Unsaturated phenols formation

Fluorinated unsaturated alcohols have been prepared from the point of view of potential fluo-rinated monomers with a reactive pendant group. There seem to be no examples of the preparation of fluorinated unsaturated phenols by dehalogenation. Examples of the formation of fluorinated unsaturated alcohols are listed in Table 7. 

An unusual reaction was been observed in the reaction of old yellow enzyme with a,(3-unsat-urated ketones. A dismutation took place under aerobic or anaerobic conditions, with the formation from cyclohex-l-keto-2-ene of the corresponding phenol and cyclohexanone, and an analogous reaction from representative cyclodec-3-keto-4-enes—putatively by hydride-ion transfer (Vaz et al. 1995). Reduction of the double bond in a,p-unsaturated ketones has been observed, and the enone reductases from Saccharomyces cerevisiae have been purified and characterized. They are able to carry out reduction of the C=C bonds in aliphatic aldehydes and ketones, and ring double bonds in cyclohexenones (Wanner and Tressel 1998). Reductions of steroid l,4-diene-3-ones can be mediated by the related old yellow enzyme and pentaerythritol tetranitrate reductase, for example, androsta-A -3,17-dione to androsta-A -3,17-dione (Vaz etal. 1995) and prednisone to pregna-A -17a, 20-diol-3,ll,20-trione (Barna et al. 2001) respectively. 

Various aldehydes 184 and alcohols have been shown to be competent in the redox esterification of unsaturated aldehydes in the presence of the achiral mesityl triazo-lium pre-catalyst 186. Both aromatic and aliphatic enals participate in yields up to 99% (Table 13). Tri-substituted enals work well (entry 3), as do enals with additional olefins present in the substrate (entries 4 and 7). The nucleophile scope includes primary and secondary alcohols as well as phenols and allylic alcohols. Intramolecular esterification may also occur with the formation of a bicyclic lactone (entry 8). 

Very recently, attempts have been made to develop PP/EOC TP Vs. In order to make TPVs based on PP/EOC blend systems, phenolic resin is ineffective because the latter needs the presence of a double bond to form a crosslinked network structure. Peroxides can crosslink both saturated and unsaturated polymers without any reversion characteristics. The formation of strong C-C bonds provides substantial heat resistance and good compression set properties without any discoloration. However, the activity of peroxide depends on the type of polymer and the presence of other ingredients in the system. It has been well established that PP exhibits a (3-chain scission reaction (degradation) with the addition of peroxide. Hence, the use of peroxide only is limited to the preparation of PP-based TPVs. Lai et al. [45] and Li et al. [46] studied the fracture and failure mechanism of a PP-metallocene based EOC based TPV prepared by a peroxide crosslinking system. Rajesh et al. 

The pyridine-catalyzed aromatic proton exchange with deuterium provides a simple indication of the ability of a phenol to participate in chromene formation. Only those phenols which undergo exchange react with the unsaturated carbonyl compound, the attack occurring at the positions of deuteration (64JA2084). 

The intramolecular alkoxy- or phenoxy-mercuration of unsaturated alcohols or phenols, respectively, provides an exceptionally useful process for the formation of cyclic ethers, particularly those bearing a five- or six-membered ring (equation 263).415... 

Selective alkylation of the y position of a,/3-unsaturated esters, aldehydes, or ketones can be achieved if a sterically demanding Lewis acid is used to coordinate to the carbonyl group and inhibit a-alkylation by steric shielding [123, 125, 126] (Scheme 5.11). This method not only results in high regioselectivity but also enables highly stereoselective aldol-type additions to be performed in good yields, even with sensitive substrates, such as a,/3-unsaturated aldehydes [126]. Thus, when two dia-stereotopic y positions are available, the addition of a bulky aluminum phenolate leads to the clean formation of the Z-alkene (second and third examples, Scheme 5.11). 

Recently, Bode et al. were able to demonstrate that the products formed after generation of the homoenolate equivalents 67 are determined by the catalytic base [64]. Strong bases such as KOt-Bu led to carbon-carbon bond-formation (y-butyrolactones), while weaker bases such as diisopropylethylamine (DIPEA) allowed for protonation of the homoenolate and the subsequent generation of activated carboxylates. The combination of triazolium catalyst 72 and DIPEA in THF as solvent required no additional additives and enabled milder reaction conditions (60 °C), accompanied by still high conversions in the formation of saturated esters out of unsaturated aldehydes (Scheme 9.21). Aliphatic and aromatic enals 62, as well as primary alcohols, secondary alcohols and phenols, are suitable substrates. a-Substituted unsaturated aldehydes did not yield the desired products 73. 

The mechanism of phenol amination on MgO can be formulated in an identical way since it is known that ammonia also dissociates heterolyti-cally on the most unsaturated Mg 0 pairs (264) located at edges, steps, and corners, with formation of surface NH2 and OH species (see Section IV.A.5). Since phenol (an acidic molecule) is adsorbed on all surface Mg2 O2 pairs, the most plausible adsorption interaction mechanism is that shown in Scheme 8. The densely packed negatively charged OH, phenoxide, and amino groups are then expected to readily react at the reaction temperature with elimination of aniline and water. 

In Fig. (12) keto ester (94) was selected as starting material. It was converted to the formyl derivative (95) which yielded a,P-unsaturated aldehyde (96) by treatment with DDQ. Michael addition of the sodium enolate of tert-butyl- isovalerylacetate to aldehyde (96) afforded the adduct (97) as a mixture of C-ll diastereomers. By fractional crystallization one of the adducts could be separated but for the synthetic purpose the mixture was not separated. Treatment of the adduct (97) with p-toluenesulfonic acid in glacial acetic acid caused t-butyl ester cleavage, decarboxylation and cyclodehydration leading the formation of tricyclic enedione (98) in 80% yield. This approach was previously utilized by Meyer in the synthesis of nimbiol [29], Treatment of (98) with pyridinium bromide perbromide, followed by hydrogenolysis with palladium and carbon caused aromatization of (98) leading the formation of the phenolic ester (99). 

The level of polyunsaturates in the hydrophobe of a cationic surfactant influences its liquidity and also its resistance to oxidative degradation and color formation [24, 37]. The higher the polyunsaturate level and consequently the iodine value, the higher the liquidity and the higher the aqueous concentration of a softener dispersion that can be achieved. Products with high or even modest degrees of unsaturation frequently require the addition of an antioxidant such as the hindered phenol derivatives, butylated hydroxy toluene and butylated hydroxy anisole [24, 25, 38]. 

Besides simple enones and enals, less reactive Michael acceptors like /3,/3-disubstituted enones, as well as a,/3-unsaturated esters, thioesters, and nitriles, can also be transformed into the 1,4-addition products by this procedure.44,44a,46,46a The conjugate addition of a-aminoalkylcuprates to allenic or acetylenic Michael acceptors has been utilized extensively in the synthesis of heterocyclic products.46-49 For instance, addition of the cuprate, formed from cyclic carbamate 53 by deprotonation and transmetallation, to alkyl-substituted allenic esters proceeded with high stereoselectivity to afford the adducts 54 with good yield (Scheme 12).46,46a 47 Treatment with phenol and chlorotrimethylsilane effected a smooth Boc deprotection and lactam formation. In contrast, the corresponding reaction with acetylenic esters46,46a or ketones48 invariably produced an E Z-mixture of addition products 56. This poor stereoselectivity could be circumvented by the use of (E)- or (Z)-3-iodo-2-enoates instead of acetylenic esters,49 but turned out to be irrelevant for the subsequent deprotection/cyclization to the pyrroles 57 since this step took place with concomitant E/Z-isomerization. 

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