Palladium methyl acrylate oxidation

Other unsaturated substrates arylated by various diaryl iodonium salts included butenone, acrylic acid, methyl acrylate and acrylonitrile [46]. Allyl alcohols with diaryliodonium bromides and palladium catalysis were arylated with concomitant oxidation for example, from oc-methylallyl alcohol, aldehydes of the general formula ArCH2CH(Me)CHO were formed [47]. Copper acetylide [48] and phenyl-acetylene [49] were also arylated, with palladium catalysis. 

L-(+)-Tartaric acid (F) was then converted to iodide G, whose addition to methyl acrylate under the standard conditions of radical reactions furnished H. Hydrogenolysis of H over palladium black yielded the corresponding alcohol, whose Swern oxidation afforded I, another building block. 

In a palladium-mediated oxidative coupling reaction, alkenes such as methyl acrylate, acrylonitrile, or styrenes cyclize with 6- [(diinethylainino)methylene]amino -l,3-dimethyluracil to give the corresponding 6-substituted pyrido[2,3-[Pg.128]

Mitsubishi Chemicals Liquid Phase Palladium-Catalyzed Oxidation Technology Oxidation of Cyclohexene, Acrolein, and Methyl Acrylate to Useful Industrial Chemicals... 

Aerobic Palladium-Catalyzed Oxidation of Methyl Acrylate (MA) to 3,3-Dimethoxy Methyl Propionate Process Optimization and Scale-Up... 

While studying the palladium-catalyzed oxidation of methyl acrylate in methanol using oxygen as the oxidant to form 3,3-dimethoxy methyl propionate, we encountered all three of these problems. The initial experiments were... 

Scheme 11.1 shows the reaction mechanism ofthe palladium-catalyzed oxidation of methyl acrylate to 3,3-dimethoxy methyl propionate. 

Palladium oxidizes methyl acrylate in the presence of methanol to form 3-methoxy methyl acrylate and equimolar amounts of water with a reaction rate R3. Reduced Pd is reoxidized by the Fe/Gu cocatalyst with a reaction rate R2 producing a reduced Fe/Gu cocatalyst, which is reoxidized by oxygen. The palladium catalyst is also responsible for the formation of by-products from oxidation of methanol (methyl formate, dimethoxymethane). 3-Methoxy methyl acrylate... 

Amatore, Jutand et al. [42] have established that the oxidative addition of Phi to Pd°(OAc)(dppp) (generated from Pd(OAc)2 and 2 equiv dppp) gives the cationic complex PhPd(dppp)(dppp(0))+ this is followed by reaction of iodide ions released from Phi in the course of a catalytic reaction giving PhPdl(dppp) or/and PhPd(OAc)(dppp) whenever acetate ions are used as bases (Scheme 1.25). The reaction of PhPd(dppp)(dppp(0))+ with alkenes (styrene, methyl acrylate) is so slow that this complex must be considered as a transient complex on the way to PhPdl(dppp) and/or PhPd(OAc)(dppp). These two complexes, which exchange their anions (Scheme 1.25), are in equilibrium with the common cationic complex PhPd(DMF)(dppp)+ in DMF (Scheme 1.31) [43]. Consequently, two neutral phenyl-palladium(II) complexes are candidates, in addition to the cationic PhPdS(dppp)+, for the reaction with alkenes. The kinetics of the reaction of isolated PhPdX(dppp) (X = I, OAc) with electron-deficient, neutral and electron-rich alkenes in the absence of a base has been followed by P NMR spectroscopy in DMF. It emerges that PhPd(OAc)(dppp) reacts with styrene and methyl acrylate via PhPd(DMF)(dppp)+ that... 

Palladium(II)-mediated oxidative coupling reactions involving the indole nucleus have been studied extensively in the literature. Fujiwara et al. [8b] reported that the reaction of A-acetylindole (8) with methyl acrylate (4b) gives (ii)-methyl 3-(l-acetyl-l//-indol-2-yl)acrylate (9, 4%) and ( )-methyl 3-(l-acetyl-l//-indol-3-yl)acrylate (10, 20%), along with A-acetyl-2,3-bis(methoxycarbonyl)carbazole (12,9%) which was believed to be generated by an electrocyclization and subsequent dehydrogenation of a 2,3-dialkenylated indole intermediate (11, Scheme 9.1). 

The palladium(II)-assisted alkenylation of aromatic compounds has also been applied to the synthesis of heterocycles. A novel synthesis of pyrido[3,4-d] pyrimidines, pyrido[2,3-d]pyrimidines and quinazolines was developed by Hirota et al. [18] employing the palladium(ll)-promoted oxidative coupling of uracil derivatives and alkenes. l,3-Dimethyluracil-6-carboxaldehyde dimethylhydrazone (22), 6-dimethylaminomethylenamino-l,3-dimethyluracil (24) and ( )-6-(2-dimethylaminovinyl) uracil (26) all reacted with methyl acrylate in the presence of stoichiometric Pd(OAc)2, producing pyrido[3,4-ii]pyrimidine 23, pyrido[2,3-if]pyrimidine 25 and quinazoline 27, each apparently arising from direct arylation, 6ti electrocycliza-tion, and elimination of dimethylamine, in 67%, 89% and 64% yields respectively (Scheme 9.3). 

