1.3- Pentadiene acidity

Perchloro-2,4-pentadienic acid pyrrolidide heated 3 hrs. at 160° 3,4,5,6-tetra-... 

Another protecting group of amines is 1-isopropylallyloxycarbonyl, which can be deprotected by decarboxylation and a /3-elimination reaction of the (tt-l-isopropylallyl)palladium intermediate under neutral conditions, generating CO2 and 4-methyl-1,3-pentadiene. The method can be applied to the amino acid 674 and peptides without racemization[437]. 

The l,5-hexadien-3-ol derivatives 792 and 794 are cycli2ed to form the cyclo-pentadiene derivatives 793 and 795 by insertion of an alkene into -allylpalla-dium formed from allylic alcohols in the presence of trifluoroacetic acid (lO mol%) in AcOH[490],... 

The same anion is formed by loss of the most acidic proton from 1 methyl 1 3 cyclo pentadiene as from 5 methyl 1 3 cyclopentadiene Explain... 

Compound 95, a 5-chloro-2,4-pentadien-l-one is a doubly vinylog-ous acid chloride. The addition of j8-chlorovinyl ketones to acetylenes was known to afford such compounds as 95 366,867 valence... 

El-3-r/ ethyl-1,3-pentadiene (E)-1 -Bromo-2-isopropyl-1,3-butadiene (Z)-2-Hydroxymethyl-2-butenoic acid... 

Isophthalic acid, 2-hydroxy-, 40,48 Isoprene, addition to dichlorophenyl-phosphine, 43, 73 Isopropyl isocyanide, 41,14 5 Isopropyl-1,2,3,4,5-pen tachlorocyclo-pentadiene, 43, 92... 

Malonic acid, amino-, diethyl ester, HYDROCHLORIDE, 40, 24 Malonic acid, bts(hydroxymethyl)-, DIETHYL ETHER, 40, 27 Malonitrile, condensation with tetra-cyanoethylene, 41, 99 2-Mercaptopyrimidine, 43, 6S hydrochloride of, 43, 68 Mercuric oxide in preparation of bromo-cyclopropane, 43, 9 Mesityl isocyanide, 41,103 5-Methallyl-l,2,3,4,5-pentachlorocyclo-pentadiene, 43, 92 Methane, dimesityl-, 43, 57 Methanesiileinyl chloride, 40, 62 Methanesulfonic acid, solvent for making peroxybenzoic acid from benzoic acid, 43, 93... 

Pentachloro-5-ethylcyclo-pentadiene, 43, 90 Pentacyanopropenc, 41,100 acid strength of, 41, 100 Pentane, 2,2,4-trim ethyl-4-nitro, 43, 87... 

C-Disaccharide analogs of trehalose were recently [20c] prepared by using as a key step an aqueous Diels-Alder reaction between the sodium salt of glyoxylic acid and the water soluble homochiral glucopyranosil-l,3-pentadiene 19 (Equation 6.1). A mixture of four diastereoisomers in a 41 24 21 14 proportion was obtained after esterification with methanol and acetylation. The main diaster-eoisomer 20 was isolated and characterized as benzoyl-derivative. 

Recently, a more detailed study of this system has been carried out, together with the behavior of 3,4-pentadien-l-yl iodide, 157 (149), a system which has previously been shown to solvolyze through ion 156 (87,91). The products of reaction of 154-1 and 157 with AgOAc in acetic acid at 25° C are given in Table VIII. The similarity of the products and their relative amounts... 

H-Pyran-2-iminium salts (2) are formed by the acid-catalysed cyclisation of the pentadienal (1), itself accessible from the addition of HCl to 5-dimethylaminopenta-2-en-4-ynal, a push-pull enyne <96HCA192>. 

It was also shown that a cahonic allylnickel complex [(q3-crotyl)Ni P(OEt)3 2]PF6 catalyzes this reaction without added acid and that ds- and trans-1,3-pentadienes react with morpholine to give a mixture of 1,2- and 1,4-addition products [178]. 

