Derivatives of Resorcinols

The facile decarboxylation of resorcinol carboxylic acids and notably of orsellinic acids in alkaline solution poses a problem during their syntheses in high yield. For this reason the synthesis of alkoxycarbonyl derivatives is usually adopted followed by acidic hydrolysis. The removal of the protective acetyl groups in the compound shown was effected preferentially without hydrolysis of the ester group. Methyl 2,6-diacetoxybenzoate in toluene saturated with water when add to a catalyst (prepared from 4-toluenesulphonic acid monohydrate and silica gel) and stirr at 86°C during 6 hours, afford methyl 

2-Acylresorcinols have been derived by the aromatisation of 2-acyl-3-hydroxy-cyclohex-2-en-1-ones (R = alkyl) through oxidation with mercuric acetate (ref.22). 

There has been considerable activity in the synthesis of orsellinic acids in the past decade. On account of their ready decarboxylation all these procedures also give access to 5-alkylresorcinols. These routes are summarised in the scheme shown. Homologous alkyl acetoacetates (R = R = alkyl) with thallium ethoxide or sodium hydride followed by reaction with diketene (route a) afford the corresponding homologous alkyl orsellinates (ref.23). In a related method (route b) methyl orsellinate (R = Me) results from the interaction of the monoanion with the dianion of methyl acetoacetate (ref.24). 

A closely related methodology (route c) involves the dianion from a diketone (R = Me) with the anion of dimethyl malonate (R = Me) (ref.25). The bis-trimethylsilyl ether from methyl acetoacetate has been interacted with the ketalised acid chloride shown (R = CgH ) to furnish the methoxy carbonyl derivative of olivetol (route d) (ref.26). It was also found that pentane-2,4-dione with dimethyl malonate in the presence of sodium hydride afforded methyl orsellinate (ref.26). In a biomimetic approach (route e) a tetraketone has been enzymically cyclised to give the corresponding orsellinic acid (R=H, R = alkyl) (ref. 27). 

To contrast with the preceding strategies, 2-methoxycarbonylresorcinol compounds can be synthesised from the bis-trimethylsilyl derivative of methyl acetoacetate and the dimethyl acetal of methyl 3-oxooctanoate (ref.28). 

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Fluororesorcinol can be prepared from derivatives of resorcinol and fluo-roxytrifluoromethane [15, 24] (equation 4) or by fluorination of resorcinol with cesium fluoroxysulfate [25] (equation 5). Reaction of acetyl hypofluorite with M-acetyl-O-methyltyrosine methyl ester provides a good route to 3-fluorotyrosine derivatives [26] (equation 6). 

Particularly in the older literature, the structure of the nitrosophenols was not clearly established. Thus, for example, the dinitroso derivative of resorcinol is presumed to be the tautomeric dioxime [32] shown in Eq. (20). 

We have determined that the assembly process is tolerant to substituents placed along the periphery of the template [7], In particular, derivatives of resorcinol with substituents unable to disrupt the hydrogen bonds between the templates and reactants (e.g. -R, -OR) have been found to serve as templates. Thus, cocrystallization of 5-methoxyresorcinol (5-OMe-res) with 4,4 -bpe produced the four-component complex, 2(5-OMe-res)-2(4,4/-bpe), with two olefins aligned parallel and separated by 3.66 A. UV-irradiation of the solid with broadband UV-radiation produced 4,4 -tpcb in quantitative yield. 

Chromogens of different classes, viz., arylazo derivatives of resorcinol, naphthols, naphthylamines, chromotropic acid and its cyclic modification, and also some formazans, were investigated by Fedorov et al.95 using 13C CP/MAS NMR. Usually only negligible changes of 6(13C) were found on comparing solution and solid-state spectra. Table 14 shows solution and the solid-state data for azo resorcinols in alkaline media existing in paro-quinoidic structure 33, not in the ortho one typical of some other compounds. 

Among polyhydric phenols, only the nitro derivatives of resorcinol have gained considerable practical importance. The nitro derivatives of phloroglucinol may also be of some value. Both phenols have hydroxyl groups in the meta position to each other, thus enabling the introduction of three nitro groups. Among dinitro derivatives, those of pyrocatechol have found some uses. 

Among all the possible nitro derivatives of resorcinol only di- and tri-nitroresorci-nols are of practical value. Both are used as initiating explosives in the form of lead salts (Vol. III). The lead salt (Pb2+) of dinitroresorcinol is also of some practical value and in this connection some data characteristic of the compound will be given. 

