2-Aminofuran derivatives, synthesis

J.S. Yadav, B.V.S. Reddy, S. Shubashree, K. Sadashiv, J. Naidu, Ionic liquids-promoted multi-component reaction Green approach for highly substituted 2-aminofuran derivatives. Synthesis 14 (2004) 2376-2380. 

On the contrary, with aromatic aldehydes carrying electron-releasing groups (such as 4-CH3, or 4-OCH3), products were obtained in poor yields. Several significant advantages, such as operational simplicity, mild reaction conditions, enhanced rates, improved yields, ease of isolation of products, recyclability, and the eco-friendly nature of the solvent, make this method a useful and attractive strategy for the synthesis of 2-aminofuran derivatives. 

Scheme 17.1 Synthesis of 2-aminofuran derivatives using [bmim]BF ...

An efficient method for the synthesis of 2-aminofuran derivatives was described. Regioselectivity was achieved through either a metal-based catalytic or an organocatalytic approach (14CAJ3413). 

SCHEME 5.8 Thiazolium-mediated MCR for the synthesis of 3-aminofuran derivatives 13. C02Me -... 

Styryl derivatives of 2-aminofurans, as well as alkenyl compounds, also undergo intramolecular cycloaddition and the alkene function can be introduced by Stille coupling of a suitably functionalised aryl iodide. This approach is illustrated by the tetrahydroquinoline synthesis summarised in Scheme 26 (99JOC3595). The iodo derivative 143 is readily prepared from the carbamate ester 142 (67% yield) and Stille coupling with vinyltributyltin gives the styrene 144 (72% yield). Intramolecular cycloaddition and dehydration is then achieved simply by heating compound 144 in toluene under reflux (24 h) to give the tetrahydroquinoline 145 in 79% yield. 

The [4-1-3] cycloaddition between 2-aminofuran and oxyallyl cations, followed by base-induced elimination of the resulting adducts, was used in the synthesis of 3-aminotropones <05TL8475>. A chiral Lewis acid-catalyzed [4t-3] cycloaddition between furans and nitrogen-stabilized oxyallyl cations derived from allenamides was developed. As depicted below, the Cj-symmetric salen-based ligand is the most effective in promoting this asymmetric cycloaddition reaction <05JA50>. 

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