4-Chloro-benzene-1,2-diol

In a rather obscure, but synthetically very useful reaction, the biooxidative hydrox-ylation of chloro-benzenes (equation 23) has been used as a key step in the synthesis of inositols124. Cyclohexadiene c -diols are produced and similarly functionalized compounds may also be obtained from quinolines and isoquinolines125. These reactions have been exploited for the synthesis of a number of natural products126,127. 

Almost no 9,10-diaIkoxyphenanthrenes are known, and the quantities of those few made by other methods are either small or unstated. The best alternative procedure gave 9,10-dimethoxyphenanthrene when 9,10-phenanthrenequinone was combined first with sodium in diglyme and then with dimethyl sulfate, but the yield after two chromatographic purifications was 51 %. The only other reported alkylations of phenanthrene-9,10-diol are by 1-chloro-2-diethylaminoethane in 10% yield, f and by l,2-di(bromomethyl)benzene in 22% yield. s Unlike the procedure recorded here, none of these employ two-phase alkylations catalyzed by phase transfer agents." ... 

A solution of compound 182 (55.3 mg, 0.13 mmol) [Eq. (13)], (bromomethyl)chloro dimethyl silane (23 p,L, 0.17 mmol), and triethylamine (35 p,L, 0.26 mmol) in 1 mL of dry CH Clj was stirred for 3 h at room temperature, and then the solvent was evaporated under reduced pressure. The residue was rapidly eluted from a column of basic silica gel (hexane-EtOAc, 3 1) to afford an unstable syrup. This silyl ether was dissolved under argon in 2 mL of dry degased benzene. This solution was heated under reflux, and a solution of tributyltin hydride (56 mg, 0.2 mmol) and AIBN (2%) in 1 mL of benzene was added dropwise over 1 h. The heating was continued for 3 h, and benzene was evaporated. Methanol (0.2 mL), THE (0.2 mL), 30% HjOj (0.3 mL), and NajCOj (16 mg) were added to the residue. The mixture was refluxed for 4 h. Evaporation and column chromatography (hexanes-EtOAc, 1 1) gave the diol 60 (40 mg, 71%) as a gum [a]j, —12° (c 1, CHCI3). 

Butynediol can be selectively hydrogenated to c s-2-butene-l,4-diol in trifluoroeth-anol at - 20°C or in benzene-CF3CH20H at 0°C with tris(triphenyl-phosphine)chloro-rhodium(I) , or with IrCl(CO)(PPh3)2 as catalyst in toluene-trifluoroethanol at 60°C under weak UV irradiation ... 

In a 250-mL, three-necked flask attached to a short-path distillation apparatus, under argon, 40 mL of abs. benzene is added dropwise to ca. 3 mmol of the chiral diol (and, if necessary, 3 mmol of an alcohol . Then, 10 mL of benzene is distilled off. After addition of an equimolar amount of chloro(triisopropoxy)titanium in pentane, first pentane, then j-PrOH/benzene and finally (except for a small residue) benzene are distilled off, The yellowish residue is partially dried under high vacuum. 

Neopentane diol condenses with phosphorus trichloride in a manner analogous to (6.914) to give 2-chloro-5,5 -dimethyl-l,3,2 dioxaphosphinane. This latter compound is converted into the ethoxy derivative by a mixture of ethanol and pyridine, and it is oxidised in benzene solution to the oxychloride. Other reactions of the diol are indicated in the below scheme. 

Chloro-2-butyne-l-o1 - The procedure of Bailey and Fuji-wara (24) but replacing benzene with dichloromethane, gave a 50% yield, b.p. 70°C (20 mm Hg) from technical grade 2-butyne-l,4-diol (Aldrich). 

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