Acyclic Carbonic Esters

Cleavage of lactones and carbonates. Lactones and carbonates react with bromotrimethylsilane to afford bromocarboxylic acid derivatives (equation I) and bromohydrin trimethylsilyl ethers (equation II), respectively acyclic, aliphatic esters do not react with bromotrimethylsilane. lodotrimethylsilane reacts in an analogous fashion with lactones, but in reaction with ethylene carbonate the main product is 1,2-diiodoethane (equation III). The >-bromocarboxylate derivatives are converted into acid chlorides by reaction with SOCL (equation I). 

The chemical produced in the greatest amount through CO2 utilization is urea. According to the international fertilization association, 157 million tons of urea were produced in 2010. Other chemicals produced through CO2 utilization are cyclic carbonates, acyclic carbonates, polyalkylene carbonates, Asahi Kasei polycarbonates, carbamic acid esters, oxazolidinones, polyurethanes, carboxylic acids and esters, lactones, formic acid, and methanol. The amounts of various organic chemicals produced through carbon dioxide utilization throughout the world are shown in Table 9.3 [88]. 

Enantioselective allylic substitutions of cyclic allylic esters have been more challenging to develop than enantioselective reactions of symmetrical, acyclic allylic esters. In one set of reactions, racemic allylic esters react to form non-racemic products by addition of carbon or nitrogen nucleophiles in the presence of palladium catalysts. In these cases, attack at the two termini of the allylic intermediate generates the two enantiomers. Only a handful of ligands have generated catalysts that form products from the substitution of aliphatic. 

The fluorination of cyclic ethers, esters, lactones, and cyclic and acyclic carbonates can be achieved by anodic oxidation of a large amount of the liquid substrates and a small amormt of Et4NF-4HF (only 1.5—1.7 equiv. of F to the ether) at a high current density (150 mA cm ) (Schemes 17 and 18) [27]. 

The mechanism of the Cook-Heilbron reaction between a-aminonitriles and dithioformic ester 6 proceeds via an acyclic intermediate 7, as proven by its isolation in several cases. Nucleophilic attack of the amine function on the sulfur-bearing carbon leads to the elimination of hydrogen sulphide. Cyclization of the acyclic thiacetoamide results in a five membered ring which aromatises favourably to give 5-amino-2-benzylthiazole 8. 

The use of nonstabilized carbon nucleophiles in this reaction has been rare. Recently, however, it was shown that lithium ester enolates participate in Pd-cata-lyzed 1,4-additions to cyclic and acyclic vinyloxiranes, affording the corresponding 6-hydroxy-4-enoates in good yields and with complete regioselectivity [117, 118]. 

Nearly all of the polymers produced by step-growth polymerization contain heteroatoms and/or aromatic rings in the backbone. One exception is polymers produced from acyclic diene metathesis (ADMET) polymerization.22 Hydrocarbon polymers with carbon-carbon double bonds are readily produced using ADMET polymerization techniques. Polyesters, polycarbonates, polyamides, and polyurethanes can be produced from aliphatic monomers with appropriate functional groups (Fig. 1.1). In these aliphatic polymers, the concentration of the linking groups (ester, carbonate, amide, or urethane) in the backbone greatly influences the physical properties. 

A titan acycl open tadi en e generated from an acetylene having an ester group at a suitable position reacts intramolecularly with this functional group, as exemplified by Eq. 9.13. Here, both carbon—titanium bonds of the titanacycle participate in the reaction to effect ring-closure [33]. 

The carbanion derived from dimethyl malonate reacts with the cyclic nitro compounds 422 of ring size 5, 6, 7, 8 and 12 to afford the corresponding esters 423. Acyclic allylic nitro compounds 424 (R = Me, CH2OAC or CC Et) are attacked by bulky nucleophiles, such as dimethyl malonate anion, mainly at the terminal primary carbon atom to give rearranged products 425, whereas smaller nucleophiles, e.g. the anion derived from methyl cyanoacetate, react at the tertiary carbon atom to yield 426409a 453 455. 