Diethoxyphosphoryloxy)-1,3-butadiene and 2-(diethoxyphosphoryloxy)-1,3-pentadiene are good dienes and are compatible with Lewis acid catalysts.50 They exhibit the regioselectivity expected for a donor substituent and show a preference for endo addition with enones. 

Lipoxygenases, which catalyse the oxidation of unsaturated fatty acids containing the cis,cis-l,4-pentadiene moiety to the corresponding 1 -hydroperoxy-f rans,ds-2,4-diene (Table 2.3), are widely distributed in plants and animals. The mammalian... 

The 2,5-dihydro-l,2-oxaphosphole-2-oxide derivatives 196 were also obtained from the reaction of esters of 3-chloro-4-methyl-l,3-pentadiene-2-phosphonic acid with halogens (Scheme 78) [155, 156],... 

The biosynthetic origin of the depolymerization-resistant core of cutin (cutan) remains to be established. The early observation that linoleic acid and linolenic acid were preferentially incorporated into the non-depolymerizable core of cutin in apple skin slices suggested that the ether-linked or C-C-linked core might arise preferentially from the czs-l,4-pentadiene system [31]. The insoluble residue, that contained the label from the incorporated polyunsaturated C18 acids, released the label upon treatment with HI, supporting the notion that some of those aliphatic chains were held together by ether bonds. More recently,... 

Complexes 17-19 can be written in one valence structure as a, /3-unsaturated carbonyl compounds in which the carbonyl oxygen atom is coordinated to a BF2(OR) Lewis acid. The C=C double bonds of such organic systems are activated toward certain reactions, like Diels-Alder additions, and complexes 17-19 show similar chemistry. Complexes 17 and 18 undergo Diels-Alder additions with isoprene, 2,3-dimethyl-1,3-butadiene, tram-2-methyl-l,3-pentadiene, and cyclopentadiene to give Diels-Alder products 20-23 as shown in Scheme 1 for complex 17 (32). Compounds 20-23 are prepared in crude product yields of 75-98% and are isolated as analytically pure solids in yields of 16-66%. The X-ray structure of the isoprene product 20 has been determined and the ORTEP diagram (shown in Fig. 3) reveals the regiochemistry of the Diels-Alder addition. The C-14=C-15 double bond distance is 1.327(4) A, and the... 

For the synthesis of permethric acid esters 16 from l,l-dichloro-4-methyl-l,3-pentadiene and of chrysanthemic acid esters from 2,5-dimethyl-2,4-hexadienes, it seems that the yields are less sensitive to the choice of the catalyst 72 77). It is evident, however, that Rh2(OOCCF3)4 is again less efficient than other rhodium acetates. The influence of the alkyl group of the diazoacetate on the yields is only marginal for the chrysanthemic acid esters, but the yield of permethric acid esters 16 varies in a catalyst-dependent non-predictable way when methyl, ethyl, n-butyl or f-butyl diazoacetate are used77). 

A striking example for the preferred formation of the thermodynamically less stable cyclopropane is furnished by the homoallylie halides 37, which are cyclopro-panated with high c/s-selectivity in the presence of copper chelate 3891 The cyclopropane can easily be converted into cw-permethric acid. In contrast, the direct synthesis of permethric esters by cyclopropanation of l,l-dichloro-4-methyl-l,3-pentadiene using the same catalyst produces the frans-permethric ester (trans-39) preferentially in a similar fashion, mainly trans-chrysanthemic ester (trans-40) was obtained when starting with 2,5-dimethyl-2,4-hexadiene 92). 

The change in selectivity is not credited to the catalyst alone In general, the bulkier the alkyl residue of the diazoacetate is, the more of the m-permethric acid ester results 77). Alternatively, cyclopropanation of 2,5-dimethyl-2,4-hexadiene instead of l,l-dichloro-4-methyl-l,3-pentadiene leads to a preference for the thermodynamically favored trans-chrysanthemic add ester for most eatalyst/alkyl diazoacetate combinations77 . The reasons for these discrepandes are not yet clear, the interplay between steric, electronic and lipophilic factors is considered to determine the stereochemical outcome of an individual reaction77 . This seems to be true also for the cyclopropanation of isoprene with different combinations of alkyl diazoacetates and rhodium catalysts77 . 

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