The palladium(II)-catalysed alkenylation of heterocycles has also been studied extensively. Fujiwara and coworkers [8b, 26] reported that the reactions of furan and thiophene with alkenes such as methyl acrylate and acrylonitrile in the presence of 2 mol% Pd(OAc)2 and 2 equiv of Cu(OAc)2 under atmospheric oxygen or air produced both 2-alkenylated and 2,5-dialkenylated products. This method, however, was not particularly synthetically useful due to the low yields of the reactions (0.3-39%). Tsuji and Nagashima [21] also observed that furans 31a-c reacted with acrylates 4b and 4c to produce monoalkenylated compounds 32a-c, where the furan has been functionalized solely at the 2-position (or the 5-position if the 2-position is substituted) in moderate to good yields. Even a furan with an electron-withdrawing substituent (2-furaldehyde, 31c) participated in the oxidative coupling to yield a moderate 34% yield of the arylation... 

The palladium(ll)-catalysed direct oxidative coupling reaction was also extended to other heterocycles, such as uracils. Hirota et al. [30] reported a simple method for the synthesis of 5-alkenylated uracil derivatives by treatment of 1,3-dimethyluracil (46) and 2, 3 -isopropylideneuridine (48) with methyl acrylate (4b) in the presence of 5 mol% Pd(OAc)2 and 2 equiv rcrt-butyl perbenzoate in refluxing acetonitrile (Scheme 9.7). The reaction successfully generated the corresponding alkenylated heterocycles 47 and 49 in 75% and 46% yields respectively. 

An intriguing variation of Catellani s reaction accomplished a selective crosscoupling of two different aryl halides and methyl acrylate (Scheme 5) [8,9], It was suggested that a difference in the rates of oxidative additions of the two differentially substituted aryl halides with the palladium(0) and the palladium(ll) complexes accounted for the reported reactivity. However, the mechanistic ratiraiale invoking palladium(IV) intermediates have not been supported by either an experiment or computations. 

The application of a different N-halogen source was described by Branco, Prab-hakar and coworkers [20]. In this case, acrylic acid derivatives underwent amination in the presence of bromamine-T to yield the corresponding aziridines as the major products. Aminobrominated side products were also observed in some cases. Scheme 4.3 shows a representative example for the oxidation of dimethyl acrylamide (Eq. (4.9)). The reactions were also investigated in the presence of stoichiometric amounts of palladium, as for example for methyl acrylate, which gave the corresponding aziridine as the only product [21]. The mechanism of this aziridination remains uncertain as both Pd(II) and Pd(IV) intermediates have been suggested, although without definite proof... 

Catellani and Lautens have independently reported unique palladium/ norbornene-catalyzed reactions of aryl halides, which mechanistically involve a reversible alkene insertion/p-carbon elimination process [11]. For example, iodobenzene reacted with 1-iodobutane and methyl acrylate to form the multiply-alkylated benzene 29 (Scheme 7.9) [12]. The following mechanism is proposed oxidative addition of phenyl iodide onto palladium generates phenylpalladium(ll) iodide. A double bond of norbornene inserts into the C-Pd bond to form an alkylpalladium species, which cleaves a C-H bond nearby to form the palladacycle 25. -Butyl iodide then reacts with 25 to form the Pd(IV) intermediate 26, which undergoes reductive elimination. Repetition of the cyclometalation/alkylation process leads to the formation of 27. Then, P-carbon elimination affords the arylpalladium species 28 together with norbornene. Subsequently, a Heck-type reaction takes place with methyl acrylate, giving rise to 29. 

A phenyl group on alkenes can serve as a leaving group via insertion/p-carbon elimination. When the P-ketoester 30 was treated with a palladium catalyst and an oxidant, cyclization took place to afford naphthalene 33 (Scheme 7.10) [13]. The authors proposed a mechanism in which the intermediary alkylpalladium species 31 undergoes syn-P-carbon elimination to produce 32 and a phenylpal-ladium species. The eliminated phenyl group Is trapped by methyl acrylate via the Heck reaction to form methyl cinnamate. Aromatization serves as a driving force for the catalytic C-C bond cleavage. 

Jia et al. (265) report the palladium(II)-catalyzed selective oxidation of methyl acrylate in SCCO2 to dimethyl acetal as a major product with excellent conversion and selectivity. Best results were obtained using PdCl2 with CuCl2 as... 

Finally, the combination of copper bromide as oxidant and ureas as nitrogen source enabled an intramolecular palladium catalyzed diamination of acrylates (Scheme 4.13) [37]. For methyl or ethyl esters, this process proceeds with excellent diastereoselectivity in favor of the syn-configured cyclic urea product... 

Vinyl carbanions derived from acrylic esters and their jS-phenyl derivatives react with several carbon electrophiles to give a-substituted and a,/8-disub-stituted derivatives. While /8>alkyl substituted acrylates have been shown to dimerize in the presence of potassium catalyst at 110 C. Three simple unsaturated esters undergo palladium(0)-catalysed codimerization with methylenecyc-lopropane to furnish methylenecyclopentanecarboxylic esters in reasonable yield. An efficient procedure for the oxidation of isatins to anthranilic acid esters has appeared. Methyl 2,4,6-tri-isopropylbenzoate forms a dipole-stabilized carbanion on reaction with Bu Li, which then reacts with carbon electrophiles [e.g. E = Bui, (CH3)2C0, or CH3CHO] to give a range of ester derivatives in good yield (Scheme 52). ... 

Alpha (2) A process for making methyl methacrylate, developed by Ineos Acrylics (now Lucite International) since 1990. Ethylene is carbonylated and methylated to produce methyl propionate, which is reacted with formaldehyde to produce methyl methacrylate. The first stage is homogeneously catalyzed by a palladium phosphine complex. The second stage is operated in the gas phase over a catalyst of cesium oxide on silica. Piloted by Davy Process Technology in 2002. The first commercial plant was opened in Singapore in 2008. The second was to be built in Texas by Mitsubishi Rayon for completion in late 2009. Lucite International received the 2009 Kirkpatrick Chemical Engineering Achievement Award for this development. Lucite is now a subsidiary of Mitsubishi Rayon. 

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