Vinyl palladium-catalyzed carbonylative

The palladium-catalyzed carbonylation of 4-amino-2-alkynyl carbonates 40 or 5-hydroxy-2-alkynyl carbonates 41 afforded a-vinylidene-/i-lactams 42 [60] or a-vinyl-idene-y-lactones 43 [61] in good yields (Scheme 3.25). The initially formed (allenyl-carbonyl)palladium(II) intermediates were trapped by the intramolecular amino- or hydroxy-nucleophiles to give 42 or 43. 

In an alternative strategy functionalized phenols, such as iodophenol, were involved in palladium-catalyzed carbonylation of alkynes or allenes, producing coumarin or chromone derivatives (Scheme 23) [130-133]. After oxidative addition of the iodoarene to the Pd(0) catalyst the order of insertion of either CO or the unsaturated substrate mainly depends on the nature of the substrate. In fact, Alper et al. reported that CO insertion occurs prior to allene insertion leading to methylene- or vinyl-benzopyranone derivatives [130]. On the contrary, insertion of alkynes precedes insertion of CO, affording couma-rine derivatives, as reported by Larock et al. According to the authors, this unusual selectivity can be explained by the inability of the acyl palladium species to further react with the alkyne, hence the decarbonylation step occurs preferentially [131-133]. 

The palladium-catalyzed carbonylation of isomeric vinylic halides shows the reaction to be reasonably stereospecific and proceed with retention of the original halide structure. The degree of specificity, however, depends somewhat on the reaction conditions. Low reaction temperatures and/or excess triarylphosphine favor the stereospecific reaction (11). 

Unsymmetricatl ketones can be obtained by the palladium-catalyzed carbonylation of aryl, alkyl and vinyl bromides and iodides in the presence of tetraalkyl- or tetraaryl-tin compounds (equation 113).489,490 The catalyst precursors used were complexes (102), (107) and [PdCI2(AsPh3)2]. 

The palladium-catalyzed carbonylation reaction of allyl diethyl phosphate, in the presence of imines, gives either cis- or rraws-3-vinyl-/J-lactams, in high yields and in a stereoselective fashion (equation 160)574,575. The reaction is a [2 + 2] cycloaddition process which occurs under simple and mild conditions and has significantly more potential than the reaction of imines with ketenes (due to the more forcing conditions that are usually required to form the ketene intermediates). This reaction, however, only proceeds in low yield if the allyl phosphate is replaced with allyl acetate576. 

After separation of the desired major diastereoisomer 154, the removal of the chiral auxiliary furnished vinyl compound 151 in enantiomerically pure form. The latter was directly converted to the 9-membered lactam 144 in 58% yield via a palladium-catalyzed carbonylation (10 atm CO, HCOOH, DME, 150°C). Removal of the methyl ester as previously described furnished (-)-rhazinilam. This elegant work constitutes the first asymmetric total synthesis of the natural product. 

The construction of -silyl divinyl ketones in many different structural settings has been weU developed. The four principal connections outlined in Scheme 16 are as follows path a, vinyl organome-tallic addition to 3-trimeAylsilyl-2-propenal path b, 3-trialkylsilylvinyl organometallic" addition to enals path c, palladium-catalyzed carbonylation/coupling of 2-trimethylsilylvinyltrimethylstan-nane and path d, acylation of a B-silyl copper reagent. 

Gyorkos, A. C., Stille, J. K., Hegedus, L. S. The total synthesis of ( )-epi-jatrophone and ( )-jatrophone using palladium-catalyzed carbonylative coupling of vinyl triflates with vinyl stannanes as the macrocycle-forming step. J. Am. Chem. Soc. 1990,112, 8465-8472. 

Alkenyl substituents attached to aziridine ring carbons allow a palladium-catalyzed carbonyl-insertion reaction to occur, producing a /1-lactam (Scheme 46) <91SL91>. The proposed mechanism <93BMC2415> is based on an analogous reaction of vinyl epoxides <85JA6123>. Initial attack of palladium(O) on the optically active /ra .s-vinylaziridine (67) leads to the zr-allyl palladium complex... 

Tanaka and his associates demonstrated for the first time how to use non-volatile ionic liquids (ILs) as solvents in palladium-catalyzed carbonylations [163], In the case of alkoxycarbonylation of bromobenzene, higher yields were obtained when 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] was used as the reaction medium compared with standard conditions. And the selectivity for the monocarb-onylation of iodobenzene with t -PrOH or Et2NH was significantly enhanced by [bmim][BF4]. After separation of the products, the solvent-catalyst system was easily recycled and exhibited catalytic activity up to seven times. Since then the replacement of traditional solvents with quaternary ammonium halides, imidazoli-um- or pyridinium-derived ILs has gained increasing importance [164—173]. Recently, the phosphonium salt IL trihexyl(tetradecyl)phosphonium bromide has proven to be an effective reaction medium for various carbonylation reactions of aryl and vinyl bromides or iodides under mild conditions (Scheme 2.17) [174]. 

Gennari and his group reported a more sophisticated palladium-catalyzed carbonylative coupling of vinyl stannanes with electron-poor enol triflates [61]. The effect of ligands and additives was tested, and a combination of Pd2dba3, AsPh3, LiCl, Cul and NMP proved to be the optimal system. Later, this methodology was applied to the total synthesis of sarcodictyins [62]. 

