Metal-free annulative hydrosulfonation of propiolate esters: synthesis of 4-sulfonates of coumarins and butenolides
作者:Rodney A. Fernandes、Ashvin J. Gangani、Rupesh A. Kunkalkar
DOI:10.1039/c9nj06438a
日期:——
An efficient metal-free and cost-effective method for the synthesis of coumarin and butenolide 4-sulfonates has been developed involving addition of sulfonic acids to ethyl propiolates followed by lactonization.
Manganese‐Catalysed C−H Activation: A Regioselective C−H Alkenylation of Indoles and other (hetero)aromatics with 4‐Hydroxy‐2‐Alkynoates Leading to Concomitant Lactonization
A manganese‐catalyzed C−H bond alkenylation of indoles at C2‐position with 4‐hydroxy‐2‐alkynoatesleading to concomitantlactonization under removable directing group strategy has been disclosed. This lactonization strategy exhibits regioselectivity, a broad substrate scope, and a good functional group tolerance furnishing the products in low to high yields. The regioselectivity is guided by the electronic
Facile reaction of thiols and amines with alkyl 4-hydroxy-2-alkynoates in water under neutral conditions and ultrasound irradiation
作者:Antonio Arcadi、Maria Alfonsi、Fabio Marinelli
DOI:10.1016/j.tetlet.2009.02.106
日期:2009.5
This Letter describes an alternative protocol for the Michael addition of thiols to 4-hydroxy-2-alkynoates. The reaction proceeds at room temperature in water under ultrasound irradiation. With amines instead of thiols a sequential conjugate addition/lactonization reaction leads to important 4-amino-furan-2-one derivatives.
<sup>
n
</sup>Bu<sub>4</sub>NPF<sub>6</sub> promoted regioselective cascade synthesis of functionally embellished naphthofurans under acid, metal & solvent free conditions
作者:Abhishek Pareek、Ravikrishna Dada、Monika Rana、Anuj K. Sharma、Srinivasarao Yaragorla
DOI:10.1039/c6ra17411f
日期:——
n Bu4NPF6 mediated highly regioselective synthesis of functionally embellished naphthofurans has been achieved from easily available naphthols and propargyl alcohols through a cascade benzylation, oxacyclisation (5-exo dig) and isomerization undersolventfreeconditions. The reaction works in a short time through dibenzyl ether formation followed by the decomposition to the carbocation to furnish
The classical Ritter reaction on γ-hydroxy-α,β-alkynoic esters produced γ-N-acylamino-β-keto esters or ethyl 5-oxazoleacetates using alkyl or aryl nitriles, respectively. The γ-N-acylamino-β-keto esters resulting from alkyl nitriles are useful intermediates in the synthesis of a variety of building blocks. We also show that these can be converted into ethyl 5-oxazoleacetates using an additional step