The preparation of <i>C</i>-aryl glucals via palladium-catalyzed cross-coupling methods

Abstract

The C-aryl glucals 17–31 have been prepared by the palladium-catalyzed cross coupling of 1-tributylstannyl-3,4,6-tri-O-(tert-butyldimethylsilyl)-D-glucal (11) and aryl bromides. The major by-product in all of these reactions is the dimer 33, the product of homocoupling of 11. Alternatively, the C-aryl glucals 34–40 can be obtained from the palladium-catalyzed coupling of 1-iodo-3,4,6-tri-O-(triisopropylsilyl)-D-glucal (16) and a variety of metalated aromatics, including ArZnCl, ArB(OH) 2 , and ArB(OMe) 2 . The advantages of the latter procedure include superior coupling yields under milder reaction conditions and the high yielding preparation of 16 directly from 3,4,6-tri-O-(triisopropylsilyl)-D-glucal (12) by a metalation–iodination sequence.