Of 2-allylphenol

The results were compared with the bromination with bromine. It was apparent that bromine gave /jora-bromides exclusively except 2-allylphenol. As the reaction of 2-allylphenol with bromine gave the mixture of many products (bromine adduct as main product, some ring bromides as by-products, etc.), 2-allylphenol was treated with benzyltrimethylammonium tribromide (BTMA Br3) which was already developed as mild and easy bromine (ref. 10). 

Consequently the bromine adduct was obtained in high yield (83 %). Using NBS and a catalytic amount of the amine, the ratio of the ort/io-brominated phenols was remarkably raised. 2-Allylphenol and o-cresol were considerably orr/io-brominated by NBS even without the amine. In NBS-amine system dibromides as by-products were obtained slightly and any p jra-bromide and bromine adduct in the case of 2-allylphenol were not detected. 

Faster ort/zo-bromination than bromine addition is the reason why bromine adduct was not obtained in the bromination of 2-allylphenol with NBS (ref. 15). 

The use of heterogeneous catalysts in this reaction has also been achieved palladium-montmorillonite clays [93] or palladium/activated carbon [94] in the presence of dppb transformed 2-allylphenols into lactones, the regiose-lectivity of the reaction being largely dependant on the nature of the support. Very recently, palladium complexes immobilized onto silica-supported (polyaminoamido)dendrimers were used as catalysts in the presence of dppb for the cyclocarbonylation of 2-allylphenols, 2-allylanilines, 2-vinylphenols, and 2-vinylanilines affording five-, six-, or seven-membered lactones and lactams. Good conversions are realized and the catalyst can be recycled 3-5 times [95]. 

In addition to the development of new catalysts and reaction conditions for aerobic oxidative heterocycUzation, considerable effort has been directed toward asymmetric transformations. Hosokawa and Murahashi reported the first example of asymmetric Pd-catalyzed oxidative heterocycUzation reactions of this type [157,158]. They employed catalytic [(+)-(Ti -pinene)Pd (OAc)]2 together with cocatalytic Cu(OAc)2 for the cycUzation of 2-allylphenol substrates however, the selectivity was relatively poor (< 26% ee). 

A mixture consisting of 2-allylphenol (35 g), 1,10-dibromodecane (39 g), and potassium carbonate (36 g) dissolved in 150 ml of methyl ethyl ketone was heated to 80°C for 24 hours and then treated with 200 ml of water and 200 ml of hexane. The resulting mixture separated into an organic phase and an aqueous phase. The organic phase was washed with water, dried over Na2S04, and then concentrated. After distillation at 210-215°C 0.1 mmHg, 26 g of product was isolated as a liquid. 

The palladium(n)-catalyzed reaction of 2-allylphenols 27 with carbon monoxide and hydrogen (Equation 7) leads to mixtures of five-, six-, and seven-membered lactones, the content of the latter 28 in the mixture being up to 90-100% <1996JA4264>. 

Contrary to the usual situation, this procedure was found more satisfactory than the rearrangement of allyl phenyl ether by refluxing in diethylaniline. When the ether was refluxed for six hours in three times its volume of diethylaniline, a 61% yield of 2-allylphenol was obtained. 

Isomerization of 2-Allylphenol to 2-Propenylphenol. 2-Allylphenol is dissolved in three times its volume of a saturated solution of potassium hydroxide in methanol part of the solvent is distilled off until the temperature of the liquid rises to 110°, and the residue is refluxed six hours at this temperature. The reaction product is washed free of the base, dried, and distilled, giving a 75% yield of 2-propenylphenol boiling over a range 110-115°/15-16 mm. The compound solidifies in the receiver, and on recrystallization from ligroin forms shining needles melting at 36.5-37° (corr.) in fused state nf> 1.5823, b.p. 230-231° at atmospheric... 

Enantioselective organocatalytic conjugate addition of benzo[A] furan-2-boronic acid to ap-unsaturated aldehydes was utilized to synthesize 2-substituted benzo[Z>]furan with a chiral side chain as illustrated below <07JA15438>. Asymmetric syntheses of 2,2-disubstituted dihydrobcnzo b furans were also achieved by a palladium(II)-catalyzed cyclization of 2-allylphenols in the presence of chiral bisoxazolines <07TL4083 07TL4179>. 

The Prins reaction of 2-allylphenols with glyoxylate esters affords chromans in high yield and with excellent ee though poor diastereoselectivity when a Pt-BINAP catalyst is used which does not assist the competing carbonyl-ene reaction (Scheme 11) <06OL665>. 

Substituted bemofimmes. Treatment of the sodium salt of 2-allylphenol (I) with I eq. of the organometallic reagent in refluxing benzene (3 hr.) gives 2-methyI-... 