An interesting observation should be made concerning the dependence of the physical properties on molecular cyclicity, since it will have a significant effect on the formulation of electrolytes for lithium ion cells. While all of the ethers, cyclic or acyclic, demonstrate similar moderate dielectric constants (2—7) and low viscosities (0.3—0.6 cP), cyclic and acyclic esters behave like two entirely different kinds of compounds in terms of dielectric constant and viscosity that is, all cyclic esters are uniformly polar (c = 40—90) and rather viscous rj = 1.7—2.0 cP), and all acyclic esters are weakly polar ( = 3—6) and fluid (77 = 0.4—0.7 cP). The origin for the effect of molecular cyclicity on the dielectric constant has been attributed to the intramolecular strain of the cyclic structures that favors the conformation of better alignment of molecular dipoles, while the more flexible and open structure of linear carbonates results in the mutual cancellation of these dipoles. 

The formation of tluorinated Q -hydroxy-jS-imino esters (180) by treatment of fluorinated imino ethers (179) with lithium 2,2,6,6-tetramethylpiperidide has been reported. A possible explanation for this interesting intramolecular rearrangement is proposed in Scheme 64. Acyclic imides derived from primary benzylic amines and amino acid esters have been found to undergo a novel nitrogen to carbon acyl migration via a base-generated carbanion to yield the corresponding a-amino... 

The first organocatalyzed conjugate addition of a-substituted p-ketoester to a,P-unsaturated ketones was presented by Deng et al. [42] (Scheme 3). Although traditional Cinchona alkaloids were efficient catalysts for conjugate addition of carbon nucleophiles to nitroalkenes and sulfones, replacement of the C(9)-OH with an ester group (Q-7b) showed great improvement in stereoselectivity. The reaction is applicable to a variety of cyclic and acyclic enones (16,18). 

Chiral diester diamide macrocycles such as ll-180 have been synthesized (181) from esters of L-valine by, first of all, forming acyclic bisamides and then hydrolyzing the ester functions prior to template-promoted cyclization with cesium carbonate (182) and the appropriate dibromide. L-Tartaric acid has also been incorporated into a macrocycle, i.e., lll-181, of this type. 

Trost and his co-workers succeeded in the allylic alkylation of prochiral carbon-centered nucleophiles in the presence of Trost s ligand 118 and obtained the corresponding allylated compounds with an excellent enantioselec-tivity. A variety of prochiral carbon-centered nucleophiles such as / -keto esters, a-substituted ketones, and 3-aryl oxindoles are available for this asymmetric reaction (Scheme jg) Il3,ll3a-ll3g Q jjg recently, highly enantioselective allylation of acyclic ketones such as acetophenone derivatives has been reported by Hou and his co-workers, Trost and and Stoltz and Behenna - (Scheme 18-1). On the other hand, Ito and Kuwano... 

The synthesis of succinic acid derivatives, /3-alkoxy esters, and a,j3-unsaturated esters from olefins by palladium catalyzed carbonylation reactions in alcohol have been reported (24, 25, 26, 27), but full experimental details of the syntheses are incomplete and in most cases the yields of yS-alkoxy ester and diester products are low. A similar reaction employing stoichiometric amounts of palladium (II) has also been reported (28). In order to explore the scope of this reaction for the syntheses of yS-alkoxy esters and succinic acid derivatives, representative cyclic and acyclic olefins were carbonylated under these same conditions (Table I). The reactions were carried out in methanol at room temperature using catalytic amounts of palladium (II) chloride and stoichiometric amounts of copper (II) chloride under 2 atm of carbon monoxide. The methoxypalladation reaction of 1-pentene affords a good conversion (55% ) of olefin to methyl 3-methoxyhexanoate, the product of Markov-nikov addition. In the carbonylation of other 1-olefins, f3-methoxy methyl esters were obtained in high yields however, substitution of a methyl group on the double bond reduced the yield of ester markedly. For example, the carbonylation of 2-methyl-l-butene afforded < 10% yield of methyl 3-methyl-3-methoxypentanoate. This suggests that unsubstituted 1-olefins may be preferentially carbonylated in the presence of substituted 1-olefins or internal olefins. The reactivities of the olefins fall in the order RCH =CHo ]> ci -RCH=CHR > trans-RCH =CHR >... 

---