Poly functionalization reactions

PUR are a broad class of highly cross-linked plastics prepared by multiple additions of poly-functional hydroxyl or amino compounds. Typical reactants are polyisocyanates [toluene diisocyanate (TDI)] and polyhydroxyl molecules such as polyols, glycols, polyesters, and polyethers. The cyanate group can also combine with water this reaction is the basis for hardening of the one-part foam formulations. 

Functionalized organozinc halides are best prepared by direct insertion of zinc dust into alkyl iodides. The insertion reaction is usually performed by addition of a concentrated solution (approx. 3 M) of the alkyl iodide in THF to a suspension of zinc dust activated with a few mol% of 1,2-dibromoethane and MeaSiCl [7]. Primary alkyl iodides react at 40 °C under these conditions, whereas secondary alkyl iodides undergo the zinc insertion process even at room temperature, while allylic bromides and benzylic bromides react under still milder conditions (0 °C to 10 °C). The amount of Wurtz homocoupling products is usually limited, but increases with increased electron density in benzylic or allylic moieties [45]. A range of poly-functional organozinc compounds, such as 69-72, can be prepared under these conditions (Scheme 2.23) [41]. 

In principle, bifunctional aldehydes should be able to engage in twofold enzymatic aldol additions to both of their acceptor carbonyls in a fashion to be classified as a tandem reaction, that is, without the need for isolation of intermediates. Depending on the specificity of the enzyme used and on the functionalization in the starting material, the isomeric constitution as well as the absolute and relative stereochemistry should be deliberately addressable. Therefore, we engaged in a program to evaluate the scope and the Hmitations of such two-directional chain elongation processes for the construction of extended poly functional molecules [36]. 

Alkyd. Alkyd resins are the reaction product of a poly functional alcohol and a polyfunctional acid. When the resin is combined with a filler, catalyst, pigment, and release agent the resultant product is a granular or putty or rope-type molding compound. Fillers used may be fine mineral, glass, mineral and nylon—depending on the end product desired. 

The carbonation of polymeric anions using carbon dioxide is one of the most useful and widely used functionalization reactions. However, there are special problems associated with the carbonation of polymeric organolithium compounds317 . For example, Wyman, Allen and Altares318) reported that the carbonation of poly-(styryl)lithium in benzene with gaseous carbon dioxide produced only a 60% yield of carboxylic acid the acid was contaminated with significant amounts of the corresponding ketone(dimer) and tertiary alcohol(trimer) as shown in Eq. (70). 

The use of a reactive di- or poly-functional comonomer (non-antioxidant) which can co-graft with a monofunctional polymerisable antioxidant on polymers can improve the grafting efficiency from as low as 10-40% to an excess of 80-90%. This strategy, however, presents immense challenges due to the presence of more than one polymerisable group in the comonomer which could lead to additional undesirable (competing) side reactions com-... 

More recently, Porta and co-workers [6] applied similar considerations of the polar effects to a new one-pot multicomponent process for the addition of nucleophilic radicals to aldimines, generated in situ in the presence of Ti(IV). In analogy with the Minisci reaction, Ti(IV), which acts as a Lewis acid, coordinates the nitrogen of the imine, strongly increasing the electron-deficient character of the carbon in the a-posilion and thus the reactivity of the imine toward nucleophilic radicals. This reaction, as well as the Minisci one, represents a useful route for the synthesis of a variety of poly-functionalized derivatives of chemical and biochemical relevance. 

Whereas cyclic SisPhio can be selectively mono- and difunctionalized by triflic acid66 (equation 38), the reaction of S Phs always yields mixtures of mono- and poly-functionalized products67. The introduction of the more reactive p-tolyl substituents in [SiPh(p-Tol)]4 (four stereoisomers possible) results in a selective monofunctionalization but the products consist of all six possible stereoisomers68 (equation 39). 

Thus, by variation of the ketone, olefin, and catalyst these reactions can be utilized for the synthesis of a wide variety of poly functional long-chain molecules.1073 b... 

