The preparation of C-aryl glucals via palladium-catalyzed cross-coupling methods

Abstract

. Can. J. Chem. 72, 1262 (I 994).The C-aryl glucals 17-31 have been prepared by the palladium-catalyzed cross coupling of l-tributylstannyl-3,4,6-tri-0-(tert-butyldimethylsily1)-D-glcal (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 l-iodo-3,4,6-tri-0-(triisopropylsilyl)-~-glucal (16) and a variety of metalated aromatics, including ArZnC1, ArB(OH),, and ArB(OMe),. 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-0-(triisopropylsily1)-D-glucal (12) by a metalation-iodination sequence.RICHARD W. FRIESEN, RICHARD W. LOO et CLAUDIO F. S m o . Can. J. Chem. 72, 1262Chem. 72, (1994.On a prCparC les C-aryl glucals 17-31 par un couplage croisC catalysC par le palladium du 1-tributylstannyl-3,4,6-tri-0-(tert-butyldimCthylsily1)-D-glucal (11) et des brornures d'aryle. Le sous-produit principal de toutes ces rkactions est le dimkre 33, le produit d'homocouplage du produit 11. On peut aussi obtenir les C-aryl glucals 34-40 par un couplage catalysC par le palladium du 1-iodo-3,4,6-tri-0-(triisopropylsilyl)-~-glucal (16) avec une variktC de produits aromatiques mCtallCs comportant le ArZnC1, le ArB(OH), et ArB(OMe),. Les avantages de la dernikre mCthode incluent des rendements supCrieurs de couplage dans des conditions plus douces et la pr~paration avec un rendement Clevk du composC 16 directement 2 partir du 3,4,6-tri-0-(triisopropylsily1)-D-glucal (12) par une sequence de metallation et d'iodation.[Traduit par la RCdaction]

Cross‐Coupling Reaction of Saccharide‐Based Alkenyl Boronic Acids with Aryl Halides: The Synthesis of Bergenin

“…Initially, we decided to explore pathways for the preparation of boronic acid 4 a (Scheme ). Because an alkenyl sugar derivative is exposed to t BuLi during the course of the reaction, suitable protective groups that were not affected by strong bases during the course of reactions had to be chosen for the saccharide moiety (e.g., methoxymethyl ether (MOM),13, 14 tert ‐butyldiphenylsilyl (TBDPS),13, 15, 16, 17, 18 triisopropylsilyl (TIPS),13, 19, 20 di‐ tert ‐butylsilylene,13, 21 and tert ‐butyldimethylsilyl (TBS)22, 23. Tri‐TIPS‐protected glucal 2 , prepared by protection of commercially available D ‐glucal 1 with TIPS chloride and imidazole, was converted into 1‐lithiated intermediate 3 by treatment with 4.0 equivalents of t BuLi.…”

Studies Toward the Total Synthesis of Pluraflavin A

“…[26] Initial attempts to hydrogenate compound 22 resulted in hydrogenolysis of the southeast benzyl ester. Accordingly, the protecting group scheme was altered to avoid the formation of this product.…”

Synthesis of γ‐Lactones from Cycloocta‐1,5‐diene − Starting Materials for Natural‐Product Synthesis

“…Spectroscopic data of the racemates have been partially reported. [ [9]), 20.9 (2q, 12-CH 3 [8], 12-CH 3 [9]) ppm.…”