Synthesis of polyfunctionalized furans from 3-acetyl-1-aryl-2-pentene-1,4-diones

Organocatalytic (Z/E)-Selective Synthesis of 3-Vinylnaphthofurans via a Formal (3 + 2) Cycloaddition

A formal (3 + 2) cycloaddition of 1,4-enediones with 2-naphthols was established under the catalysis of trifluoromethanesulfonic acid as an organocatalyst, leading to the efficient synthesis of structurally diverse 3-vinylnaphthofurans with high yields and excellent (Z/E)-selectivities (up to 96% yield, all >20:1 Z/E). This formal (3 + 2) cycloaddition involved a cascade reaction process, and the intramolecular hydrogen bond in the structure of 3-vinylnaphthofurans should play an important role in controlling the (Z/E)-selectivity of the newly formed vinyl group. Moreover, this class of 3-vinylnaphthofurans was discovered to have an axial chirality. This work provides an organocatalytic approach for constructing multi-substituted vinylnaphthofurans via a cascade reaction with excellent control of the (Z/E)-selectivity, which will serve as a useful strategy for synthesizing vinylnaphthofurans via in situ construction of the furan core and formation of the vinyl group.

Isolation and Synthesis of Novel Meroterpenoids from Rhodomyrtus tomentosa: Investigation of a Reactive Enetrione Intermediate

Rhodomyrtusials A-C, the first examples of triketone-sesquiterpene meroterpenoids featuring a unique 6/5/5/9/4 fused pentacyclic ring system were isolated from Rhodomyrtus tomentosa, along with several biogenetically-related dihydropyran isomers. Two bis-furans and one dihydropyran isomer showed acetylcholinesterase (AChE) inhibitory activity. Structures of the isolates were unambiguously established by a combination of spectroscopic data, ECD analysis, and total synthesis. Bioinspired total syntheses of six isolates were achieved in six steps utilizing a reactive enetrione intermediate generated in situ from a readily available hydroxy-endoperoxide precursor.

Understanding the high reactivity of carbonyl compounds towards nucleophilic carbenoid intermediates generated from carbene isocyanides

The high nucleophilic character of the carbenoid intermediate cis-IN together with the specific approach mode of acetone make the formation of the C–C single bond with a very low activation free energy, possible.

Three-Component Reaction between alkyl(aryl) Isocyanides and Dialkyl Acetylenedicarboxylates in the Presence of Ethyl Trifluoroacetate

The 1:1 intermediate generated by the addition of alkyl(aryl) isocyanides to dialkyl acetylenedicarboxylates is trapped by ethyl trifluoroacetate in the absence of a catalyst to form highly functionalized dialkyl 5-[alkyl(aryl)imino]-2-ethoxy-2-(trifluoromethyl)-2,5-dihydrofuran–-3,4-dicarboxylates in good yields.