Synthesis of Dihydrofurans Substituted in the 2‐Position

Abstract

Many natural products and biologically active compounds contain the dihydrofuran subunit. Molecules incorporating either 2‐substituted, 2,2‐disubstituted 2,3‐ or 2,5‐dihydrofurans are widespread in the literature and represent key “molecular building blocks”. The preparation of substituted dihydrofurans remains a current challenge in organic synthesis and this microreview details the various routes employed for their synthesis in the literature to the end of 2004. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Synthesis of Dihydrofurans and Dihydropyrans with Unsaturated Side Chains Based on Ring Size‐Selective Ring‐Closing Metathesis

“…[1][2][3][4][5] The Annonaceous acetogenins, for instance, are prominent examples. They have attracted considerable interest over the past few decades due to their promising biological activities, such as antitumor or pesticidal activity.…”

Combined Rhodium/Gold Catalysis: From Propargyloxiranes to 2,5‐Dihydrofurans in One Pot

“…We were delighted to observe a smooth formation of the desired 2,5-dihydrofurans 4 from substrate 1a and arylboronic acids bearing different substituents in the o-, m-and p-positions (Table 3, entries 1-14), a thiophene ring (Table 3, entry 15), or a 2-naphthyl group (Table 3, entry 16). The one-pot process tolerates both electron-rich (Table 3, entries 2, 6,7,8,12,13) and electron-deficient aryl groups (Table 3, entries 3, 4, 5, 9, 10, 11, 14). The chemical yields were high in most cases.…”

“…Due to their importance as target molecules and synthetic intermediates, the development of synthetic approaches to functionalized 2,5-dihydrofurans is of major interest. [8] Our group has developed a highly efficient and stereoselective synthesis of 2,5-dihydrofurans by gold-catalyzed cycloisomerization of a-hydroxyallenes, [9] a method that has found various applications in target-oriented synthesis. [10] aHydroxyA C H T U N G T R E N N U N G allenes are normally prepared by copper-mediated [11] or copper-catalyzed [12] S N 2'-substitution of propargylA C H T U N G T R E N N U N G oxiranes or related electrophiles which takes place with high anti-selectivity in most cases, as does the palladium-catalyzed reaction of propargyloxiranes with organozinc, [13] organotin, [14] and organoboron reagents, [15] or with carbon monoxide.…”

Annelation of Benzimidazoles with α,β‐Acetylenic γ‐Hydroxyacid Nitriles and Hydrolytic Rearrangement of the Cycloadducts on Alumina

“…These functionalized dihydrofurans are promising candidates for drug design because the dihydrofuran structure is intrinsic for a number of natural (ascorbic and penicillin acids, derivatives of tetronic acid), and biologically active products (azadirachtin, clerodin, austocystin A, etc. ), [18,19] some of which show antibacterial, antifungicidal, [20] antiviral, [21] and antiAIDS properties. [21,22] Thus, the results contribute both to basic benzimidazole chemistry and provide a new prospective family of drug candidates.…”