Fe3+-Catalyzed transacetalization of 2-alkoxytetrahydrofurans with alcohols
摘要:
The transacetalization of 2-alkoxy-4-benzylidenctetraiiydrofurans with alcohols proceeds smoothly with the aid of Fe(ClO4)(3) catalyst. The catalyst reactivity is ordered as Fe(ClO4)(3)>Zn(ClO4)2>Mg(ClO4)(2). The present transacetalization provides an entry for various 2-alkoxytetrahydrofurans, which have potential as anticancer agents. (C) 2007 Elsevier Ltd. All rights reserved.
Palladium(II)-Catalyzed Oxidative Transformation of Allylic Alcohols and Vinyl Ethers into 2-Alkoxytetrahydrofurans: Catechol as an Activator of Catalyst
[chemical reaction: see text]. A highly effective synthesis of 2-alkoxytetrahydrofurans from allylic alcohols and vinyl ethers was achieved by using catalytic amounts of Pd(OAc)2, Cu(OAc)2, and catechol (1:1:2) under O2. The use of catechol as an activator of Pd(II)-Cu(II) catalyst has been unprecedented. The 2-alkoxytetrahydrofurans are formed via oxypalladation of allylic alcohols toward vinyl ethers
[GRAPHICS]The use of PdX2, CuX2 (X = OAc, OCOCF3, or Cl), and catechol together with (S,S)-4,4'-bisbenzyl-2,2'-bioxazoline under O-2 induces the asymmetric coupling of cinnamyl alcohols and vinyl ethers to give (R)-(+)-2-alkoxy-4-benzylidenetetrahydrofurans in 40-53% ee (79% yield). The present study provides implications for the so-called Wacker catalyst of PdX2 and CuX2, in terms of that the anionic ligands (X) of Pd and Cu interchange between two metals.
Palladium(II)-Catalyzed Synthesis of 2-Alkoxytetrahydrofurans from Allylic Alcohols and Vinyl Ethers: Stereospecificity and Catalysis
The reaction of (E)- or (Z)-cinnamyl alcohol and ethyl vinylether with a catalyst consisting of Pd(OAc) 2 , Cu(OAc) 2 , and catechol (1:1:2) under O 2 gives a good yield of(Z)- or (E)-4-benzylidene-2-ethoxytetrahydrofuran, respectively. Similarly, 2-butoxy-4-exomethylenetetrahydrofuran was obtained from allyl alcohol and butyl vinylether. In the case of allyl alcohol, however, the catalysis does
The transacetalization of 2-alkoxy-4-benzylidenctetraiiydrofurans with alcohols proceeds smoothly with the aid of Fe(ClO4)(3) catalyst. The catalyst reactivity is ordered as Fe(ClO4)(3)>Zn(ClO4)2>Mg(ClO4)(2). The present transacetalization provides an entry for various 2-alkoxytetrahydrofurans, which have potential as anticancer agents. (C) 2007 Elsevier Ltd. All rights reserved.