Acrylates from ketene

The regiochemistry of ketene iminium salt cycloadditions can also differ from ketene cycloadditions. Whereas reaction of styrene with a series of ketene iminium salts gave 3-phenyI-cyclobutanones7 (60-70% yield) similar to the regiochemistry of ketene cycloadditions, reaction with a series of acrylates and a,/J-unsaturated ketones gave cyclobutanones 5 with regiochemistry opposite to what would be expected from electrostatic considerations of ketene cycloadditions.s... 

From ketene, CH2=C=0, by addition of formaldehyde to produce jS-propiolactone. jS-Propiolactone polymerizes in the absence of a catalyst, or after the addition of SnCl4 or H2SO4, to the corresponding polyester, which decomposes at 150°C to produce acrylic acid ... 

Polymerization of methacrylates is also possible via what is known as group-transfer polymerization. Although only limited commercial use has been made of this technique, it does provide a route to block copolymers that is not available from ordinary free-radical polymerizations. In a prototypical group-transfer polymerization the fluoride-ion-catalyzed reaction of a methacrylate (or acrylate) in the presence of a silyl ketene acetal gives a high molecular weight polymer (45—50). 

Such copolymers of oxygen have been prepared from styrene, a-methylstyrene, indene, ketenes, butadiene, isoprene, l,l-diphen5iethylene, methyl methacrjiate, methyl acrylate, acrylonitrile, and vinyl chloride (44,66,109). 1,3-Dienes, such as butadiene, yield randomly distributed 1,2- and 1,4-copolymers. Oxygen pressure and olefin stmcture are important factors in these reactions for example, other products, eg, carbonyl compounds, epoxides, etc, can form at low oxygen pressures. Polymers possessing dialkyl peroxide moieties in the polymer backbone have also been prepared by base-catalyzed condensations of di(hydroxy-/ f2 -alkyl) peroxides with dibasic acid chlorides or bis(chloroformates) (110). 

This reaction can also be used for the preparation of ketene silyl acetals from tt/l-unsaturated esters, including simple acrylates (72) in geometrically defined cases, the (Z) isomer is produced stereoselectively (7) ... 

Group transfer polymerization offers another route to LAP of (meth)acrylates without resorting to low temperatures [Hertler, 1994, 1996 Muller, 1990 Quirk et al., 1993 Reetz, 1988 Schubert and Bandermann, 1989, Sogah et al., 1987, 1990 Webster, 1987, 1992, 2000]. The initiator is a silyl ketene acetal (XXIV) that is synthesized from an ester enolate ... 

Olefin 6, aldehyde or ketone 8, acrylic acid 17 and ketene 18 can be found among the possible products generated unfinished states 15 and 19 did not seem to be promising. Complex 14 and 1,4-metalla diradical 4 formed from it by decarboxylation is an important intermediate. The ways terminating at olefin contain path 4-5-6 starting with decarboxylation and path 2-12-13-6, where the decarboxylation follows after the homolysis of the C —O bond of the original hydroxyl. Complex 14 can homolyse into 4 or 16, in both cases diradicals produce... 

Acrolein and condensable by-products, mainly acrylic acid plus some acetic acid and acetaldehyde, are separated from nitrogen and carbon oxides in a water absorber. However in most industrial plants the product is not isolated for sale, but instead the acrolein-rich effluent is transferred to a second-stage reactor for oxidation to acrylic acid. In fact the volume of acrylic acid production ca. 4.2 Mt/a worldwide) is an order of magnitude larger than that of commercial acrolein. The propylene oxidation has supplanted earlier acrylic acid processes based on other feedstocks, such as the Reppe synthesis from acetylene, the ketene process from acetic acid and formaldehyde, or the hydrolysis of acrylonitrile or of ethylene cyanohydrin (from ethylene oxide). In addition to the (preferred) stepwise process, via acrolein (Equation 30), a... 

