SmI2-Mediated 3-exo-trig cyclisation of δ-oxo-α,β-unsaturated esters to cyclopropanols and derivatives
摘要:
In the presence of samarium diiodide and a proton source, delta-oxo-gamma,gamma-disubstituted-alpha,beta-unsaturated esters of general formula R-CO-C(R',R')-CH=CH-CO2Bn readily cyclise to trans-cyclopropanol products and/or lactones derived from the cis isomers. For R=aryl, good stereoselectivities (ca 90%) in favor of the alcohols are generally obtained while a mixture of alcohols and lactones is obtained with R=alkyl or H. For R=cyclopropyl, the lactone is exclusively obtained in more than 90% yield. A mechanistic rationalisation of these variations of diastereoselectivity is proposed. (C) 2004 Elsevier Ltd. All rights reserved.
Verfahren zur Herstellung von 1,1-Dihalogen-alkenen
申请人:BAYER AG
公开号:EP0035724A2
公开(公告)日:1981-09-16
Die Erfindung betrifft ein Verfahren zur Herstellung von 1,1-Dihalogen-alkenen, das dadurch gekennzeichnet ist, daß man Carbonylverbindungen mit Trihalogenacetaten in Gegenwart von angenähert der äquimolaren Menge eines Phosphorigsäuretrialkylesters (Trialkylphosphits) oder eines Phosphorigsäuretriamids und gegebenenfalls in Gegenwart eines Verdünnungsmittels bei Temperaturen zwischen 0 und 200°C umsetzt.
Die Erfindung betrifft ein Verfahren zur Herstellung von 1,1-Dichlor-alkenen, das dadurch gekennzeichnet ist, daß man Carbonylverbindungen mit Trichlormethanphosphonsäureestern in Gegenwart von wenigstens der äquimolaren Menge eines Phosphorigsäuretriamids umsetzt.
In the presence of samarium diiodide and a proton donor (tert-butanol or phenol), δ-oxo-γ,γ-disubstituted-alkylidenemalonates readily cyclise according to the 3-exo-trig mode to give, depending on the exact nature of the substrate, trans and cis cyclopropanols or lactones derived from the cis isomers. Total stereoselectivity towards the formation of trans cyclopropanols is observed with di-tert-butyl alkylidenemalonates when PhOH is used as the protonating agent.
In the presence of samarium diiodide and a proton source, delta-oxo-gamma,gamma-disubstituted-alpha,beta-unsaturated esters of general formula R-CO-C(R',R')-CH=CH-CO2Bn readily cyclise to trans-cyclopropanol products and/or lactones derived from the cis isomers. For R=aryl, good stereoselectivities (ca 90%) in favor of the alcohols are generally obtained while a mixture of alcohols and lactones is obtained with R=alkyl or H. For R=cyclopropyl, the lactone is exclusively obtained in more than 90% yield. A mechanistic rationalisation of these variations of diastereoselectivity is proposed. (C) 2004 Elsevier Ltd. All rights reserved.