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.
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
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