Diol monoethers

In the presence of BF3-OEt2, allyldimethylsilyl enolates react with acetals to give allylated 1,3-diol monoethers.139 A similar tandem aldol-allylation reaction can be performed by strained allylsilyl enolates such as 26 without promoter (Equation (34)).140 Allylsilanes bearing a vinyl ether moiety at the /3-position give rise to another type of tandem aldol-allylation reaction in the presence of a Lewis acid.141... 

In the first purely synthetic application of the reaction, Schreiber employed the 1,2-Wittig rearrangement to synthesize 1,3-diol monoethers (equation 15). The syn products (56) were obtained in 14—32% yield with 90-95% diastereoselectivity (Table 3). The 1,4-product (57) was found to predominate at low temperature, whereas at 0 °C the 1,2-product was favored but the absolute yield did not increase. 

Reductions of a)S-unsaturated oxo-compounds with sodium borohydride may be complicated by saturation of the ethylenic bond, and by base-catalysed conjugate addition of alkoxide to give a 1,3-diol monoether. The factors controlling these reactions have been studied for a variety of aliphatic compounds, and the findings may prove useful in steroid chemistry. ... 

The remarkable lability of the methoxyl group of aconitinone which is eliminated as methanol is clearly due to the newly formed carbonyl group and has been explained (51) as due to the presence in one ring in aconitine of a 1,3-diol monoether, converted by oxidation into a 8-methoxyketone (aconitinone), and thence into the a,/3-unsaturated ketone (aconitoline). 

Lithium tetrahydridoaluminate I lithium iodide 5 11-1,3-Diol monoethers from p-alkoxyketones... 

Alkoxyacoxy compounds from ) -ketoacetals via ) -hydroxyacetals and 1,3-diol monoethers... 

The lithium 2-butenyl(triethyl)aluminate complex, prepared in situ from 2-butenyllithium and triethylaluminum, displayed poor diastereoselectivity in a reaction with benzaldehyde (anti/syn 56 44)7. (Z)-3-Alkoxy-substituted aluminate complexes such as A-C, however, give good diastereoselectivity in aldehyde addition reactions8. The reactions of A with aldehydes at —100 °C give the jyw-diol monoether with >95% diastereoselectivity and >80-95% regiose-... 

Dioxacycloalkanes In the case of 1,3-dioxacyloalkanes, there are two possibilities for the rupture of the C-O bond. Esters or diol monoethers can be prepared depending on the regioselectivity of the bond rupture (Scheme 4.11). 

On Pt, Pd, Ni, and Rh the regioselectivity depends on the conditions. Mainly ester is formed at low hydrogen pressures, whereas mainly diol monoether is formed at higher pressures.30 31 Selectivity is structure-sensitive more ester is formed on highly dispersed catalysts. 

T. Iida, N. Yamamoto, N. Matsunaga, H.-G. Woo, M. Shibasaki, Enantioselective Ring Opening of Epoxides with 4-Methoxyphenol Catalyzed by Gallium Hetero-bimetallic Complexes An Efficient Method for the Synthesis of Optically Active 1,2-Diol Monoethers, Angew. Chem Int. Ed. EngL 1998,32 2223-2226. 

Olah et al.724 have shown that Nafion-H induces the ring opening of oxiranes under mild conditions to afford various products. Substituted oxiranes undergo hydrolysis or alcoholysis to yield 1,2-diols or 1,2-diol monoethers, when treated with Nafion-H under mild conditions in the presence of water or alcohols, respectively. Cycloalkene oxides give the corresponding trans products stereoselectively [Eq. (5.273)]. 

Optically active anti-1,2-diols.2 syn-1,2-Diols are available by addition of various y-alkoxyallylmetal reagents to aldehydes. In contrast, this reagent reacts with aldehydes to form anti-1,2-diol monoethers, which can be oxidized to the diol. In contrast, the reaction of 1 with some chiral aldehydes can show high enantioselectiv-... 

Bicyclic systems have provided an interesting framework for examination of stereochemical preferences in the rearrangements of diol monoethers. Monti et al. found that the anti (double bond and hydroxy group) isomer of the [2.2.2] bicyclic substrate (49) gave (50) stereospecifically, whereas the syn isomer gave a mixture of products (equation 27). 

Epoxide opening. Optically active trans-1,2-diol monoethers are readily obtained by the catalyzed reaction of epoxides with alcohols in the presence of the BINOL complexes and molecular sieves 4A. Similarly, p-hydroxy sulfides are formed. ... 

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