A Metathesis-Based Approach to the Synthesis of Furans

Abstract

The enol ether-olefin ring-closing metathesis reaction has been employed to generate 2,3-dihydrofurans that are equipped with a leaving group. These substrates are at the correct oxidation state to undergo an acid-catalyzed aromatization, and this strategy has been utilized to provide a mild and rapid route (four steps) to a range of novel 2,5-disubstituted furans. [reaction: see text]

Metal-catalyzed Furan Synthesis. A Review

“…37 The cyclization is shown to occur in moderate yields for all of the reported examples, however when R 2 = CF 3 no reaction occurs and the preparation of the diene substrates requires three steps. Attempts to obtain trisubstituted furans by this method were less successful with one reaction failing and a second providing only a low yield of product.…”

Olefin‐Metathesis‐Based Synthesis of Furans by an RCM/Deprotonation/Phosphorylation Sequence and Their Diels–Alder Reactions

“…Signal assignments refer to the numbering schemes detailed in the Supporting Information. 13 C NMR spectra were recorded with a Bruker DRX 300 spectrometer at 75 MHz in CDCl 3 with CDCl 3 (δ = 77.0 ppm) as internal standard. IR spectra were recorded with a Nicolet Impact 400 D spectrometer as films in NaCl or KBr plates or as KBr discs.…”

“…[1,2] Reactions previously described in the literature can be classified as assisted tandem catalytic [3] RCM/aromatization sequences, [4][5][6] one-flask sequences comprising an Ru-catalysed RCM step followed by an oxidation [7][8][9][10] or elimination reaction, [11][12][13] and twostep procedures involving isolation of the RCM product, which is then converted into an aromatic compound. [14,15] Due to the significance of substituted furans as synthetic intermediates and as structural elements in various drugs and drug candidates, we started to explore metathesis-based routes for the synthesis of these aromatic heterocycles.…”

Transition Metal-Mediated Synthesis of Monocyclic Aromatic Heterocycles

“…222b,224 The reaction produces furans in moderate yields and is more efficient for the synthesis of disubstituted products. Cyclization of substrates possessing 1,1-disubstituted double bond of the homoallyl moiety, as well as bulky R 2 -substituents at the vinyl ether double bond was not efficient.…”