-N-[(SILYLPHÉNYLE TRISUBSTITUÉ) MÉTHYLÈNE]-(THIO)CARBOXAMIDE
申请人:BAYER CROPSCIENCE AG
公开号:WO2013156560A1
公开(公告)日:2013-10-24
The present invention relates to fungicidal N-cycloalkyl-N-[(trisubstitutedsilylphenyl)methylene] carboxamide derivatives and their thiocarbonyl derivatives, their process of preparation and intermediate compounds for their preparation, their use as fungicides, particularly in the form of fungicidal compositions and methods for the control of phytopathogenic fungi of plants using these compounds or their compositions.
Highly Efficient Activation of Organosilanes with η<sup>2</sup>-Aldehyde Nickel Complexes: Key for Catalytic Syntheses of Aryl-, Vinyl-, and Alkynyl-Benzoxasiloles
An eta(2)-aldehyde nickel complex was utilized as an effective activator for an organosilane in order to generate a hypervalent silicate reactant for the first time. This method was successfully applied to the highly efficient syntheses of 3-aryl-, vinyl-, and alkynyl-2,1-benzoxasiloles from benzaldehydes with aryl-, vinyl-, and alkynylsilyl groups at the ortho position. Initial mechanistic studies revealed that an intermolecular aryl transfer process was involved in the reaction mechanism. The formation of an eta(2)-aldehyde complex was directly confirmed by NMR.
Et-duphos-nickel-catalyzed asymmetric arylation of benzaldehyde derivatives bearing an ortho-Me2PhSi group with potassium aryltriolborates
作者:Fumie Sakurai、Kazuhiro Kondo、Toyohiko Aoyama
DOI:10.1016/j.tetlet.2009.08.019
日期:2009.11
The Ni-catalyzed asymmetric arylation of benzaldehydes bearing an ortho-masked H group with potassium aryltriolborates has been developed. The keys to success were (i) steric tuning of benzaldehyde derivatives with an ortho-Me2PhSi group, and (ii) the use of potassium aryltriolborates as aryl sources. (C) 2009 Elsevier Ltd. All rights reserved.