Double chains

Stigmasterol from soy bean extracts can be selectively ozonolyzed on the side-chain double bond. The 20-formyl group formed is converted to the enamine with piperidine. This can be oxidized to progesterone. 

Hydrogenation of the side chain double bond of an alkenylbenzene is much easier than hydrogenation of the aromatic ring and can be achieved with high selectivity leav mg the ring unaffected... 

Polymerisation of conjugated dienes can frequently lead to the formation of linear polymers containing main chain double bonds. Examples of such diene... 

Because the polybutadiene component is liable to oxidation, ABS materials are embrittled on prolonged exposure to sunlight. By replacing polybutadiene rubber with other elastomers that contain no main chain double bonds it has been possible to produce blends generally similar to ABS but with improved weathering resistance. Three particular types that have achieved commercial status are ... 

If, however, radicals add preferentially to the vinyl group of 48, ring-opening polymerization w-ould give the polymer with in-chain double bonds specifically via resonance structure 49 (Scheme 4.31). Thus, the two pathways are readily distinguishable. No other ring-opening polymerizations of vinyl dioxolane derivatives appear to have been reported to date. 

Vinyl- and 3-vinylthiophene (73b and 77) are less reactive than the corresponding furans and show a notable preference for extra-annular addition due to the higher reactivity of the diene system, including the side-chain double bond. 2-Vinylthiophene is less reactive than 3-vinylthiophene. Whereas 2-vinylthiophene (73b) reacted with maleic anhydride and 1,4-benzoquinone to give cycloadducts in reasonable yield, 3-vinylthiophene (77) gave a higher yield of the cycloadduct [76, 77] (Scheme 2.31). 

An efficient template-guided polycondensation of a decadeoxynucleotide into long-chain double-stranded polydeoxynucleotides was achieved with the thymidine 3 -phos-phoric imidazolides [161]... 

Chain Double bond position, counting from the functional group... 

Diazaquinones 68, 83a, and 90 have been shown to provide adducts with various isoprenoids, as exemplified by the /3-myrcene adduct 140 (87H193). The side-chain double bonds of these adducts can be functionalized by epoxidation with 3-chloroperoxybenzoic acid or via bromination with IV-bromosuccinimide to provide the corresponding derivatives 141 and 142, respectively (Scheme 34). 

In the cyclocondensation of diethyl acetylmalonate and 4-alkylamino-1,5-benzodiazepines (1411) in benzene in the presence of acetic acid and piperidine, the addition of acetylmalonate at the side-chain double bond of 1411 took place first. The amino group at position 4 was involved only in the second step of the reaction sequence to give tricyclic derivatives (1412) in 49-77% yields (85FES391). 

Drawing a carbon-atom chain. Double and triple bonds. Clearing the screen... 

Figure 2.3 Some examples of chain composite building units, (a) Single chain (zig-zag) and (b) double chain (double zig-zag) with periodicities of two. (c) Single chain (crankshaft) and (d) double chain (double crankshaft) with periodicities of four, (e) Complex chain (designated mod by Smith...

Fig. 2.1 Configurations of the tetrahedral units and chain, double chain, and sheet structures in the silicate and aluminosilicate minerals. (A) Two-dimensional representation of a single silicate tetrahedron. (A ) Two-dimensional representation of an extended silicate chain. (B) Three-dimensional representations of single tetra-hedra in two orientations. The apexes of the tetrahedra point above or below the plane of the paper. (B ) Three-dimensional representations of extended silicate chains showing different orientations of the tetrahedra in two of the many possible configurations. Single chain pyroxenes (C), wollastonite (D), rhodonite (E). Double chains amphiboles (F). Sheets as found in the serpentines, micas, and clays (G).

The most abundant of the isolated amides was fagaramide (JL). The structure of fagaramide has long been known,but the geometry of its side chain double bond has not been clearly established. This has now been confirmed as trans based on the large coupling constant (16 Hz) in the 400 MHz H-NMR spectrum. 

Through a comparison of the activities of the nine natural and synthetic compounds in Table I, certain functionalities appeared to be important in the efficacy of the isobutylamides to inhibit the growth of the lepidopterous larvae. These functionalities included the chain length, presence of the methylenedioxy moiety, the number of the side chain double bonds, and the stereochemistry of the side chain. Combinations of these functionalities would likely enhance the activity. For instance, Miyakado et al.H found that addition of the methylenedioxy moiety to pellitorine (4) increased its toxicity when topically applied to adults of the beetle, Callosobruchus chinensis. 

