Subject cyclic carbonates

The coupling product 177 is subjected to epoxidation to give epoxide compound 178 on which the C-l hydroxyl group will be generated via catalytic hydrogenation. After the dihydroxyl groups of the hydrogenation product 179 have been protected with cyclic carbonate, the C=C double bond between C-l2... 

In this chapter the processes used for the synthesis of either acyclic or cyclic carbonates, as alternatives to the use of phosgene, will be considered. Details of both the rich patent and scientific literature that is appropriate to the subject will also be included. 

Since oxiranes are representative heterocyclic monomers containing an endo-cyclic heteroatom, and the most commonly polymerised of such monomers, they have been subjected to copolymerisations with heterocyclic monomers containing both an endocyclic and an exocyclic heteroatom. Coordination copolymerisations of heterocyclic monomers with different functions are focused on oxirane copolymerisation with cyclic dicarboxylic acid anhydride and cyclic carbonate. However, the statistical copolymerisation of heterocyclic monomers with an endocyclic heteroatom and monomers with both endocyclic and exocyclic heteroatoms have only a limited importance. Also, the block copolymerisation of oxirane with lactone or cyclic dicarboxylic acid anhydride is of interest both from the synthetic and from the mechanistic point of view. Block copolymerisation deserves special interest in terms of the exceptionally wide potential utility of block copolymers obtained from comonomers with various functions. It should be noted, however, that the variety of comonomers that might be subjected to a random, alternating and block polymerisation involving a nucleophilic attack on the coordinating monomer is rather small. 

Hofmann-Loffler-Freytag reaction Derivatization by the title reagent (prepared from 2,2,2-trifluoroethylamine and phosgene) transforms an alcohol into a N- 2,2,2-trifluoroethyl)carbamate, which on subjecting to a Hofmann-Loffler-Ereytag reaction delivers the cyclic carbonate of a 1,3-diol. 

There are a number of heterocyclic monomers, for example, epoxides, cyclic sulfides, lactones and lactides, lactams, cyclic carbonates, and cydosUoxanes, which can be polymerized by ring-opening reactions many of them can he polymerized by an anionic as well as by a cationic mechanism. They cannot all be covered here, but there are a number of monographs and reviews on this subject [181-185]. 

Thus, when 2,2-dimethyl-, 2-methyl-2-n-propyl- and 2-methyl-2-iso-amylpropane-l,3-diol were treated with diethyl carbonate in the presence of catalytic amounts of sodium methoxide, only PCs were produced in high yield. On the other hand, six-membered cyclic carbonates are exclusively produced when 2,2-diethyl-, 2-ethyl-2-phenylpropane-1,3-diol, pentane-2,4-diol, 2-methylpentane-2,4-diol, and butane-1,3-diol were subjected to the transesterification reaction (Scheme 10). 

Similarly, cyclobis(hexamethylene carbonate), a dimer of nine-membered cyclic carbonate, was subjected to polymerization in bulk at 140 °C using BuSnCls or Sn(Oct)2 as a catalyst. The best results were obtained with BuSnCls affording polymer yields up to 89% and weight-average molecular weight of Af w = 200 000. In all cases the Af /Af n ratio was of the order of 2. DSC measurements showed that the PC rapidly crystallizes even at a cooling rate of 40 ° C min". ... 

In this study we examine the generalities in reductive alkylation however, since the subject is vast, we limited ourselves to the interaction of aromatic and aliphatic primary amines and diamines with ketones. The ketones examined include the cyclic ketone, cyclohexanone, and aliphatic ketones such as acetone, and methyl isobutyl ketone (MIBK). We limited our study to sulfided and unsulfided Pt and Pd catalysts supported on activated carbon that were commercially available from Evonik Degussa Corporation. 

The subjects of this section are two reactions that do not actually involve carbo-cation intermediates. They do, however, result in carbon to carbon rearrangements that are structurally similar to the pinacol rearrangement. In both reactions cyclic intermediates are formed, at least under some circumstances. In the Favorskii rearrangement, an a-halo ketone rearranges to a carboxylic acid or ester. In the Ramberg-Backlund reaction, an a-halo sulfone gives an alkene. 

Aldol addition and related reactions of enolates and enolate equivalents are the subject of the first part of Chapter 2. These reactions provide powerful methods for controlling the stereochemistry in reactions that form hydroxyl- and methyl-substituted structures, such as those found in many antibiotics. We will see how the choice of the nucleophile, the other reagents (such as Lewis acids), and adjustment of reaction conditions can be used to control stereochemistry. We discuss the role of open, cyclic, and chelated transition structures in determining stereochemistry, and will also see how chiral auxiliaries and chiral catalysts can control the enantiose-lectivity of these reactions. Intramolecular aldol reactions, including the Robinson annulation are discussed. Other reactions included in Chapter 2 include Mannich, carbon acylation, and olefination reactions. The reactivity of other carbon nucleophiles including phosphonium ylides, phosphonate carbanions, sulfone anions, sulfonium ylides, and sulfoxonium ylides are also considered. 

Since model compounds reveal well-defined cyclic voltammograms for the Cr(CNR)g and Ni(CNR)g complexes (21) the origin of the electroinactivity of the polymers is not obvious. A possible explanation (12) is that the ohmic resistance across the interface between the electrode and polymer, due to the absence of ions within the polymer, renders the potentially electroactive groups electrochemically inert, assuming the absence of an electronic conduction path. It is also important to consider that the nature of the electrode surface may influence the type of polymer film obtained. A recent observation which bears on these points is that when one starts with the chromium polymer in the [Cr(CN-[P])6] + state, an electroactive polymer film may be obtained on a glassy carbon electrode. This will constitute the subject of a future paper. 

Oxidative attack on a carbon-hydrogen bond of an alkyl group a to a nitrogen atom is not restricted to saturated aliphatic amines. In fact X in an X-N-CH- structural subunit can be virtually any common atomic grouping that can be found in stable organic molecules. For example, w-carbon hydrogens of Aralkyl-substituted aromatic cyclic amines (119), aryl amines (120), amides (121), amidines (122), A-nitrosodialkylamines (123), etc. are all subject to oxidative attack, carbinolamine formation, and in most cases release of an aldehyde or ketone depending on the substitution pattern (1° or 2°)... 

The cationic ring-opening polymerization of cyclic ethers has been the subject of many recent investigations (1.. Nuclear magnetic resonance (NMR) methods, particularly carbon-13 techniques, have been found most useful in studying the mechanism of these polymerizations ( ). In the present review we would like to report some of our recent work in this field. 

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