Palladium catalysed acetalization

There are also palladium-catalysed procedures for allylation. Ethyl 3-bromo-l-(4-methylphenylsulfonyl)indole-2-carboxylate is allylated at C3 upon reaction with allyl acetate and hexabutylditin[27], Ihe reaction presumably Involves a ir-allyl-Pd intermediate formed from the allyl acetate, oxidative addition, transmetallation and cross coupling. 

Moreover, a few chiral ferrocenylsulfur-imine ligands were investigated in the palladium-catalysed asymmetric allylic alkylation of 1,3-diphenylpropenyl acetate and cyclohexenyl acetate with dimethyl maionate (Scheme... 

Trost and coworkers have devised a stereocontrolled 1,3-diene synthesis employing a palladium-catalysed decarboxylative elimination procedure from allylic acetates carrying carboxylic acid functionality ji- to the acetate group (equation 18)48. This decarboxylative elimination strategy has been applied to the synthesis of an insect pheromone, codlemone48a and the ethyl ester of vitamin A carboxylic acid (Table 5)48b. 

The diester 226 undergoes ring-closure to the methylenecyclopentane derivative 227 in the presence of a catalytic amount of chlorotris(triphenylphosphine)rhodium in boiling chloroform saturated with hydrogen chloride. In contrast, if the reaction is catalysed by palladium(II) acetate, the isomeric cyclopentene 228 is produced (equation 115)118. 

Leadbeater NE, Pillsbury SJ, Shanahan E, Williams VA (2005) An assessment of the technique of simultaneous cooling in conjunction with microwave heating for organic synthesis. Tetrahedron 61 3565-3585 Lee CKY, Holmes AB, Ley SV, McConvey IF, Al-Duri B, Leeke GA, Santos RCD, Seville JPK (2005) Efficient batch and continuous flow Suzuki crosscoupling reactions under mild conditions, catalysed by polyurea-encapsulated palladium (II) acetate and tetra-n-butylammonium salts. J Chem Soc Chem Commun 2175-2177... 

The palladium catalysed substitution reaction of allylic systems has also been utilised in the formation of five membered rings. Intramolecular nucleophilic attack of the amide nitrogen atom on the allylpalladium complex formed in the oxidative addition of the allyl acetate moiety on the catalyst led to the formation of the five membered ring (3.63.). In the presence of a copper(II) salt the intermediate pyrroline derivative oxidized to pyrrole.80... 

Intermolecular cyclopropanation of diazoketones is an effective method in organic synthesis. Wenkert and coworkers have applied this methodology to the synthesis of a substantial number of cyclopropane adducts 2868, 2969 and 307° which are synthetic intermediates in the preparation of natural products (equations 41—43). Copper catalysts were chosen for these transformations. Another interesting application of intermolecular cyclopropanation is to be found in Daniewski s total synthesis of an aromatic steroid. Palladium(II) acetate catalysed decomposition of 4-bromo-l-diazo-2-butanone in the presence of m-methoxystyrene was used to give the cyclopropyl ketone 31 which was a key intermediate in the total synthesis (equation 44)71. 

Experimental KTEs and theory were used to investigate the mechanism of the palladium-catalysed alkylation of 1,1-dimethylallyl acetate (2) by dimethyl malonate.6 The transition structure in THF is believed to have long Pd-C bonds and significant Sn 1 character, as described earlier. 

The palladium-catalysed allylic alkylation of dimethylallyl acetate 35 with dimethyl malonate 36 in THF at 25°C was carried out using a combination of Pd2(dba)3 [fris(dibenzylideneacetone)dipalladium] and triphenylphosphine with 0,N-Ws(trimethylsilyl)acetamide (BSA) as a base.87... 

The 3-acetoxymethylazepine 18 formed by RCM of the corresponding allyl acetate 17 underwent palladium-catalysed allylic reduction to give almost exclusively the 3-exo-methylene isomer 19 <07JOC2674>. 

Figure 4.88 Palladium catalysed reaction between 1,3-diphenylpropenyl acetate and dime-...

Evans J, O Neill L, Kambhampati VL, Rayner G, Turin S, Genge A, Dent AJ, Neisius T (2002) Structural characterisation of solution species implicated in the palladium-catalysed Heck reaction by Pd K-edge X-ray absorption spectroscopy palladium acetate as a catalyst precursor. J Chem Soc, Dalton Trans 10 2207... 

Many further examples of reactions in which phosphate anions act as leaving groups have been reported. Palladium-catalysed reactions of cyclic ketene acetal phosphates, e.g. 64, are reported to offer advantages over the corresponding... 

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