Alkoxy phenol

Weak Medium 300 15b Alcohols, phenols, and intermolecular hydroxyl to carbonyl bonding <100 10 100-300 50 1.2- Diols, a- and most /3-hydroxy ketones o-chloro and o-alkoxy phenols 1.3- Diols some /3-hydroxy ketones /3-hydroxy amino compounds nitro compounds... 

Alkyl-substituted phenols have been studied extensively by the same authors, and Rf values have been summarized in Table 8 in similar solvent systems for alumina and cellulose, respectively. At the end of Table 8 the properties of some alkoxy phenols are given. 

A synthetic pathway to the 4-alkoxyphe-nyl 4-alkoxybenzoates is shown in Fig. 32. The pathway involves two alkylations one of 4-hydroxybenzoic acid using an alkyl halide in the presence of sodium hydroxide and ethanol, and the other of 1,4-dihydroxyben-zene using an alkyl halide in the presence of sodium hydroxide and dioxane. Activation of the acid with thionyl chloride to give the acid chloride and reaction with the alkoxy-phenol in the presence of a base such as tri-ethylamine yields the final esters. 

Synthesis. Titanium alkoxy halides are intermediates in the preparation of alkoxides from a titanium tetrahaUde (except the fluoride) and an alcohol or phenol. If TiCl is heated with excess primary alcohol, only two chlorine atoms can be replaced and the product is dialkoxydichlorotitanium alcoholate, (RO)2TiCl2 ROH. The yields are poor, and some alcohols, such as aHyl, ben2yl, and /-butyl alcohols, are converted to chlorides (46). Using excess TiCl at 0°C, the trichloride ROTiCl is obtained nearly quantitatively, even from sec- and / f/-alcohols (47,48). 

O- Alkylation is comparable to A/-alkylation, but since the sodium salts are water-soluble it is most convenient to treat the phenol or naphthol in aqueous caustic solution with dimethyl sulfate or diethyl sulfate. These are comparatively expensive reagents, and therefore, alkoxy groups are introduced at a prior stage by a nucleophilic displacement reaction whenever possible. 

Alkoxyl tion. The nucleophilic replacement of an aromatic halogen atom by an alkoxy group is an important process, especially for production of methoxy-containing iatermediates. Alkoxylation is preferred to alkylation of the phenol wherever possible, and typically iavolves the iateraction of a chloro compound, activated by a nitro group, with the appropriate alcohol ia the presence of alkaU. Careful control of alkaU concentration and temperature are essential, and formation of by-product azoxy compounds is avoided by passiag air through the reaction mixture (21). 

Aromatic rings are hydrogenated with a variety of catalysts. However, aromatic alkoxy and hydroxyl substituents are susceptible to hydrogenolysis under most conditions used to saturate the ring. Hydrogenolysis does not occur to any appreciable extent with ruthenium catalysts even though high temperatures and pressures are required. Thus, substituted phenols are... 

Cross-conjugated dienones are quite inert to nucleophilic reactions at C-3, and the susceptibility of these systems to dienone-phenol rearrangement precludes the use of strong acid conditions. In spite of previous statements, A " -3-ketones do not form ketals, thioketals or enamines, and therefore no convenient protecting groups are available for this chromophore. Enol ethers are not formed by the orthoformate procedure, but preparation of A -trienol ethers from A -3-ketones has been claimed. Another route to A -trien-3-ol ethers involves conjugate addition of alcohol, enol etherification and then alcohol removal from la-alkoxy compounds. 

Reaction of 9,10-difluoro-3-methyl-2,3-dihydro-7-oxo-7//-pyrido[l,2,3- /e]-l,4-benzoxazine-6-carboxylic acid (252 X = F, R = H, R = Me) with 8 M aquous solution of KOH under reflux for 6 h, and in the presence of an alcohol or phenol afforded 10-hydroxy, 10-alkoxy and 10-aryloxy derivatives, respectively (96JAP(K)96/291144, 99MI5). 

As discussed in Section 8.10, dediazoniation in methanol or ethanol yields mixtures of the corresponding aryl ethers and arenes, except with alcohols of very low nucleo-philicity such as trifluoroethanol, in which the aryl ether is the main product. Therefore aryl ethers are, in general, synthesized by alkylation of the respective phenol. Olah and Wu (1991) demonstrated, however, that phenylalkyl and aryl ethers can be obtained in 46-88% yield from benzenediazonium tetrafluoroborate using alkoxy- and phenoxytrimethylsilanes in solution in Freon 113 (l,l,2-trichloro-l,2,2-tri-fluoroethane) at 55-60 °C with ultrasonic irradiation. As seen from the stoichiometric... 

A greatly enhanced chemoselective formation of phenol is observed for alkoxy(alkenyl)carbene complexes compared to alkoxy(aryl)carbene complexes. This behaviour reflects the ease of formation of the rf-vinylketene complex intermediate E starting from alkenylcarbene complexes for aryl complexes this transformation would require dearomatisation. 

Merlic et al. were the first to predict that exposing a dienylcarbene complex 126 to photolysis would lead to an ort/zo-substituted phenolic product 129 [74a]. This photochemical benzannulation reaction, which provides products complementary to the classical para-substituted phenol as benzannulation product, can be applied to (alkoxy- and aminocarbene)pentacarbonyl complexes [74]. A mechanism proposed for this photochemical reaction is shown in Scheme 54. Photo activation promotes CO insertion resulting in the chromium ketene in-... 

Hydroxy- bzw. 2-Alkoxy-alkyl)-phenyl-sulfone konnen in DMF in Gegenwart von Essigsaure Oder Phenol als Protonendonator an Quecksilber kathodisch an der S-CAlkyl-Bindung unter Bildung von Olefinen (bis 90% d. Th.) gespalten werden. Mit zunehmender Protonendonator-Konzentration nimmt der Anteil des Alkans zu (bis zu 40% d.Th.) ... 

The 1,3,4-oxadiazole 113 is formed from the azo compound 112 by the action of triphenylphosphine <96SL652>. A general synthesis of 1,3.4-oxadiazolines consists in boiling an acylhydrazone with an acid anhydride (e.g., Scheme 18) <95JHC1647>. 2-Alkoxy-2-amino-l,3,4-oxadiazolines are sources of alkoxy(amino)carbenes the spiro compound 114, for instance, decomposes in boiling benzene to nitrogen, acetone and the carbene 115, which was trapped as the phenyl ether 116 in the presence of phenol <96JA4214>. 

A blend of a polyoxyalkylene-polysiloxane copolymer and an alkoxy-lated phenol-aldehyde resin is useful as a demulsifier [1457, 1458]. 

In general, modification or deletion of the Cl phenolic hydroxyl group results in significantly reduced CBi receptor affinity [93]. A number of 1-deoxy and 1-alkoxy A -THC analogues have been shown to be selective ligands for the CB2 receptor (see below). 

The isolated double bonds in the dihydro product are much less easily reduced than the conjugated ring, so the reduction stops at the dihydro stage. Alkyl and alkoxy aromatics, phenols, and benzoate anions are the most useful reactants for Birch reduction. In aromatic ketones and nitro compounds, the substituents are reduced in preference to the Dissoiving-Memi... 

Hexaco-ordinated Phosphorus Compounds. - The reaction of PCt with alkylammonium fluorides in the presence of secondary amines gives PF5-amine adducts (132)60. The additional presence of alcohols or phenols leads to the formation of alkoxy- or aroxypenta-f luorophosphates, ROPF -. The PF -amine adducts may also be converted into ROPF - by treatment with alcohols or into ArNHPF -by treatment with primary arylamines. 

---