The first palladium-catalyzed carbonylative Sonogashira coupling was reported in 1981 by Kobayashi and Tanaka [25]. Aryl, heterocyclic, and vinylic halides reacted with CO and terminal acetylenes at 120 °C and 80 bar in the presence of NEta and a catalytic amount of a palladium(II) complex to form alkynones in a 46-93 % yield (Scheme 5.3). Remarkably, aryl bromides and aliphatic alkynes were also included in the range of substrates. But NEts was used as a solvent for this transformation and a relatively high pressure of CO was needed. 

The first report on a palladium-catalyzed carbonylative C-H activation was published in 1986 by Kobayashi and Tanaka [1]. They reported that the carbonylation of organic halides with activated methylene compounds in the presence of NEta under 20 bar of CO produces various ketones in good yields (Scheme 6.1). Aryl iodides, bromobenzene and one example of a vinyl bromide were used as starting materials. But relatively high pressure and high pressure are needed, and tri-ethylamine was used both as a base and solvent. 

In 2007 the palladium-catalyzed coupling of aryl or vinyl iodides with ethyl diazoacetate was published by Wang and his team [7]. It was the first example of using a-diazocarbonyl compounds as a coupling partner in a palladium-catalyzed carbonylation reaction (Scheme 6.4). 

As vinyl triflates can be easily prepared from the corresponding ketones or aldehydes, which are abundant and wildly available, the use of vinyl triflates as starting materials in total synthesis has attracted a lot of attention [27—39]. Murai s group synthesized glycinoeclepin A by palladium-catalyzed carbonylation, using vinyl triflate as the key intermediate [40, 41]. Holt and colleagues prepared bioactive steroids [42, 43], whUe McDonald s team prepared cephalosporins [44]. 

A palladium-catalyzed carbonylative Strlle coupling of vinyl triflate was designed and used (Scheme 10.23). 

Uncinine is a novel butenolide alkaloid, isolated from Artabotrys uncinatus, a plant used as a traditional folk medicine in China for the treatment of nasopharyngeal carcinoma. Pour and colleagues did the total synthesis, and palladium-catalyzed carbonylation of vinyl iodide was applied (Scheme 10.32) [118]. 

D-homosteroid isolated from a marine source. In 2008 Chen s group reported the total synthesis of this compound by using a palladium-catalyzed carbonylative Stille-coupling of vinyl triflate as the key step (Scheme 10.37) [123, 124]. 

The first palladium-catalyzed carbonylations of aryl halides were published in 1974 and 1975 (Equation 17.59). ° Heck first reported the synthesis of benzoates by the reaction of an aryl iodide, carbon monoxide, and an alcohol in the presence of a tertiary amine and catalytic amoimts of the combination of palladium acetate and triphenylphosphine. Concurrently, he reported the synthesis of benzamides from an aryl iodide, carbon monoxide, a primary amine, and a tertiary amine as base catalyzed by the same type of palladium complex. The related reactions of vinyl halides were also reported, and these reactions occurred with retention of the olefin geometry. ... 

VI.2.1.1.1 Palladium-Catalyzed Carbonylation of Aryl and Vinylic Halides... 

B.i. Palladium-Catalyzed Carbonylation of Aryl or Vinyl Halide... 

The arylation of sodium cyanide can be achieved in moderate yields with electron-withdrawing iodonium salts [87]. The synthesis of esters was achieved by palladium-catalyzed carbonylative reaction of alcohols with diaiyliodonium salts under a CO atmosphere [262]. More recently, a base-mediated arylation of qui-nones with electron-donating iodonium salts in refluxing DCE was reported in moderate to good yields [263]. Quinoline anilides could be arylated at the P-carbon by a Pd- or Ni-catalyzed reaction proceeding via activation of sp C-H bonds (Scheme 22a) [264, 265]. Vinyl isocyanides were arylated at room temperature in a photoredox-catalyzed system with an iridium catalyst and visible light, followed by cyclizatimi to give isoquinoline derivatives [266]. 

Chemoselective carbonylation of a vinyl iodide 34 with alcohol containing a vinyl bromide moiety 35 has been successfully employed for the solid-phase synthesis of a macrosphelide precursor 36 [43]. After the 4-methoxyphenylmethyl (MPM) group was removed, the palladium-catalyzed carbonylative macrolactonization of the vinyl bromide 37 achieved the synthesis of the macrosphelide-supported derivative 38 (Scheme 9.13). The combinatorial synthesis of a 122-member macrosphelide library has been performed by the three-component strategy based on the palladium-catalyzed chemoselective carbonylation/macrolactonization reaction. 

Hydroxycarbonylation of vinyl triflates/halides has received considerable attention. The formation of carboxylic acids from palladium-catalyzed carbonylation of vinyl triflates is presumed to occur through the intermediacy of an unstable mixed anhydride. Hydroxycarbonylation of vinyl triflates has been reported to occur at room temperature in DMF under a CO balloon in the presence of Pd(OAc)2(PPh3)2 and potassium acetate [55]. The crucial role of the acetate anion is supported when the starting triflate is recovered after it has been reacted under usual conditions omitting potassium acetate. Acrylic acids have been obtained by palladium-catalyzed... 

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