Facile Synthesis of Enantiomerically Pure 2‐ and 2,3‐Disubstituted Furans Catalysed by Mixed Lewis Acids: An Easy Route to 3‐Iodofurans and 3‐(Hydroxymethyl)furans

Abstract

Simple and efficient syntheses, catalysed by a mixed Lewis acid system (ZrCl(4)/ZnI(2)), of enantiomerically pure 2- and 2,3-disubstituted furan derivatives--including important synthons such as 3-iodofuran and 3-(hydroxymethyl)furan derivatives--from commercially available 3,4,6-tri-O-acetyl-D-glucal are described. The transformation is achieved through a synergistic interaction between ZrCl(4) and ZnI(2) in catalytic amounts.

A Survey of Recent Synthetic Applications of 2,3-Dideoxy-Hex-2-enopyranosides

“…Oxidative transformations of hex-2,3-enopyranosides are also of synthetic value since they might lead to unsaturated enones, unsaturated lactones, or 6-formyl derivatives, depending on the conditions employed. Oxidation of diols 94 can be attained regioselectively at either O -4, or O -6, to give enones, e.g., 95 [96,97,98,99,100,101], or aldehydes, e.g., 96 [102], respectively (Scheme 22). For example, ethyl 2,3-dideoxy-α- d -erythro-hex-2-enopyranoside ( 94 , R=Et) undergoes chemoselective allylic oxidation upon treatment with manganese dioxide or pyridinium dichromate to give hex-2-enopyranoside-4-ulose 95 , whereas selective oxidation of the primary hydroxyl group can be effected by a modification of the Corey-Kim procedure [103], as recommended by Fraser-Reid and co-workers, leading to aldehyde 96 [104,105,106].…”

Catalytic Enantioselective Arylation of Glyoxylate with Arylsilanes: Practical Synthesis of Optically Active Mandelic Acid Derivatives

“…The use of 0.1 to 0.005 mol % Pd complex under high concentration of 1r in toluene (5 or 10 M ) was sufficient to promote the reaction with good results although a longer reaction time was required (92 %, 99 % ee and 75 %, 98 % ee ). Furthermore, the catalyst loading could be reduced to 0.002 mol % (S/C=50 000), the desired product 3r 18 maintaining a high enantioselectivity was obtained in 46 % yield (TON=23 000) with 98 % ee . Under a similar condition (0.1 or 0.01 mol % in CH 2 Cl 2 ), N ‐Boc protected pyrrole 1 , 1a , 1b , 1c , 1d , 1e , 1f , 1g , 1h , 1i , 1j , 1k , 1l , 1m , 1n , 1p , 1q , 1r , 1s also gave the corresponding product 3 , 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , 3l , 3m , 3n , 3o , 3p , 3q , 3r , 3s in a good yield with high enantioselectivity (80 %, 99 % ee and 74 %, 98 % ee ).…”

Transition Metal-Mediated Synthesis of Monocyclic Aromatic Heterocycles

“…189 A similar process catalyzed by ZrCl 4 /ZnI 2 system for D-glucal derivatives was recently disclosed by Shaw. 190 Finally, Nagarapu demonstrated a very efficient two component synthesis of polyhydroxyalkyl- and C -glycosylfurans from β-keto esters and unprotected sugar aldoses. 191 …”