Grignard with Merrifield resin

Another possibihty to release alcohols from ester resins is cleavage by carbon nucleophiles. Chandrasekhar et al. [88] proved the utiUty of diverse Grignard reagents for the cleavage of aliphatic as well as aromatic esters directly bound to Merrifield resin. Reactions were performed in THF/Et20 with three equivalents of Grignard reagent and furnished products in 65-88% yield. 

To our knowledge no possibility exists to cleave ester linkers with carbon nucleophiles to give ketones. In contrast, thioester linkers can be ap-pUed for these purposes as shown by Bradley et al. [89]. The thioester 55 in Scheme 8 was prepared easily by addition of an arylthioamide and sodiiun iodide to Merrifield resin in aqueous DMF. It was shown that thioesters without the need of special Hnker demands can be transformed into ketones 57 as well as into primary (60) and tertiary alcohols (59). The addition of Grignard reagents to thioesters gives tertiary alcohols whereas the addition of C-nucleophUes via organocuprates provides ketones in 53% yield. These results differ from those found by Vlattas et al. in 1997 who observed the... 

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