Access to 2-alkyl chromanones via a conjugate addition approach
摘要:
The introduction of alkyl substituents at C-2 of chromanones via conjugate addition of silyl enol ethers to a variety of chromenones is reported. In most cases racemic 2-alkyl chromanones were obtained in good yield in the presence of TMSOTf. The copper(II)-promoted conjugate addition of silyl enol ethers to chromenones was also carried out, albeit in low yields and no selectivity. Reliable syntheses of the chromenones via acylation of the corresponding beta-diketo-compounds are also described. (C) 2012 Elsevier Ltd. All rights reserved.
4-t-Butyldimethylsiloxy-l-benzopyrylium salt () was prepared in situ from chromone () and t-butyldimethylsilyl trillate and the salt reacted with enol silyl ethers, ketene silyl acetals and active methylene compounds to afford 2-substituted 4-t-butyldimethylsiloxy-2H-1-benzopyrans () in high yield. These products reacted with acid chlorides and an iminium salt to give 2,3-disubstituted 2,3-dihydro-
Heterodiene cycloadditions: Preparation and transformations of some substituted pyrano[4,3-b][1]benzopyrans
作者:Simon J. Coutts、Timothy W. Wallace
DOI:10.1016/s0040-4020(01)85668-4
日期:1994.1
Heterodienecycloadditions of 4-oxo-4H-1-benzopyrans with formyl, acetyl, or carboxyl substituents at C-3 to 1-alkoxy- or 1,1-dialkoxyalkenes produce 3-alkoxy- or 3,3-dialkoxy-4,4a- dihydropyrano[4,3-b][1]benzopyran-10-ones which are capable of a variety of selective transformations, including acid-induced epimerisation and/or retro-cycloaddition, reduction, hydrolysis and alcoholysis, in some cases
4-氧代-4 H -1-苯并吡喃在C-3处具有甲酰基,乙酰基或羧基取代基的异二烯环加成反应会生成3-烷氧基-或3,3-二烷氧基-4, 4a-二氢吡喃并[4,3- b ] [1]苯并吡喃-10-酮,在某些情况下,能够在多种条件下进行多种选择性转化,包括酸诱导的差向异构和/或逆环加成,还原,水解和醇解非常温和的条件。
One-pot reaction of ortho-acylphenols and terminal alkynoates for synthesis of 2-alkyl-substituted chromanones
A facile synthesis of 2-alkyl-substituted chromanones from ortho-acylphenols and terminal alkynoates is described. The method contains two consecutive processes in one-pot reaction through a DABCO-catalyzed condensation reaction and a KOBu'-mediated intramolecular cycloaddition to afford the desired products. (C) 2010 Elsevier Ltd. All Fights reserved.