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Isopropenyl group

The intermediate isopropenyl group can be removed with I2 (NaHC03, THF, H2O, rt, 78% yield). [Pg.213]

Although the initial monomer concentration was very high (25-200 g/1), soluble polymers were obtained even after complete conversion of DIPB. The measurements of the content of pendant isopropenyl groups indicated that poly(4-iso-propenyl-a-methyl) styrene was formed. [Pg.209]

These isomers resulted from the non-stereoselectivity of the initial coupling process typical of the aza-ACE reactions of the 7-isopropylidene-bridged dipolarophile 38, while molecular weight measurements and the presence of an isopropenyl group in the H NMR of each product supported C,A-methano-bridge formation. Such products were considered to arise via the bond reorganisation depicted by the arrows in adduct 156 in which one of the isopropylidene rc-bonds acted as the nucleophile to attack the methylene carbon of the adjacent A-methoxymethyl group. [Pg.46]

Very recently, the formation of azabutadienylosmium complexes through transfer of the isopropenyl group of a phosphine ligand to benzonitriles on a Cp-Os metal complex has been reported (Scheme 79).373... [Pg.445]

The alternative method for making activated esters is base-catalyzed transesterification. Fmoc-amino acids are esterified in excellent yields by reaction with pentafluorophenyl trifluoroacetate at 40°C in the presence of pyridine (Figure 7.13). A mixed anhydride is formed initially, and the anhydride is then attacked by the pentafluorophenoxy anion that is generated by the pyridine. Succinimido, chlorophe-nyl, and nitrophenyl esters were made by this method when it was introduced decades ago. A unique variant of this approach is the use of mixed carbonates that contain an isopropenyl group [Cf C CfyO-COjR]. These react with hydroxy compounds in the presence of triethylamine or 4-dimethylaminopyridine (see Section 4.19) to give the esters and acetone.30 35... [Pg.209]

Contrary to our explanation, it was assumed that a very fast rotation of the isopropenyl groups of 75 and 77 is responsible for the nonoccurrence of 79 and 80, respectively.187 Since 16 and 19 give rise to about 40 a, of alcohols 24,25, and 28,29, respectively, this explanation does not seem to be valid. [Pg.52]

Franssen et al. [24] pointed out an alternative method of production of nootkatone from valencene catalysed by (-i-)-germacrene A hydroxylase, an enzyme of the cytochrome P450 monooxygenase type that was isolated from chicory roots. In general, this enzyme appeared to accept a broad range of sesquiterpenes and hydroxylates exclusively at the side-chain s isopropenyl group. Valencene is an exception it was not hydroxylated at the side chain, but -nootkatol was formed in the first step (Scheme 22.5) it is not yet clear if the second step is enzyme-catalysed. [Pg.499]

By controlled thermal degradation of PIB, end-reactive oligomers can be prepared (53). For example, the resulting end-reactive polymers having one or two tertiary chloro groups can be converted to terminal-unsaturated polymers bearing an isopropenyl group by dehydrochlorination... [Pg.164]

Catalytic activities were shown to strongly depend on the Ni concentration and the molar ratio of borohydride to nickel170 180 182,183. Ni-B powders showed maximum activity when the NaBPLpNiCla ratio was 1.5 (the rate of the hydrogenation of cyclo-heptene was 4.3 x 10 3 mol g-atom Ni-1 s 1 303 K, 1 atm H2)184. When the synthesis, in contrast, was performed in the presence of PVP serving as a protective polymer, a threefold excess of NaBILj was required to achieve maximum activity (191 x 10 3 mol g-atom Ni-1 s-1)184. The polymer-protected sample proved to be especially effective in the hydrogenation of compounds with isopropenyl group (2-methyl-1-hexene and a-methylstyrene). [Pg.860]

Isopropenyl groups are relatively unreactive towards metathesis. 2,5-dimethylhexa-l,5-diene, with an isopropenyl group at both ends, does not react at all in the presence of either 8 or 8W. However, while 2-methylhexa-1,5-diene reacts only at the vinyl end in the... [Pg.1531]

Piers and co-workers (44) have reported that the cuprous chloride catalyzed 1,4-addition of isopropenylmagnesium bromide to the bicyclic enones 127 (R=H or CH3) gave exclusively the bicyclic ketones 128 (R=H or CH3) with the isopropenyl group axially oriented. Interestingly, with their trans ft/B ring junction, these enones are essentially conformationally rigid and their reactivity is in accord with the predictions made on the basis of stereo-electronic effects. [Pg.123]

Isoprenylation of Isopropenyl groups.1 Cyclic terpenes substituted by an isopropenyl group can be converted into sesquiterpenes with the bisabolane skeleton by addition of HOC1 under biphasic conditions to give an allylic chloride (10, 208-209) followed by a zinc-induced reaction with isovaleraldehyde to form an isomeric mixture of homoallylic alcohols. [Pg.135]

The formation of these products may be rationalized in terms of a mechanism involving protonation by sulfuric acid at the terminal carbon of an isopropenyl group to produce an a-carbonium ion intermediate, followed by rearrangement of vicinal silyl group from silicon to this electron-deficient carbon. [Pg.78]


See other pages where Isopropenyl group is mentioned: [Pg.370]    [Pg.210]    [Pg.86]    [Pg.172]    [Pg.983]    [Pg.450]    [Pg.453]    [Pg.459]    [Pg.459]    [Pg.25]    [Pg.760]    [Pg.95]    [Pg.66]    [Pg.104]    [Pg.78]    [Pg.78]    [Pg.1221]    [Pg.59]    [Pg.115]    [Pg.936]    [Pg.44]    [Pg.192]    [Pg.104]    [Pg.359]    [Pg.435]    [Pg.605]    [Pg.204]    [Pg.401]    [Pg.93]    [Pg.86]    [Pg.246]    [Pg.437]    [Pg.440]    [Pg.139]    [Pg.209]   
See also in sourсe #XX -- [ Pg.190 ]

See also in sourсe #XX -- [ Pg.190 ]

See also in sourсe #XX -- [ Pg.190 ]

See also in sourсe #XX -- [ Pg.189 ]

See also in sourсe #XX -- [ Pg.169 , Pg.170 ]

See also in sourсe #XX -- [ Pg.186 ]

See also in sourсe #XX -- [ Pg.177 ]




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Isopropenyl

Isopropenyl acetate groups

Isopropenyl aryl groups

Isopropenylation

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