Diol reactions

The first kinetic investion of the ethane-1,2-diol reaction was carried out by Price and Knell . However, these workers did not detect the typical mixed-order kinetics which were later established by Duke °, and investigated over a wide range of conditions by Buist and Bunton With excess diol Duke showed that the reaction is first-order with respect to periodate, and that the first-order rate coefficient k is a function of diol concentration, viz. 

Analyses were performed on a Varian 9010 instrument equipped with a Varian 9050 UV detector (210 nm) using a Merck Lichrospher 100 RP18 (5 tm) column. An aqueous nBu4NHS04 5mM (1 ml/min) as the eluent was used for ethane-1,2-diol reaction products... 

Stereoselective epoxidation of enoates. The final step in the synthesis of (+)-aphidicolin (4) requires a stereoselective conversion of the cyclic norketone (I) to a Wol,2-diol, >C(0H)-CH20H. Methylcnation of the ketone followed by a Sharpless asymmetric dihydroxylation provides a 1 1 mixture of epimcric 1,2-diols. Reaction with a chiral oxaziridinc also provides a 1 1 mixture of cpimcric epoxides. The transformation is effected successfully by conversion of the ketone to the enol triflate, which is converted to the enoate (2) by Pd-catalyzed carbonylation in methanol (13,234). Epoxidation of 2 with m-CPBA in buffered CH2CI2 with a radical scavenger (4,85-86) results in a single epoxy ester (3) in 90% yield. This product is reduced with lithium aluminum hydride (excess) to aphidicolin (4) in 67% overall yield from the ketone 1. 

There are many reactions that generate a mixture of syn and anti diastereomers, and if the reaction is diastereoselective, one predominates. In Chapter 9, we will see many examples of this in connection with enolate anion condensation reactions. An example is the conversion of alkenes to 1,2-diols. Reaction of... 

The avoidance of a-ketol by-products is an important feature of a new catalytic osmylation procedure for the preparation of cis-1,2-diols. Reaction involves treatment of the olefin with N-methylmorpholine iV-oxide dihydrate in aqueous acetone, and osmium tetroxide in t-butyl alcohol at 25 °C, overnight. Reduction (NaHS03), adsorption on to magnesium silicate, filtration, neutralization, and ethyl acetate extraction afforded the diols in moderate to excellent yield. An example is the synthesis of (397 55 %) from (396). 

The 1,4-isomer has been similarly generated from terephthalonitdle [623-26-7] (56) using a mixed Pd/Ru catalyst and ammonia plus solvent at 125 °C and 10 MPa (100 atm). It is also potentially derived (57) from terephthaUc acid [100-21-0] by amination of 1,4-cyclohexanedimethanol (30) [105-08-8], Endocyclization, however, competes favorably and results in formation of the secondary amine (31) 3-a2abicyclo[3.2.2]nonane [283-24-9] upon diol reaction with ammonia over dehydration and dehydrogenation catalysts (58) ... 

High-Molar-Mass Poly(tetramethylene octanedioate) by Diester—Diol Reaction... 

Acid anhydride-diol reaction, 65 Acid anhydride-epoxy reaction, 85 Acid binders, 155, 157 Acid catalysis, of PET, 548-549 Acid-catalyzed hydrolysis of nylon-6, 567-568 of nylon-6,6, 568 Acid chloride, poly(p-benzamide) synthesis from, 188-189 Acid chloride-alcohol reaction, 75-77 Acid chloride-alkali metal diphenol salt interfacial reactions, 77 Acid chloride polymerization, of polyamides, 155-157 Acid chloride-terminated polyesters, reaction with hydroxy-terminated polyethers, 89 Acid-etch tests, 245 Acid number, 94 Acidolysis, 74 of nylon-6,6, 568... 

Diacetoxybenzoic acid, synthesis and polymerization of, 116-118 Diacid, anhydride, and diol reaction, 97 Diacid chloride-diol solution reactions, 75-77... 

Diacid chloride methods, 182-183 Diacid chlorides, 333 Diacid-diol copolyesters, 43 Diacid-diol polyesterifications, 66 Diacid-diol reaction, 95-97 Diacid method, 180-181 Diacids... 

Diester-diamine polyamides, 157-158 Diester-diol enzyme-catalyzed solution reaction, 100-101 Diester-diol reaction, 98 Diester method, 181-182 V,lV-Diethylcyclohexylamine (DECHA), 229... 

Poly(ethylene adipate), synthesis by diacid-diol reaction, 95-97 Poly(ethylene isophthalate) (PEI) homopolyesters, 89-90 Poly (ethylene isophthalate-co-tere-phthalate) (PEIT), synthesis of, 106-107... 

Boronate/diol reaction Chemical stimulation (e.g., sugar) [32]... 

Synthesis and characterization of polyols. The procedure described above yields PHBA-modifled oligomers, apparently with minimal side reactions. The odor of phenol was barely detectable in the products, indicating that little phenol had been formed. p-TSA catalyst plays a crucial role. When p-TSA was not used in the 30/70 PHBA/diol reaction only 75% of theoretical distillate was collected, and the product smelled strongly of phenol. Solvent plays an important role by helping control temperature and by facilitating removal of water. If desired, the products can be purified as described to remove small amounts of unreacted PHBA and phenol. 

Most of the work on the boric acid-diol reaction during the last twenty years has been done to determine the coordination number of the diol (number of diol molecules) in the complex and to evaluate the equilibrium constant (often called a stability constant) for a number of diol-boric acid reactions. Several techniques have been used to study these questions, including polarimetry (7), optical rotatory dispersion (8), polarography (9), conductivity (3), vapor pressure osmometry (10), and electrochemistry (II, 12, 13). The most frequently studied system has been the electrochemical (pH) titration of boric acid or borax solutions with various diols. 

The Reactive Boroxy Species. Most of the previous work on the boric acid-diol reaction has included the assumption that a diol reacts with the borate anion and not with undissociated boric acid. Whether or not this assumption is correct in most cases would not have affected the general conclusions of the work. However, the assumption has been stated in most of the previous literature for one reason or another. 

Sugar Structure and the Boric Acid-Diol Reactions... 

It has proved possible to confirm (22) that it is the monoanion of the periodic acid that predominantly participates in the oxidation of the diols. Reactions of 1,2-diols of the type R1CH(OH)CH(OH)Ra (where R1 and R2 are alkyls or aryls) are generally acid-base catalysed (22) and there appears to be no accumulation of an intermediate, as has been shown... 

Alkenes from diols. Reaction of v/c-diols with two secondary hydroxyls or one primary and one secondary alcohol with chlorodiphenylphosphine (2 equiv.), imidazole (4 equiv.), and iodine (2 equiv.) results in alkenes. The reaction presumably involves a vic-iododiphenylphosphinate, which can be isolated in some cases and converted to an alkene with zinc in acetic acid. 

Q Use your knowledge of alcohol and diol reactions to propose mechanisms and products for similar reactions that are new. 

The p-hydroxy carbonyl compound formed from the crossed aldol reaction can be reduced with NaBH4, CH3OH (Section 20.4A) to form a 1,3-diol (Reaction [1]) or dehydrated to form an a,p-unsaturated carbonyl compound (Reaction [2]). Reduction of the c(,p-unsaturated carbonyl compound forms an allylic alcohol with NaBHi (Reaction [3]), or a ketone with H2 and Pd-C (Reaction [4]) see Section 20.4C. Reaction of the a,p-unsaturated carbonyl compound with an organometalllc reagent forms two different products depending on the choice of RM (Reaction [5]) see Section 20.15. 

---