Acid From aryl mesylate

One of the challenges in the Suzuki-type cross-coupling is to extend this reaction from electron-rich aryl iodides, bromides, and triflates to less reactive aryl sulfonates and aryl chlorides, which show poor reactivity in terms of oxidative addition in the catalytic cycle. Aryl mesylates, benzenesulfonates, and tosylates are much less expensive than triflates, and are unreactive toward palladium catalysts. The Ni(0)-catalyzed Suzuki-type cross-coupling reaction of aryl sulfonates, including mesylates, with arylboronic acids in the presence of K3P04 has been reported [123]. 

The silver-catalyzed cycloisomerization of allenic carboxylic acids to butenolides was also reported by Marshall and co-workers.329 Starting from the enantiomerically enriched propargyl mesylate 390, palladium-catalyzed hydroxycarbonylation led to the chiral allenecarboxylates 391 which afforded the butenolides 392 upon treatment with silver nitrate (Scheme 114). Unfortunately, partial racemization could not be avoided in this two-step sequence. In a related study, Ma and Shi330 have shown that the combination of Pd(PPh3)4 and Ag2C03 promotes the cyclization of allenecarboxylates to the corresponding butenolides, accompanied by the introduction of aryl or alkenyl groups at C3. 

Pd-catalyzed carbonylation of aryl halides and triflates is a well-established process. Stephen L. Buchwald of MIT has now (/. Am. Chem. Soc. 2008,130, 2754) extended this transformation to much less expensive tosylates and mesylates such as 7. P-Amino acids have often been prepared from a-amino acids by Amdt-Eistert homologation. Geoffrey W. Coates of Cornell University has devised Angew. Chem. Int. Ed. 2008, 47, 3979) a more practical alternative, the direct Co-catalyzed carbonylation of an oxazoline 9 to the 2-oxazine-6-one 10. 

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