Quinoline homologs and derivatives, including those with double bonds in the side chains, were reduced selectively by catalytic hydrogenation over platinum oxide (side chain double bonds), and to dihydro- and tetrahydro-quinolines by sodium in butanol, by zinc and formic acid, and by triethylam-monium formate [319, 472]. Catalytic hydrogenation of quinoline and its derivatives has been thoroughly reviewed [439]. 

Apart from the conversion of peroxides to useful products, it is sometimes necessary to reduce peroxides, and especially hydroperoxides formed by auto-oxidation. Such compounds are formed especially in hydrocarbons containing branched chains, double bonds or aromatic rings, and in ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, etc. Since most peroxidic compounds decompose violently at higher temperatures and could cause explosion and fire it is necessary to remove them from liquids they contaminate. Water-immiscible liquids can be stripped of peroxides by shaking with an aqueous solution of sodium sulfite or ferrous sulfate. A simple and efficient way of removing peroxides is treatment of the contaminated compounds with 0.4 nm molecular sieves [669]. 

Tactic polymer in which the main-chain double bonds of the configurational base units are entirely in the Z configuration. 

The position and geometry of the side chain double bonds can be determined by ozonolysis and a potassium permanganate-sodium periodate oxidation, as well as by the IR spectrum. Results have shown that the side chain double bonds are always Z 16,122,126). 

For the reaction of 1,3-dioxin -ones with electrophiles, activation by deprotonation of the side-chain alkyl group is required. Typically lithium diisopropylamide (LDA) is used as a base. The resulting lithium dienolates react with aldehydes <2002EJ0718> or with allyl bromides in the presence of Ar,Ar -dimethylpropyleneurea (DMPU) <2005AGE820, 2006CEJ2488> exclusively at the side-chain double bond, albeit in modest yields (Equation 25). 

NOED spectroscopy was used to determine the configurations of the four conjugated side-chain double bonds in some retinoids and their methoxy derivatives, for example 4. Arrows indicate NOE perturbances directed from the irradiated proton(s) towards those which show an NOE response280. Analogously, the configuration of C-5 in carboprostacyclin 5 was determined281. 

The hydrolysis products from the hypothetical Si4+ ion are the many and varied polymeric silicate ions which exist as chains, double chains, and sheets, culminating in the insoluble neutral three-dimensional arrays with the formula SiC>2. 

Thermolysis of the (Z)-acraldehyde 265 gives a mixture of the pyridyl-pyrazoles 266 and 267.258 From the (JS )-acraldehyde only compound 266 was obtained. In this reaction the diazoalkane is presumably trapped by the side-chain double bond, with subsequent formyl migration. 

Basically, COCs can be manufactured by ring opening metathesis polymerization (ROMP) as described in the chapter about metathesis polymers. However, ROMP offers disadvantages as main chain double bonds must be hydrated after polymerization. Therefore, COCs are more conveniently straightforwardly prepared by addition polymerization. 

However, the presence of defects such as loops, pendant chains, double connections, cannot be excluded. The former are more likely to occur when the polymer concentration of the reaction medium is low, the latter when it is very high. The... 

Because each chiral center added to a chain doubles the number of possible configurations, we expect eight different stereoisomers with three chiral carbons, sixteen with four, and so on. The simple rule then is 2n possible different stereoisomers for n chiral centers. As we shall see later, this rule has to be modified in some special cases. 

The sterols that were chosen as substrates contained two double bonds, one at various positions in the side chain and A5 in the steroid nucleus. Whereas the latter double bond was never touched in reactions with the Fe(III) porphyrin vesicle system 183 in the presence of PhIO, the side chain double bonds of desmosterol 186 and fucosterol 187 were epoxidized to 188 and 189 in 32% and 22% yield, respectively (Fig. 31). In contrast, stigmasterol 190 was not reactive, since the double bond cannot approach the reactive iron-oxo intermediate. 

Fibroin, the fibrous protein found in silk, has a secondary structure called a beta- (/8-) pleated sheet, in which a polypeptide chain doubles back on itself after a hairpin bend. The two sections of the chain on either side of the bend line up in a parallel arrangement held together by hydrogen bonds (Figure 24.8). Although not as common as the a-helix, small pleated-sheet regions are often found in proteins. 

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