Derivatives of 1,3-Dihydroxy Compounds

In this quite important group, side-chain and etherification reactions are considered first in benzenoid compounds and then reactions of more complex methylenedioxy compounds. 

To 4-(dimethylamino)pyridinium chromate (5 mole), obtained from 

4-dimethylaminopyridine and chromium trioxide in 1.65M hydrochloric acid, in dichloromethane solution 3,4-methylenedioxybenzyl alcohol was introduced in one portion. After stirring for 15 hours, 3,4-methylenedioxybenzaldehyde was isolated in 98% yield. The reagent is selective for allylic and benzylic alcohols (ref. 94). 

The reaction of allylic Grignard reagents with aldehydes to produce allylic carbinols does not always proceed smoothly. In the reaction of 3,4-methylene dioxybenzaldehyde with allyl alcohol (1.5-3.0 moles) at ambient temperature 

In the hydrogenation of 4-(3-cyano-1-oxopropyl)methylenedioxybenzene in methanol containing freshly-prepared Raney nickel for 8 hours at tOO C, ring closure afforded a 90% yield of 2-(benzo[1,2-d]-[1,3]dioxo-5-yl)pyrroline (ref.96). 

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The use of 1,4-dinucleophiles is more common due to accessibility of 1,2-dihydroxy compounds, 1,2-diamines, and their derivatives. Benzo-9-crown-3 ether is easily available from pyrocatechol and l-chloro-2-(2-chloroethoxy)ethane <1998ANC5259, 2002JOC2065>. Similar procedure for 2,3-dihydroxynaphthalene resulted in a 4.5% yield of naphtha-9-crown-3 <2000JST(526)185>. 

The pentacoordinate silicon compounds 94,23 95,23 96-98,60 99,60,61100,61,62 101-103,60 104,61,62 105,62 106,62 and 10761,63 are monocyclic zwitterionic A5S7-silicates with an Si02FC2 skeleton. The chiral zwitterions each contain one bidentate diolato(2-) ligand that formally derives from 1,2-dihydroxy-benzene, salicylic acid, glycolic acid, oxalic acid, benzohydroximic acid (tautomer of benzohydroxamic acid), 2-methyllactic acid, or (S)-mande-lic acid. 

Several saturated parent systems shown in Scheme 1, especially (2), (4) and (7), have been incorporated into spiro compounds or have been fused with a variety of non-aromatic carbocyclic or heterocyclic rings. Unsaturated compounds with an endocyclic carbon-carbon double bond, formally possible in all systems with three adjacent heteroatoms, are only known in very few cases (e.g. cyclic sulfites and sulfates of enediols) or in the form of benzo or other condensed systems (mainly cyclic sulfites and sulfates of aromatic 1,2-dihydroxy compounds). For details concerning the various types of derivatives, see Section 4.33.4.2. 

The formation of 1,2-diol products from alkenes can be achieved using Prevost s reagent - a solution of iodine in carbon tetrachloride together with an equivalent of silver(l) acetate or silver(I) benzoate. " Under anhydrous conditions, this oxidant yields directly the diacyl derivative of the anh-diol (Prdvost conditions), while in the presence of water the monoester of the syn-diol is obtained (Woodward conditions). Thus, treatment of a cw-alkene with iodine and silver benzoate in boiling carbon tetrachloride under anhydrous conditions gives the tra 5-dibenzoate (5.92). With iodine and silver(I) acetate in moist acetic acid, however, the monoacetate of the cw-1,2-dihydroxy compound is formed. 

The suitability of ethers derived from 1,4-dihydroxy-1,2,3,4-tetrahydro-naphthalene (DHTN) in the design of polymers susceptible to catalyzed thermolytic cleavage is demonstrated by the behavior of its bis-p-nitrophenyl ether derivative upon treatment by a trace of acid. Figure 2, curve A, shows the H-NMR spectrum of the starting compound, while curve B shows the product which is obtained upon addition of triflic acid. It is readily seen from these spectra that quantitative cleavage into naphthalene and p-nitrophenol is obtained as elimination occurs easily to afford the aromatic product. The driving force in this reaction is the facile aroma-tization which produces naphthalene. 

