Monoalkylation diols

Treatment of the boronate with Bui, AgO affords the monoalkylated diol in a manner similar to stannylene-directed monoalkylation and acylation. ... 

Reductive alkylation of -caprolactone (1 equiv) with a 2 0.25 mixture of Grignard reagent and Zn(BH4)2 affords monoalkylated diols, which can be further selectively oxidized with tetrapropylammonium perruthenate (TPAP) into the expected monoalkylated lactones <2002CR571>. 

The reaction of diols with alkylating agents can also be performed such that approximately the theoretical amount of monoalkylated product is obtained. Some substrates can even be monoalkylated [36, 41, 42] or monoarylated [43] with substantially higher yields than statistics would predict what must be due to the slowness of the second alkylation. This behavior, however, is not usually observed, and other strategies must usually be used to achieve clean monoalkylations. Use of excess diol will often furnish pure monoalkylated diol, but a suitable means of removal of excess diol will be required. In the examples sketched in Scheme 10.10 the products were purified by column chromatography, recrystallization, or distillation. As with acylations, the formation of monoalkylated diols can also be promoted by Ag20 [44] or by transient protection with boron [45] or tin [46] derivatives. 

An elegant strategy for the preparation of monoalkylated 1,2- and 1,3-diols is the nucleophilic ring-opening of cyclic acetals by hydride or by other nucleophiles (Scheme 10.12) [46, 56], Not all acetals undergo these reactions cleanly, and careful... 

Regioselective monoalkyl ether formation from naphthalene-1, 4-diols using alcohols (prim, or sec.) containing HCI. 

Selective monoprotection of diols is moderately effective. Fluoride ion-promoted monoalkylation of tartrate diesters that have been activated as the stannylene acetal is an extremely effective method for the efficient monoalkylations of diols. An equimolar mixture of dimethyl tartrate (la) and dibutyltin oxide in toluene, heated under reflux to azeotropically remove the formed water, provides a stannylene acetal. The crude acetal in DMF is treated with cesium fluoride and then benzyl bromide to provide in 85% yield the dimethyl (2J ,37 )-2-0-ben-zyltartrate (421). Reaction of la with benzyl bromide and CsF in DMF proceeds to provide 421 in only 5% yield. Benzyl iodide is generally a better alkylating agent, providing 421 in 99% yield [147]. 

Waterborne polyurethane resins are produced from maleinised monoglyceride (MMG) of sunflower oil, hydroxy-terminated polybutadiene, toluene diisocyanate and ethylene diamine. The carboxylic acid groups of MMG are neutralised by triethyl amine, making the resin water dispersible. The monoalkylated castor oil (MCO) or dehydrated castor oil (DCO) is treated with a polyether glycol at 120°C, followed by the addition of IPDI and DBTDL. To obtain a series of aqueous polyurethanes, butane diol and dimethylol propionic acids (DMPA) are added and the mixture heated to 70°C for two hours to produce a NCO-terminated pre-polymer which forms salt with triethylamine, giving a water-soluble polymer. The reaction mixture is dispersed in water and a chain extender, ethylene diamine, is added. Two aqueous polyurethanes, MCPU and DCPU, are finally obtained from MCO and DCO, respectively. 

---