Phenols, tetra-substituted

Intermolecular hydroalkoxylation of 1,1- and 1,3-di-substituted, tri-substituted and tetra-substituted allenes with a range of primary and secondary alcohols, methanol, phenol and propionic acid was catalysed by the system [AuCl(IPr)]/ AgOTf (1 1, 5 mol% each component) at room temperature in toluene, giving excellent conversions to the allylic ethers. Hydroalkoxylation of monosubstituted or trisubstituted allenes led to the selective addition of the alcohol to the less hindered allene terminus and the formation of allylic ethers. A plausible mechanism involves the reaction of the in situ formed cationic (IPr)Au" with the substituted allene to form the tt-allenyl complex 105, which after nucleophilic attack of the alcohol gives the o-alkenyl complex 106, which, in turn, is converted to the product by protonolysis and concomitant regeneration of the cationic active species (IPr)-Au" (Scheme 2.18) [86]. 

TCDD (perz-dechlorination), from one, which does not produce this tetra-CDD isomer (perz-lateral dechlorination). The relative contribution of each pathway (i.e., the ratio of 2,3,7,8- to other tetra-substituted congeners) observed is dependent on the system tested, whereby the presence of phenolic compounds appears to shift the pathway toward peri-dechlorination and enhances the total yield of lesser chlorinated products [433]. 

Acourtia isocedrene (169) is one of the highly oxygenated isocedrenes first isolated from Acourtia Nana. Retrosynthetic pathways are shown in Scheme 33, where the resulting cycloaddition product (170) from penta-substituted phenol 171 has the same carbon skeleton as that of 169, while addition of one carbon unit to 172 is needed in the case of a tetra-substituted phenol 173. 

On constant current electrolysis (9.4 mA 2 Fmol ), 171 underwent intramolecular cationic [5 + 2] cycloaddition to afford the /3-isomer 170 as a sole product (34%). In the case of the tetra-substituted phenol 173, it was converted to a mixture of two stereoisomers (172a and 172b) in 70% yield (relative ratio a//S = 3/1), as shown in Scheme 34 . Both of them were converted successfully to the target molecule 169 . 

SCHEME 34. Anodic oxidation of penta- and tetra-substituted phenols... 

Sulfur-containing hindered phenolics include diphenols with alkylthio bridges, e.g., l,6-bis(3,5-di-t-butyl-4-hydroxyphenylthio) hexane [50] tri- and tetra-(substituted hydroxyphenylthio) alkanes and cycloalkanes, e.g., l,l,2,2-tetrakis(3,5-di-t-butyl-4-hydroxyphenylthio)ethane and 1,1,3-tris (3- butyl-5-t-octyl-4-hydroxyphenylthio)-3,5,5-trimethylcyclohexane [51, 53] and di-(substituted hydroxyphenylthio)alkanes and cycloalkanes [52]. 

Figure 18.5 exhibits the curve of solid-state Si NMR spectra of phenolic nanocomposite. Condensed siloxane species for TEOS in which a silicon atom through mono-, di, tri, tetra-substituted siloxane bonds were designated as Q, respectively. The definition of Q is shown in Fig. 18.6. The chemical shifts —91, —101, —109 ppm of Q, Q, Q, respectively, were in good agreement with the literature. ...

Determination of organic compounds. The application of photometric titrimetry to organic compounds may be exemplified by the titration of phenols. This can be carried out by working at the /max value (in the ultraviolet) for the phenol being determined (see Section 17.50). It has been shown that by titrating with tetra-n-butylammonium hydroxide and using propan-2-ol as solvent, it is possible to differentiate between substituted phenols.24... 

Tetra(o-aminophenyl)porphyrin, H-Co-Nl TPP, can for the purpose of electrochemical polymerization be simplistically viewed as four aniline molecules with a common porphyrin substituent, and one expects that their oxidation should form a "poly(aniline)" matrix with embedded porphyrin sites. The pattern of cyclic voltammetric oxidative ECP (1) of this functionalized metal complex is shown in Fig. 2A. The growing current-potential envelope represents accumulation of a polymer film that is electroactive and conducts electrons at the potentials needed to continuously oxidize fresh monomer that diffuses in from the bulk solution. If the film were not fully electroactive at this potential, since the film is a dense membrane barrier that prevents monomer from reaching the electrode, film growth would soon cease and the electrode would become passified. This was the case for the phenolically substituted porphyrin in Fig. 1. 

In all of, these cases substitution of the second alkyl can then occur to yield the dialkoxide or diphenoxide. This allowed the isolation of the monomeric beryllium phenoxide Be(OAr )2 (OAr = 2,6-di-t-butylphenoxide).98 The alkyls of the Group IV metals, MR (M = Ti, Zr, Hf), undergo rapid reactions with common alcohols and phenols yielding eventually the corresponding tetra-alkoxides or -phenoxides and four equivalents of alkane.97,100 With very bulky substituted alcohols or phenols the reactivity can be very sluggish, in some cases leading to only partial substitution (equation 28). 66,100... 

Chloranil.—We have spoken of the fact that halogan derivatives of quinones are formed as addition products, the di- and tetra-products being known. The halogens form other derivatives also in which the halogen is substituted for hydrogen of the benzene ring. These are true substituted quinones. The tetra-chlor quinone, C6CI4O2, is known as chlor-anil and is formed when aniline or phenol is treated with potassium chlorate and hydrochloric acid. 

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