Many combinations of substituents at the cyclopropane ring have been realized, but not all are of synthetic value. In this respect alkyl 2-siloxycyclopropanecarboxylates are of particular versatility. They allow many modes of ring cleavages which can be combined with change of functionality or with C-C-bond forming reactions providing a manifold of poly functional 1,4-dicarbonyl compounds, carbocycles, and heterocyclic systems as products. 

A typical example of a condensation polymerization reaction is the reaction between a poly functional alcohol (e.g. a glycol) and a dicarboxylic acid (e.g. terephthalic acid). 

A slightly modified version of the same reaction allowed the synthesis of poly-functionalized a-diketones from linear enamino ketones23 (Scheme 8). 

While catalysts are also used in the production of other types of polymers, the properties of most of these materials are not particularly dependent on the type of catalyst employed. Many poly condensation reactions, e. g. the formation of polyesters, polyamides or urea-formaldehyde resins, are speeded up by addition of some Bronsted or Lewis acids. Since relevant properties of these polymer products, such as their average chain lengths, are controlled by equilibrium parameters, primarily by the reaction temperatures and molar ratios of the monomers employed, and since their linkage patterns are dictated by the functional groups involved, addition of a catalyst has little leverage on the properties of the resulting polymer materials. 

The replacement reaetion by poly functional nitrogen-containing derivatives, in particular, makes it possible to introduce multiple RCH2 groups into the same molecule. Thus, the reaction of indole Mannich bases with ammonia y ields bis- and tris-(3-indolyl) amines. Likewise, primary amines, hydrazine, and hydroxylamine can be bis-alkylated by several Mannich bases. 

Most of the poly functional substrates belonging to this group of compounds have two (or more) active hydrogen atoms located on different positions of the molecule. Thus, in the case of symmetrical substrate with two identical reactive XH groups 109, the Mannich bases 110-115 (Rg. 42) arc obtained by reaction of the. substrate with formaldehyde and amine in the molar ratio 123. 

Various derivatives of fiuan and pyran are cleaved to give open-chain di- and poly-functional compounds. Fission to give dihalides, halo alcohols, and halo esters is described elsewhere (method 34). Hydrogenation and hydrogenolysis reactions lead to hydroxy compounds, as in the preparation of 5-hydroxy-2-pentanone and 1,4-pentanediol from methyl-... 

When poly(ethylene glycol) of molecular weight 1000 was used as the starting material for this poly addition reaction, polymers of molecular weight more than 20000 were obtained. As the functional groups are located in equidistant order, neighbouring effects can be excluded in this copolymer. 

The synthetic potential of these reactions can be illustrated by their use for the construction of poly-functionalized cyclopentanecarboxylic acids and derivatives (Scheme 25). The Michael-induced... 

The anti diols are obtained in a stereoselective manner by reaction with Me4N(AcO)3BH in MeCN-AcOH [ECl, EC2, LYl] (Figure 3.37). The reduction takes place by an intramolecular hydride delivery via the least hindered chairlike transition state 3.110 (Figure 3.37). These methods are compatible with functional groups such as esters or amides. For instance, from poly functional -hydroxyketone 3.111, either diastereoisomeric diol is obtained with a high selectivity [EG2]. In some cases, NalAcOl BH can be used instead of the ammonium salt. 

Similarly, poly(dimethylsiloxane) (pDMS), an inorganic polymer, has been incorporated into block copolymers using a functionalization reaction. Maty-jaszewski et al. used commercially available hydrosilyl or vinylsilyl terminated... 

Finally, a novel three-component radical cascade reaction involving isonitriles has just been published [6]. In this paper, aromatic disulfides, alkynes, and isonitriles have been reported to react under photolytic conditions to afford -arylthio-substituted acrylamides 49 or acrylonitriles 50 in fair yields as mixtures of the E and Z geometric isomers (Scheme 21). The procedure entails addition of a sulfanyl radical to the alkyne followed by attack of the resulting vinyl radical on the isonitrile. A fast reaction, for example, scavenging by a nitro-derivative (route a) or f-fragmentation (route b), is necessary in order to trap the final imidoyl radical, since addition of vinyl radicals to isonitriles seems to be a reversible process. The reaction provides very easy access to potentially useful poly-functionalized alkenes through a very selective tandem addition sequence. 

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