Unsaturated equivalents

Erythrogenic acid contains six degrees of unsaturation (see Sec. 6.2 for the method of calculating unsaturation equivalents for compounds containing elements other than C and H). 

The dithiastannoles 17-7 (the unsaturated equivalents of the dithiastannolanes that are mentioned above), have attracted attention because they can act as precursors for the tetrathiofulvalenes (17-8) which can show the properties of organic metals. The dithiastannoles can be prepared from the cyclic unsaturated dithiocarbonates as shown in equation 17-25, and then react with l,3-dithiole-2-carboxylates in the presence of Me3Al as catalyst to give the tetrathiofulvalenes (equation 17-26).38-40 Diselenadithiofulvalenes can be prepared in a similar way. 

The known stability of A -olefinic 5a-steroids compared with the A - or A -isomers is also a property of the unsubstituted frans-octalin system. cis-Octalins prefer A -unsaturation, equivalent to the favoured A -unsaturation in 5 -steroids. 

A complete listing of reactants, physical properties, and predicted and observed unsaturation equivalent weights for the telechelic (meth)acrylamide-functional oligomers is contained in Table 1. 

That all the measured unsaturation equivalent weight values exceed predicted values is an indication that some side reactions [vinyl polymerization of the Michael addition depicted in Equation (2)] may have occurred, but not to a significant amount. Based on the percentage difference between predicted and calculated values, these side reactions accounted for generally <10% reaction. 

Allylalion of the alkoxymalonitrile 231 followed by hydrolysis affords acyl cyanide, which is converted into the amide 232. Hence the reagent 231 can be used as an acyl anion equivalent[144]. Methoxy(phenylthio)acetonitrile is allylated with allylic carbonates or vinyloxiranes. After allylation. they are converted into esters or lactones. The intramolecular version using 233 has been applied to the synthesis of the macrolide 234[37]. The /i,7-unsaturated nitrile 235 is prepared by the reaction of allylic carbonate with trimethylsilyl cyanide[145]. 

The second largest use at 21% is for unsaturated polyester resins, which are the products of polycondensation reactions between molar equivalents of certain dicarboxyhc acids or thek anhydrides and glycols. One component, usually the diacid or anhydride, must be unsaturated. A vinyl monomer, usually styrene, is a diluent which later serves to fully cross-link the unsaturated portion of the polycondensate when a catalyst, usually a peroxide, is added. The diacids or anhydrides are usually phthahc anhydride, isophthahc acid, and maleic anhydride. Maleic anhydride provides the unsaturated bonds. The exact composition is adjusted to obtain the requked performance. Resins based on phthahc anhydride are used in boat hulls, tubs and spas, constmction, and synthetic marble surfaces. In most cases, the resins contain mineral or glass fibers that provide the requked stmctural strength. The market for the resins tends to be cychcal because products made from them sell far better in good economic times (see Polyesters,unsaturated). 

To analy2e fatty amines, both wet and instmmental methods of analysis are used. Wet methods routinely used are total amine value (ASTM Method D2073) combining weight or neutralization equivalent primary, secondary, and tertiary amine content (ASTM Method D2083) moisture, Kad-Fischer (ASTM Method D2072) and iodine value, measure of unsaturation (ASTM Method D2075). These provide important information on physical and chemical characteristics of the amine products used in various appHcation areas (8,76,81). In addition to the ASTM methods available, the American Oil Chemists Society has developed methods of analysis for fatty amines (82). 

Ethylene—Propylene Rubber. Ethylene and propjiene copolymerize to produce a wide range of elastomeric and thermoplastic products. Often a third monomer such dicyclopentadiene, hexadiene, or ethylene norbomene is incorporated at 2—12% into the polymer backbone and leads to the designation ethylene—propylene—diene monomer (EPDM) mbber (see Elastomers, synthetic-ethylene-propylene-diene rubber). The third monomer introduces sites of unsaturation that allow vulcanization by conventional sulfur cures. At high levels of third monomer it is possible to achieve cure rates that are equivalent to conventional mbbers such as SBR and PBD. Ethylene—propylene mbber (EPR) requires peroxide vulcanization. 

It is possible to monitor the reaction and determine the end point by the absence of an a,/S-unsaturated ketone absorption in the UV or by the determination of the consumption of ca. one molar equivalent of hydrogen peroxide by permanganate titration. 