T. Hosokawa. K. Maeda, K. Koga. and I. Moritani, Tetrahedron Letters 739 (1973). Prepared by treatment of 2-allylphenol with sodium methoxide. 

Bis[2,3-dihydrobenzofuraii-2-ylmethyl] TeUurium DichIoride 2.4 g (15 mmol) of tellurium dioxide, 4.0 g (30 mmol) of 2-allylphenol, and 3.0 g (70.8 mmol) of lithium chloride in 50 ml of acetic acid are heated under reflux for 1.5 h. The solution is filtered hot, the filtrate is allowed to cool, and the deposited crystals are collected. The solid is dissolved in a hot mixture of ethanol/dichloromethane (1/1, v/v), the solution is evaporated to half of its original volume on a water bath, and then cooled to precipitate the product as a white crystalline solid yield 5.4 g (78%) m.p. 180-184°. 

Isomerization of 2-Allylphenol to 2-Propenylphenol C-Alkylation. Preparation of 2-Cinnamylphenol. ... 

Treatment of 2-allylphenols with mercuric salts gives mercurimethyl-... 

Preparation of 2-Allylphenol. The allyl ether is boiled in a flask under a reflux tube, the course of the rearrangement being conveniently followed by noting the refractive index at frequent intervals. When nu has risen to 1.55 (five to six hours) the rearrangement is substantially complete with the minimum formation of undesirable by-products. To separate a small amount of 2-methyldihydrobenzofuran, the product is dissolved in tivice its volume of 20% sodium hydroxide solution and extracted twice with petroleum ether (30-60°), from which the dihydro-benzofuran residue may be obtained by distillation. Ether should not be used for this extraction as it removes some of the phenol from the alkaline solution. The alkaline solution is acidified and the phenpl extracted with ether the extract is dried over calcium chloride and distilled under diminished pressure. A 73% yield of material boiling at 103-105.5°/19 mm., no 1.5445, is obtained. 2-Allylphenol is a colorless liquid, of guaiacol-like odor, with the following properties b.p. 220°/ 760 mm., 99°/12 mm., nf) 1.5453. ... 

Bromination. Electron-rich aromatic compounds undergo nuclear bromination readily with the dibromohydantoin. To improve its reactivity toward less reactive arenes (e.g., t>-anisaldehyde) the addition of trimethylsilyl triflate has positive effects. Noteworthy are the different reaction profiles of 2-allylphenol in the presence of M SiOTf 2-bromomethyldihydrobenzofuran is the product in the presence of MejSiOTf. 

Remarkable improvements have been achieved in the optimization of the rate and yield of these thermal reactions (typically 150-220 °C), such as the use of microwave irradiation or catalysts. For instance, allyl phenyl ether at 220 °C gives an 85% yield of 2-allylphenol in 6 h, but the reaction time drops to 6 min by using microwave ovens and the yields also increase up to 92% . On the other hand, Lewis acids, such as BCR , BF3-Et20, Et2AlCl, TiCLt and (i-PrO)2TiCl2 have been successfully used to catalyse this rearrangement reaction under mild conditions. Other catalysts such as Ag and complexes or zeolites have also been employed. 

The isomerization of 2-allylphenol 121 to 2-propenylphenol 122 catalyzed by the ortho-metallated complex Rh[P(OPh)3]3[P(OPh)2(OCeH4)] produces only one isomer (equation 54) °". ... 

A Pd-catalyzed tandem reaction was developed to synthesize a group of interesting benzo[fc] furans as depicted below <05CC271>. The Pd-catdyzed cyclization of propargylic carbonates was also applied to make 2,3-dihydrofurans and benzofurans <05T4381>. Furthermore, an oxidative cyclization procedure catalyzed by Pd(II) and pyridine in the presence of molecular oxygen was carried out on a variety of 2-allylphenols to form 2-substituted as well as 2,2-disubstituted benzo[fc]furans <05JA17778>. 

Ruthenium In one of the earliest examples of a transition metal-catalyzed hydroalkoxylation reaction from 1998, the cyclization of 2-allylphenols to benzo-dihydrofurans was catalyzed by a cocktail of ruthenium chloride, silver- and copper triflates, and a phosphane ligand (Scheme 8a) [44]. A control experiment implied that triflic acid alone was ineffective as catalyst, but this experiment is at variance with a later report where 2-allylphenol was cyclized using only 5 mol% of triflic acid as catalyst (CH2CI2, 40°C, 3 h) [45]. 

For organic encapsulation we have used the electrochemical synthesis of poly(oxy-phenylene) as originally presented by Mengoli et al. It is done by the electrochemical oxidation of 2-allylphenol in water/methanol/butylcellosolve mixture to yield poly(oxyphenyl-ene). This electrooxidation is done in the presence of allylamine in order to minimize the competing passivation of the substrate and to crosslink the linear polymer during the curing step. 

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