Palladium-catalysed reactions decarboxylation

A palladium-catalysed decarboxylative allylic rearrangement of IV-alloc indoles has been reported that can also be combined with a Suzuki-Miyaura cross-coupling reaction in a single pot transformation (Scheme 144) ... 

A synthesis of 2 -0-methyluridine has been carried out by a procedure in which the 3, 5 -0-TIPDS derivative of uridine was protected at N-3 by the p-methoxybenzyl group,208 and the "wobble position" nucleoside 2 -0-methyl-5-(methoxycarboxylmethyl)uridine has also been prepared by similar means.209 The 2 -0-allyl derivative (141) of uridine is accessible by a palladium-catalysed decarboxylation of (142), and a similar reaction is possible on an adenosine derivative.210 2 -0-Propargyl uridine can be prepared via the 2, 3 -0-dibutylstannylene derivative the triple bond of this derivative could then be converted into an unusual carboranyl group, the resultant structure being of potential use in the neutron capture therapy of cancer.211 A conference report has discussed the use of 2-(methylthio)-phenylthiomethyl (MPTM) ethers for protection of the 2 -hydroxyl group in oligoribonucleotide synthesis.212... 

The palladium-catalysed decarboxylation of /3-ketocarboxylates is an attractive new method for the production of allylically substituted compounds " (Scheme 10). The reaction is thought to involve Pd enolate complexes as intermediates. 

Palladium is a useful catalyst in several reactions which lead to keto-esters. p-Keto-esters react with allylic carbonates, with catalysis by palladium, in a decarboxylative allylation reaction. y-Keto-esters are prepared, in reasonable yield, by the palladium-catalysed regioselective oxidation of Py-unsaturated esters. y-Keto-esters are obtained in good yield by the palladium-catalysed Reformatsky reaction of ethyl bromoacetate and acid chlorides. Derivatives of y-ketopimelic acid are formed by the rhodium-carbonyl-catalysed reaction of derivatives of acrylic acid with carbon monoxide. A mild method for the conversion of propiolic esters into P-keto-esters via thiol addition has been reported (Scheme 63) it has been used in a formal synthesis of ( )-thienamycin. 

The ligand-free palladium-catalysed coupling of aryl iodides and bromides with potassium oxalate monoester results in a decarboxylation reaction yielding aromatic esters such as (112). Carbon-hydrogen substitution is involved in the decarboxylative acylation reaction of cyclic enamides with a-oxocarboxylic acids, which may yield acylated enamides such as (114). The reaction is likely to involve a cyclic vinylpalladium intermediate (113) which, after decarboxylation and reductive elimination yields the acylated product. ... 

In a novel carbon-carbon bond-forming reaction, catalysed by tetrakis(triphenylphosphine)palladium, allyl /8-keto-carboxylates are efficiently decarboxylated at room temperature to give y,5-olefinic ketones, alkylation taking place regioselectively at the carbon which originally bore the carboalkoxy-group e.g. Scheme 70). Diallylated by-products are observed in some cases. 

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