Several of the above approaches have proved appropriate for the preparation of alkylated derivatives whilst related but somewhat modified chemistry is required for other substituted compounds routes depicted in Scheme 24 are examples of methods for the preparation of alkoxy derivatives (47JA2449). Compounds such as 2-hydroxyketones and 2-mercap-toketones dimerize reversibly to give 2,5-dihydroxy derivatives of 1,4-dioxanes and 1,4-dithianes respectively (B-57MI22600, 66HC(21-2)104l). 

More recently benzoic acid derivatives (MW 122-170) have also been shown to be astringent (17). The most astringent compounds, salicylic (2-hydroxy benzoic acid) and gentisic (2,5 dihydroxy benzoic acid) acids, were ortho substituted, but neither had vicinal hydroxyl groups. Both derivatives had lower pHs than the non-ortho substituted ones, which may have contributed not only to sourness but also to astringency. McManus et al (1981) (18) proposed previously that simple phenols which contain 1,2 dihydroxy or 1,2,3 trihydroxy groups (such as epicatechin or catechin) may cross link and thereby precipitate proteins. It could be speculated that ortho substitution conveys some kind of binding capability similar to that of flavan-3-ols or polyphenolics of hi er MW. 

The metabolic oxidation of otefinic carbon-carbon double bonds leads to the corresponding epoxide (or oxiranc). Epoxides derived from olefins generally tend to be somewhat more stable than the arene oxides formed from aromatic-compounds. A few epoxides arc stable enough to be direclly mcasurable in biological fluids (e.g.. plasma, urine). Like their arene oxide counterparts, epoxides- are susceptible to cnz.ymatic hydration by epoxide hydra.se to form lran,s-. 2-dihydrodiols (al.so called 1,2-diols or 1.2-dihydroxy com-... 

Products from the pyrolysis of cellulose in the absence of a catalyst were found to be mainly derivatives of 1,6-anhydro-D-glucoseand other, unsaturated, products. One product, formed in 1.4% yield, was found to be 1,5-anhydro-4-deoxy-D- /yc ro-hex-l-en-3-ulose. This product was also formed during the pyrolysis of amylose, amylopectin, and laminarin. A further product from cellulose, probably formed as an oxidation product, was 3,5-dihydroxy-2-methyl-4/f-pyran-4-one. Sixty-three compounds were detected in the condensate of smoke produced by pyrolysis of cellulose. These compounds included furans, cyclic ketones, lactones, benzene derivatives, aliphatic ketones, and aldehydes. One of the major products was 2-hydroxy-3-methyl-cyclopenten-l-one. 

Another possibility is that both nitrogen atoms react with a double alkylating agent. In this way fused pyrazole derivatives (pyrazolo[l,2-a]pyrazoles) like (237) can be obtained by reaction of 3,5-dimethylpyrazole with 1,3-dichloropropane or l-chloro-3-propanol (69BSF2064). More surprising is the reaction with a-chlorocarbonylphenylketene which yields the paraionic compound (238) (80JA3971) which can also be obtained from 3,5-dihydroxy-4-phenylpyrazole and /3-dicarbonyl compounds (82JOC295). 

In a preliminary communication, the dihydroxy-1,2,4-triazine derivative 163 has been assigned the structure shown on the basis of infrared evidence. The pK and ultraviolet and infrared spectral data support the formulation of 6-azauracil (164) as a dioxo compound. 

The cyclic dimeric borazine derivatives 2 and 3 can be prepared by reaction of 2,4-dichloro-l,3,5,6-tetramethylborazine with aromatic 1,3-dihydroxy and l-amino-3-hydroxy compounds (Fig. 2). The products are obtained in yields... 

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