Discovery of the dienone-phenol rearrangement of quinol acetates has made possible the synthesis of dihydric phenols that were difficult of access by other routes. The starting materials are obtained from phenols and lead tetraacetate, and with acetic anhydride and sulfuric acid (Thiele acetylation) or with boron trifluoride in ether they give, respectively, di- and mono-acetyl derivatives of resorcinol or hydroquinone.309 When treated with lN-sodium hydroxide, 0-quinol acetates of type (1) undergo nucleophilic addition of an OH" ion, giving resorcinol derivatives (2).310 Occurrence of the reaction is considered... 

Organolithium compounds, generally phenyl- or butyllithium, can be used, in the same way as(triphenylmethyl)sodium (see page 917), as base for C-alkyla-tion, since in certain cases they react by metal exchange with activated hydrocarbons. For instance, the 2-lithio derivative of resorcinol dimethyl ether is formed in 70% yield on reaction with phenyllithium. The organolithium compounds thus obtained react readily with alkyl halides or sulfates, forming a carbon-carbon bond 326 for example, 2,6-dimethoxytoluene is formed by... 

One of the most interesting studies of the effect of various alkyl groups on physiological activity is illustrated by the alkyl derivatives of resorcinol, which are discussed under Hexylresorcinol. The bactericidal action at first increases with the length of the side chain and then diminishes because of decreased solubility of the alkylresorcinol. Coincident with this increase is found a decrease in toxicity. 

In the case of the dihydroxybenzenes, the alkyl derivatives of resorcinol have been carefully investigated, and it is found that the entrance of the methyl group into the ring, forming orcinol, depresses the bactericidal power. The influence of higher alkyl groups on the nucleus of the resorcinol molecule is considered under Hm lresorcinol (q.v.). 

Kobayashi, K., Asakawa, Kato, Y, Aoyama, Y. (1992). Complexation of hydrophobic sugars and nucleosides in water with tetrasulfonate derivatives of resorcinol cyclic tetramer having a polyhydroxy aromatic cavity Importance of guest-host CH-tc interaction, J. Am. Chem. Soc., 114 10307. 

As mentioned above, quinones can be formed from derivatives of resorcinol or catechol as well as from the parent hydroxyl compounds. When dimethoxy compound 144 was treated with ceric ammonium nitrate (CAN), for example, a 92% yield of quinone 145 was obtained as part of De Kimpe s synthesis of isagarin.222... 

Incoiporation of metal precursors into carbon aerogel is traced back to incorporation of metal salts into RF solution before the sol-gel process. Simple physical adsorption of metal salts on wet gel matrices caused leaching of the metal ions during washings required by the sol-gel process. This resorted researchers to use derivatives of resorcinol (e.g.,... 

Resorcinol reacts with formaldehyde under alkaline conditions to form mixtures of addition and condensation products. The major reactions include (1) the formation of hydroxymethyl (-CH2OH) derivatives of resorcinol, (2) the condensation of the hydroxymethyl derivatives to form methylene (-CH2-) and methylene ether (-CH2OCH2-) bridged compounds, and (3) the disproportionation of methylene ether bridges to form methylene bridges plus formaldehyde as a by-product [29]. These reactions have been studied extensively by NMR [58]. The crosslinked polymer grows into discrete particles, which eventually form a three-dimensional network or a gel (Chap. 13). 

The term alkyhesorcinols is used collectively for the group of 5-alkyl, 5-alkenyl, 5-alkadienyl and minor 5-(2-oxoalkyl) and 5-(2-oxoalkenyl) derivatives of resorcinol (benzene-l,3-diol, 10-1). The resorcinol substituents have straight chains with an odd number of carbon atoms. The most common substituents have 13 to 29 carbon atoms. 

Preparation by reaction of 2-chloro-3-hydroxyben-zoyl chloride with bis(trimethylsilyl) derivative of resorcinol in the presence of stannic chloride (or titanium tetrachloride or aluminium chloride) in refluxing methylene chloride for 2 h [921]. 

Cannon JR, Cresp TM, Metcalf BW, Sargent MV, Vinliguerra G, Elix JA (1971) The Bromination of some Derivatives of Resorcinol. J Chem Soc (C) 3495... 

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