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The first examples of the carbonylation of mercaptans are described: cobalt carbonyl catalyzes the desulfurization and carbonylation of mercaptans to carboxylic esters by means of carbon monoxide in aqueous alcohol.Sir: Carbonylation reactions are an important class of organic reactions. Of industrial importance are those transformations utilizing olefins, alkynes, and halides as For example, benzylic halides as well as vinylic monoor dibromides can be carbonylated to acids by cobalt carbonyl (eq 1)3 or palladi~m (0)~ catalysts under (1) Wender, I., Pino, P., Eds. "Organic Synthesis via Metal Carbonyls"; (2) Falbe, J., Ed. "New Syntheses with Carbon Monoxide"; Springer (3) Alper, H.; des Abbayes, H.

[reaction: see text] A new allylstannane reagent on non-cross-linked polystyrene was developed for the first time. This support differs markedly from standard cross-linked polymers because it is completely soluble in organic solvents; moreover, the reactions can be conveniently monitored directly by standard 1H NMR methods. The allylstannane underwent a free radical reaction with an alkyl halide to form a new allyl appendage. Tin byproducts can be easily recovered from cold methanol as white crystalline solids.

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Free radical allylations were studied using (1) soluble non-cross-linked polystyrene supports, (2) carbohydrate scaffolds, and (3) a combination of both synthetic motifs. Allylations on these custom designer supports provide easily purified products, free of tin residues. A D-xylose carbohydrate scaffold bearing a bromoester was used for a diastereoselective allyl tin transfer thermally at 80 degrees C and with Lewis acids. This is the first example of a diastereoselective radical reaction directed by a removable polymer-supported carbohydrate auxiliary.