An ultrafast synthesis of spiroketals by synergistic gold(I) and Sc(III) catalysis has been reported. Diverse 5,6-benzannulated spiroketals were rapidly constructed by the diastereoselective [4 + 2] cycloaddition between gold-generated enol ether and Sc(III)-catalyzed o-quinone methide intermediates. Ultrafast reaction rate, ambient reaction temperature, general scope, high yields, excellent diastereoselectivity
Facile alkylation of o-hydroxyarylaldehydes and α-formylketones with trialkylboranes
作者:Keiji Okada、Yasushi Hosoda、Masaji Oda
DOI:10.1016/s0040-4039(00)85435-0
日期:1986.1
Trialkylboranes readily undergo alkylation reactions with o-hydroxyarylaldehydes and α-formylketones via the dialkylboryl complexes.
三烷基硼烷容易通过二烷基硼基络合物与邻-羟基芳基醛和α-甲酰基酮发生烷基化反应。
Scandium (III)-Catalyzed Cycloaddition of <i>in situ</i>
Generated <i>ortho</i>
-Quinone Methides with Vinyl Azides: An Efficient Access to Substituted 4<i>H</i>
-Chromenes
作者:Nuligonda Thirupathi、Chen-Ho Tung、Zhenghu Xu
DOI:10.1002/adsc.201800565
日期:2018.9.17
convenient and practical synthesis of 4H‐chromenes from the readily accessible o‐hydroxybenzhydryl alcohols and vinyl azides has been achieved. The transformation proceeds through a cascade that involves formation of an ortho‐quinonemethide, [4+2]‐cycloaddition and elimination of hydrazoic acid. The reaction is well tolerated with respect to both the o‐hydroxybenzhydrols and the vinyl azides and affords
A convergent and highly stereoselective [4+2] cycloaddition of in situ‐generated ortho‐Quinone methides (o‐QMs) and azlactone enols has been successfully developed through a triple Brønsted acid catalysis strategy. This protocol provides an efficient and mild access to various densely functionalized dihydrocoumarins bearing adjacent quaternary and tertiary stereogenic centers in high yields with excellent
Enantioselective Synthesis of Spiro Chroman‐Isoindolinones via Formal (4+2) Cycloaddition of In Situ‐Generated
<i>ortho</i>
‐Quinone Methides with 3‐Methylene Isoindolinones
作者:Tao Wang、Bo Huang、You‐Qing Wang
DOI:10.1002/adsc.202200350
日期:2022.8.2
Using chiral phosphoric acids as organocatalysts, a formal asymmetric (4+2) cycloaddition of 3-methylene isoindolinone and in situ-generated ortho-quinone methide substrates is disclosed. This reaction exhibited a broad substrate scope with various substituted cyclic enamides and ortho-hydroxybenzyl alcohol derivatives to construct a series of spiro chroman-isoindolinones containing spiro-N,O-heterocycles