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Darstellung und Dehydratisierung von 2-(α-Alkyl)- oder (α-Aryl)-substituierten Hydroxymethyl-5-methoxy-1,3-benzoxathiol-3,3-dioxiden
Authors:Wilhelm Meichle  Hans-Hartwig Otto
Abstract:Synthesis and Water Elimination of 2-(α-Alkyl-) or (α-Aryl)-Substituted Hydroxymethyl-5-methoxy-1,3-benzoxathiol-3,3-dioxides The reaction of α,α-disilylated sulfones 1 with acetaldehyde in the presence of TBAF yields the aldols 2 and 3 together with small amounts of the dialdols 4 and the olefins 5/6 . From aromatic aldehydes the formation of olefins 9 is preferred. A reaction pathway is proposed. Acetylation of the unsilylated derivative 7 yields the 2-acetyl derivatives 12 which may be reduced by selectride. Depending on the conditions the formation either of 2 or of 3 is preferred. Water elimination from 2 and 3 with thionylchloride in pyridine stereoselectivly produces the olefines 5 or 6 , respectively. Intermediates are the halogen compounds 14 which are formed by inversion.
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