Nitrile reaction summary

The as-spun acrylic fibers must be thermally stabilized in order to preserve the molecular structure generated as the fibers are drawn. This is typically performed in air at temperatures between 200 and 400°C [8]. Control of the heating rate is essential, since the stabilization reactions are highly exothermic. Therefore, the time required to adequately stabilize PAN fibers can be several hours, but will depend on the size of the fibers, as well as on the composition of the oxidizing atmosphere. Their are numerous reactions that occur during this stabilization process, including oxidation, nitrile cyclization, and saturated carbon bond dehydration [7]. A summary of several fimctional groups which appear in stabilized PAN fiber can be seen in Fig. 3. 

In summary, these exploratory data suggest that the chromatographic method used could be a valuable tool for study of this polymerization reaction. Reasonable data were obtained for amount and composition of the copolymer. Formation of graft polymer and/or nitrile rich polymer was detected. More detailed chromatographic study of this batch polymerization could lead to a practical on-line monitoring method... 

In summary, reactions of nitronates with acid anhydrides or acyl chlorides give the O-acylated products, and reactions with acyl imidazoles, phenyl esters, acyl nitriles, and enol-lactones gives the C-acylated products, (see Eq. 5.13).25 The C/O selectivity of nitronate acylation by RCOX is qualitatively correlated with strength (pKJ of the acid HX conjugated to the leaving group X .25... 

In summary, the formation of optically active compounds through hydrolysis reactions is dominated by biocatalysis mainly due to the availability and ease of use of a wide variety of esterases, lipases and (to a lesser extent) acylases. Epoxide ring-opening (and related reactions) is likely to be dominated by salen-metal catalysts while enzyme-catalysed nitrile hydrolysis seems destined to remain under-exploited until nitrilases or nitrile hydratases become commercially available. 

In summary, (R)-phenylglycine amide 1 is an excellent chiral auxiliary in the asymmetric Strecker reaction with pivaldehyde or 3,4-dimethoxyphenylacetone. Nearly diastereomerically pure amino nitriles can be obtained via a crystallization-induced asymmetric transformation in water or water/methanol. This practical one-pot asymmetric Strecker synthesis of (R,S)-3 in water leads to the straightforward synthesis of (S)-tert-leucine 7. Because (S)-phenylglycine amide is also available, this can be used if the other enantiomer of a target molecule is required. More examples are currently under investigation to extend the scope of this procedure. ... 

In Section IV-VI we systematically discuss the acidity, basicity and, where appropriate, the hydrogen-bonding of nitrones, nitriles and thiocarbonyls. Since this review very much relies on physical measurements and the discussion of acid-base reactions, Section HI provides a brief introduction to proton affinity and a short summary of the acid-base concept and the quantitative measure of basicity. 

Amines can be prepared by reduction of nitro compounds, nitriles, and amides. Because the details of these reactions have been discussed previously, they are presented here in summary form only. 

Summary The thermally stable silylene Si[ N(CH2tBu) 2C6H4-l,2] 1 readily undergoes addition reactions with compounds containing CO and CN multiple bonds (e g., ketones, imines, nitriles or isonitriles). The products, most of them characterized by their X-ray structures, contain novel skeletal frameworks SiCOSi, SiOSiCCC, SiCNSi, CSi(CN),... 

The reactions of 17a with nitriles have been examined extensively and have been shown (by nmr), in many cases, to proceed quantitatively in liquid S02. Yields are commonly in excess of 80%. A summary of all published reactions of this type is given in Table IX. In the majority of cases, reaction proceeds smoothly at room temperature over 1-24 h. 

The most extensively studied reaction of 1,2,4-triazines is the Diels-Alder reaction with inverse electron demand, in which the triazines behave as reactive electron-deficient dienes. Electron-rich alkenes and acetylenes have been most often used as dienophiles but alkenes with strained double bonds and nitriles can also react. Besides intermolecular Diels-Alder reactions, which were discussed in detail in CHEC-I, intramolecular cycloadditions have been studied widely and used in the synthesis of condensed heterocyclic systems. A review on intermolecular Diels-Alder reactions was published by Roger and Weinreb in 1987 , Sauer published an account of his studies in 1992 <92BSB52l>, and a summary by Taylor of his own work on intramolecular Diels-Alder reactions was published in 1988 <88BSB599>. 

Intramolecular asymmetric Stetter reactions enjoy a range of acceptable Michael acceptors and acyl anion precursors. These reactions can utilize aromatic, heteroaromatic, and aliphatic aldehydes with a tethered a,p-unsaturated ester, ketone, thioester, malonate, nitrile, or Weinreb amide. In this part, we will give a brief summary about asymmetric intramolecular Stetter reactions and selected recent results in this area (Scheme 7.17). 

Many other functional groups are also reactive under conditions of catalytic hydrogenation. The reduction of nitro compounds to amines, for example, usually proceeds very rapidly. Ketones, aldehydes, and esters can all be reduced to alcohols, but in most cases these reactions are slower than alkene reductions. For most synthetic applications, the hydride transfer reagents to be discussed in Section 5.2 are used for reduction of carbonyl groups. Amides and nitriles can be reduced to amines. Hydrogenation of amides requires extreme conditions and is seldom used in synthesis, but reduction of nitriles is quite useful. Scheme 5.3 gives a summary of the approximate conditions for catalytic reduction of some common functional groups. 

The reaction of a-keto acids with nitriles in the presence of acid catalysts has also been frequently applied to the preparation of acylaminoacrylic acid derivatives 150, 318, 369). a-Acylaminoacrylic acids are obtained directly from a-halonitriles and excess keto acid under rigorous exclusion of moisture. If the reaction is conducted in the presence of water and excess nitrile, a,a-bis-acetylamino carboxylic acids are formed in very good yields, and can be converted into the acylaminoacrylic acids in a subsequent step. The summary by Greenstein and Winitz 150) should be consulted for more detailed information. 

Several recent review articles provide excellent summaries of the stoichiometric and catalytic reactivity of synthetic metal aqua and hydroxide complexes with carbon-centered electrophiles (esters, amides, peptides, CO2, nitriles) [8, 10-13, 82-90] and phosphate derivatives (activated phosphate esters, DNA, RNA) [6, 11-13, 17-20, 82, 83, 85, 91-99]. In particular, these reviews provide insight into how various metal/ligand assemblies influence catalytic hydrolytic reactions. 

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