Copper sulfate diols

The dehydration of ds-chroman-3,4-diols with copper sulfate or p-toluenesulfonic acid gives the chroman-3-one (68BSF4203), whilst pyrolysis of the chlorohydrin (615) yields the naphthopyran-3-one (Scheme 235) (67JCS(C)1472). 

In a first step, the TBS ether is subjected to acid cleavage with copper sulfate in acetone containing a catalytic amount of glacial acetic acid. The resulting diol is then protected as an acetunide. Next, the double bond is oxidatively cleaved with sodium periodate and a catalytic amount of osmium tetroxide to give aldehyde 5. 

A mixture of potassium permanganate and copper sulfate will oxidize sim de 1,4- and l,S-dioxidize selectively primary-secondary diols (21 equation 24) and (22 equation 2S) to the corresponding lactones. ... 

Isopropylidene derivatives of vicinal diols, for example glycerol ethers, 1-monoacylglycerols or dihydroxy acids, are prepared by reacting the diol with acetone in the presence of a small amount of an acidic catalyst (Figure 4.1(d)). Anhydrous copper sulfate is probably the mildest catalyst and is used as follows ... 

Estr-5(10)-ene-3a,17 -diol (10 g, 36.2 mmoles) is added over a period of 1 hr to a refluxing mixture consisting of 60 g (0.92 moles) of zinc-copper couple, 350 ml of dry ether and 180 g (54 ml, 0.67 moles) of methylene iodide. After the addition is complete, half of the solvent is removed by distillation and 200 ml dry ether is added. The reaction mixture is then transferred to a sealed stainless steel tube and maintained for 3 hr at 92° before being cooled in an ice bath and poured into 500 ml of saturated aqueous sodium bicarbonate solution. The resultant mixture is extracted with ether and the extracts are dried over anhydrous sodium sulfate and concentrated to yield a solid residue which gives 8.4 g (80%) 5,19-cyclo-5a,10a-androstane-3a,17) -diol mp 161-163° [aJo 40° (CHCI3), on crystallization from acetone. 

Obviously, the condensation of a carbonyl group with a diol produces 1 mol of water and because of the reversibility of the reaction (hydrolysis of the acetal), yields are lowered if this by-product is not removed. For such a purpose, there are essentially two possibilities (1) the continuous removal of water by an azeotropic distillation with a solvent mainly chosen for its boiling point (petroleum ether, benzene, toluene, xylene, for instance) (2) the presence of a desiccant (the most commonly taken is copper(II)sulfate, but sodium sulfate or molecular sieves have been also used) molecules known to be water scavengers, such as ortho-esters or dialkylsulfites, have also been suggested, even if they are seldom used in carbohydrate chemistry. 

The reaction of oxiranes with carbonyl compounds in the presence of Lewis acids is an efficient way of preparing 1,3-dioxolanes (81S501). The reaction, shown in Scheme 33, proceeds with inversion of stereochemistry of the oxirane. A diol does not appear to be an intermediate even in the presence of water. Many Lewis acid catalysts are effective, but the use of anhydrous copper(II) sulfate in an excess of the carbonyl compound as solvent probably offers the mildest conditions. Since the copper(II) sulfate is insoluble, the reaction appears to be truly heterogeneous in nature and the mixture must be well stirred (78JOC438). 

Hydration of aryl-substituted epoxides. Treatment of aryl-substituted oxiranes with copper(II) sulfate and pyridine in an aqueous phosphate buffer (pH 7) affords cis-diols by reaction of water at the benzylic position. Less than 15% of trans cleavage products obtain. In the absence of pyridine, the oxides are rapidly destroyed. Triethylamine cannot be substituted for pyridine. cis-Chlorohydrins are obtained when aryl-substituted oxides are treated with copper(II) sulfate, pyridine, and kiCl in THF, When methanol is used as solvent, the corresponding cis-glycol monomethyl ether is obtained. In all cases substitution occurs at the benzylic position. Alkyl oxiranes do not react under these conditions. ... 

C(S,v(c-DIOLS Copper(II) sulfate-Pyridine. ThalUum(l) acetate. 

---