If the reaction between enol silyl ethers and a,/ -unsaturated ketones is attempted in the presence of a titanium Lewis acid, the mode of the reaction switches to 1,4-addition with reference to the unsaturated ketone [109-113]. The reaction of an enol silyl ether is shown in Eq. (30) [114]. Ketene silyl acetals react with a,j8-unsaturated ketones in similar 1,4-fashion, as exemplified in Eq. (31) [115]. Acrylic esters, which often tend to polymerize, are also acceptable substrates for a, -unsaturated carbonyl compounds [111]. A difluoroenol silyl ether participated in this cationic reaction (Eq. 32) [116], and an olefinic acetal can be used in place of the parent a-methylene ketone [111] to give the 1,5-diketone in good yield (Eq. 33) [117]. More results from titanium-catalyzed 1,4-addition of enol silyl ethers and silyl ketene acetals to a,f -unsaturated carbonyl compounds are summarized in Table 4. 

Some thermally forbidden [2 + 2]-cycloaddition reactions can be promoted by Lewis acids1-6. With chirally modified Lewis acids, the opportunity for application in asymmetric synthesis of chiral cyclobutanes arises (for a detailed description of these methods see Sections D.l. 6.1.3.. D.l. 61.4. and references 7, 28-30). Thus, a chiral titanium reagent, generated in situ from dichloro(diisopropoxy)titanium and a chiral diol 3, derived from tartaric acid, catalyzes the [2 + 2]-cycloaddition reaction of 2-oxazolidinone derivatives of a,/ -unsalurated acids 1 and the ketene thioacetal 2 in the presence of molecular sieves 4 A with up to 96 % yield and 98% ee. Fumaric acid substrates give higher yields and enantiomeric excesses than acrylic acid derivatives8. Michael additions are almost completely suppressed under these reaction... 

Stanforth and co-workers made additional improvements on the hetero-Diels-Alder approach. They accomplished a one-pot synthesis of pyridines from a p-diketoesters and amidrazones <04T8893>. Deniaud et al. has investigated diazadienium iodide 15 as an aza-diene moiety in the synthesis of pyridines <04TL9557>. They have demonstrated that diazadienium iodide 15 reacts with ketenes, acetylenes and acrylic dienophiles to yield a variety of substituted pyridines as shown in Scheme 5. 

The free radical polymerizations of cyclic ketene acetals have recently evoked a lot of interest (10-13). TTie oly(e-caprolactone) (PCL) can be synthesized by free radical ring opening polymerization (10). The copolymerization of its monomer, 2-methylene-l,3-dioxepane (MDO), with some vinyl monomers resulted in an aliphatic ester backbone, as well as the pendant functional groups from the vinyl monomers (10). By free radical polymerization of MDO and the vinyl monomers vinylphosphonic acid (VPA), dimethylvinylphosphonate (VPE) and acrylic acid (AA), we synthesized a series of biodegradable copolymers including PCL... 

In the benzo[g]indolizine series, the ester (756) has been obtained from the isoquinolium ylide (755 R = C02Et) and cyclopentanone (which is a synthetic equivalent of cyclopentyne), acetic anhydride reacts with the ylide to afford the acetoxy-derivative (757), and the action of keten on the cyano-analogue (755 R = CN) leads to the ketone (758)/ Diphenylcyclopropenone combines with 1-methyl-3,4-dihydroisoquinoline to form the rearranged adduct (759). The benzo[e]indolizine (761) is one of the products of the thermolysis of the azide (760). Heating indoline with acrylic acid in polyphosphoric acid gives a mixture of the tri- and tetra-cyclic compounds (762) and (763). ... 

Addition and Cyclization Reactions. Benzocyclobutenone undergoes ring opening on flash photolysis, to afford 6-methylene-2,4-cyclohexadienyl-ketene. A report has given details of the highly selective sequential addition and cyclization reactions illustrated in Scheme 6. The reactions in Scheme 6 show the results with -butyl acrylate, but other acrylate derivatives are also effective." Hoffmann and Goerner" have studied the electron transfer from... 

In analogy to acrylic acid, methyl acrylate is produced from acetylene, ethylene or ketene, in which case, the water is replaced by methanol. Higher alcohol acrylic esters are obtained from methyl acrylate by transesterification. 

Ketene-imine cycloaddition involving an imine derived from cinnam-aldehyde and a D-glucosamine derivative led stereoselectively to the p-lactam (110) the chiral auxiliary could be disconnected from the p-lactam by base treatment. Cycloaddition of methyl acrylate and an N-glycosyl dihydropyridine gave adduct (111) and its diastereomer in the azabicyclic ring system. Removal of the chiral auxiliary from each diastereomer then gave the enantiomeric isoquinuclidines. ... 

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