catalyzed carbonylation of allenyl ketones has been investigated. Carbonylative dimerization predominantly proceeded to afford bis(3-furanyl)methanones 2 as the major products. The use of DMSO strikingly changed the course of the reaction, affording methyl 3-furancarboxylates 3 as the major products. DFT calculations revealed that DMSO stabilized the methanol-coordinated intermediate, leading to methoxycarbonylation
A new furan annelation by the palladium-catalyzed reaction of 2-alkynyl carbonates with β-keto esters is described. The reaction proceeds under mild neutral conditions and hence unstable 3-alkylidene-2,3-dihydrofurans can be prepared in this way. Similarly, reaction of 2-(1-alkynyl)oxiranes with β-keto esters gives alkylidene furans.
Highly selective synthesis of tetra-substituted furans and cyclopropenes: copper(i)-catalyzed formal cycloadditions of internal aryl alkynes and diazoacetates
作者:Andrew K. Swenson、Kate E. Higgins、Matthew G. Brewer、William W. Brennessel、Michael G. Coleman
DOI:10.1039/c2ob26295a
日期:——
A convenient Cu(I)-catalyzed cycloaddition of electron rich internal aryl alkynes and diazoacetates was discovered for the chemoselective and regioselective synthesis of tetra-substituted furans and cyclopropenes in moderate isolated yields (18–67%), and alkyne conversion (29–73%).
A new three-component cyclization−coupling reaction catalyzed by palladium was developed, producing polysubstituted furans in good yields from readily available substrates. The reaction conditions and the scope of the process were examined, and a possible mechanism is proposed.
Furan Synthesis via Triplet Sensitization of Acceptor/Acceptor Diazoalkanes
作者:Siqi Zhu、Fang Li、Claire Empel、Sripati Jana、Chao Pei、Rene M. Koenigs
DOI:10.1002/adsc.202200654
日期:2022.9.20
reaction of acceptor/acceptor diazoalkanes with terminal alkynes. Experimental and computational studies suggest the formation of a key triplet carbene intermediate that undergoes an addition reaction to the alkyne followed by cyclization to give furan heterocycles (31 to 90% yield). This reaction was studied with a broad range of alkynes and acceptor/acceptor diazoalkanes and now provides access to furans