Preparation of dioxolane-type fluoren-9-ylidene acetals of carbohydrates and their hydrogenolysis with AlClH2 to give axial fluoren-9-yl ethers

Article abstract of DOI:10.1016/0008-6215(92)84177-T

cis-Hydroxyl groups of hexopyranosides reacted with 9,9-dichlorofluorene to give fluoren-9-ylidene acetals, hydrogenolysis of which with AlClH2 gave derivatives with axial fluoren-9-yl ether and equatorial hydroxyl groups. 1,6-Anhydro-2,3-O-fluoren-9-ylidene-β-D-mannopyranose (9) was an exception which gave a 2:3 mixture of 2-and 3-fluoren-9-yl ethers because of the marked distortion of the pyranose ring.The fluoren-9-yl ether groups could be removed easily by catalytic hydrogenation or by hydrogenolysis with the Lewis acid-type mixed hydride AlCl2H.