P-Hydroxy-A-norpregn-3(5)-en-2-one (7) A solution of the hydroxy-methylene steroid (5) (24.8 g) dissolved in 240 ml of acetic acid and 240 ml of ethyl acetate is ozonized at — 10° with one molar equivalent of ozone. The resulting solution is diluted with 240 ml. of water and 60 ml of 30 % hydrogen peroxide and allowed to stand overnight. The solution is diluted with 1.5 liters of water and extracted with 3 x 700 ml portions of ethyl acetate. The combined extracts are washed with water, saturated sodium chloride solution, dried over sodium sulfate and concentrated to dryness under vacuum, leaving 23.4 g of a colorless amorphous residue of crude diacid. This material shows a maximum in the ultraviolet spectrum at 224 mp (s 6,400) indicating a 53 % yield of unsaturated acid (6). It is used without further purification. 

The first example of a cycloaddition reaction of a multiple bond to a diene was reported in 1917 Surprisingly, it was found that benzal azine adds to 2 equivalents of several unsaturated systems, when offered in excess, to yield bicyclie compounds. This reaction was named criss-cross" cycloaddition [190], Exploitation of the preparative potential of criss-cross cycloaddition began only in the early 1970s, when hexafluoroacetone azine became available on a larger scale [191,192] The study of this reaction proved to be an impetus tor the development of azine chemistry [183, 193]... 

This 1,3-migration of hydrogen was also observed when 40 reacted with Lawesson s reagent to produce the dithiolactone 41. However, when y-hydroxy-a,P-unsaturated aldehyde 42 was reacted under similar conditions, thiophene 43 was prepared efficiently. These results are not surprising considering that the oxidation state of 42 is equivalent to the traditional saturated 1,4-dicarbonyl substrates of the Paal thiophene reaction via tautomerization of the double bond, and aromaticity is reestablished in the fully conjugated 43. 

Van Leusen and co-workers also demonstrated the utility of dilithio-tosylmethyl isocyanide (dilithio-TosMIC) to extend the scope of the application. Dilithio-TosMIC is readily formed from TosMIC and two equivalents of n-butyllithium (BuLi) in THF at -70"C. Dilithio-TosMIC converts ethyl benzoate to oxazole 14 in 70% yield whereas TosMIC monoanion does not react. In addition, unsaturated, conjugated esters (15) react with dilithio-TosMIC exclusively through the ester carbonyl to provide oxazoles (16). On the other hand, use of the softer TosMIC-monoanion provides pyrroles through reaction of the carbon-carbon double bond in the Michael acceptor. 

Fully unsaturated azocines are 7r-equivalent heterocyclic analogs of cy-clooctatetraene. Addition of two electrons to the completely unsaturated azocine (34) can lead to a dianion 35 and removal of a proton from a dihy-droazocine (36) to the monoanion 37. Both the mono- and the dianions are lOTT-electron systems, corresponding to 7r-equivalent and 7r-excess analogs of cyclooctatetraenide [84CHEC-I(7)653], Aromatic dianions related to 35 have been fully characterized by and NMR (87TL2517). 

More recent work has shown that the 2-unsubstituted compound 40 (R = H, R = Pr ) is an effective formyl anion equivalent which reacts at C2 and undergoes both 1,4-addition to a,(3-unsaturated carbonyl compounds and 1,2-addition to aldehydes (93TL3907 96T4719). 

Although deprotonation of simple 1,3-dithiolanes at the 2 position is usually accompanied by cycloreversion to the alkene and dithiocarboxylate, this does not occur for the 2-ethoxycarbonyl compound 55. The anion of this is readily generated with LDA and undergoes conjugate addition to a,(3-unsaturated ketones, esters, and lactones to give, after deprotection, the a,8-diketoester products 56 (73TL2599). In this transformation 55 therefore acts as an equivalent of Et02C-C(0) . 

Among the most successful classes of asymmetric acyl anion equivalents are the dioxane-containing a-amino nitriles 99 introduced by Enders and coworkers. These are deprotonated by EDA, and the resulting anions act as efficient equivalents of RCO for addition to a, (3-unsaturated esters [90AG(E)179],... 

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