Diols, preparation

This conversion has been used as a key step in the preparation of optically active aziridines from optically active 1,2-diols (prepared by 15-46). ° Even hydrogen can be the leaving group. Benzylic hydrogens have been replaced by N3 by treatment with HN3 in CHCI3 in the presence of DDQ (p. 1511). °°... 

The incorporation of two nonidentical chiral residues, each supporting C2 symmetry, into a mactocyclic poly ether affords a chiral crown compound with C2 symmetry provided its structure is constitutionally symmetrical. Thus, base-promoted reaction of the half-crown diol prepared from (5)-birraphthol with the half-crown ditosylate d-72 synthesized tom diacetone-manrritol affords (144) the 20-crown-6 derivative (S)-d-113 with C2 symmetry. When d-72 is condensed in like fashion with (/ 5)-binaphthol, then the diastereoisomeric 20-crown-6 derivative (/ )-d-114 can be separated chromatogiaphically tom (S)-d-113. In this matmer, (/ 5)-binaphthol is resolved by the carbohydrate unit during the synthesis. 

Oxidative cleavage of syn-diols preparation of ketones and aldehydes or carboxylic acids... 

Figure 8. Gel-permeation chromatograms of polu (propylene ether) diols prepared stepwise with Zn3[Co(CN)6]2 glyme ZnCk...

Scheme 20 Synthesis of polyester 20,20 by polycondensation of oc,co-diester and oc,co-diols prepared via SM of 10-undecenoic acid [123]...

A stoichiometric amount of 3f catalyzed the asymmetric aldol reaction of aldehydes with enol silyl ethers and subsequent asymmetric reduction, in one pot, to afford syn 1,3-diols with high enantioselectivity (Eq. 49) [43b]. With a variety of aldehydes, 1,3-diols were obtained in moderate yields (53-70 %) with high syn diastereoselectivity. The syn 1,3-diols prepared from aliphatic aldehydes in the reaction (in EtCN as sol-... 

Other unsymmetrical diols, prepared (inefficiently) by the coupling of mixtures of ketones, have been studied. The preferred cation argument is also found to be applicable to mixed medium-ring analogs, i.e. the kinetically favored pinacol rearrangement product is that predicted by consideration of the relative stabilities of the two possible, initially formed, carbocations. ° Earlier work with these compounds may have given misleading results due to product instability. To illustrate, Mundy observed that (24) is converted to (25) as the temperature is increased. 

All the compounds i, ii, and in were isolated during the years 1912- 1914, the last two being the first cyclic silicon polymers to be characterized. The first dialkylsilanediol was prepared in 1946 by the hydrolysis, by weak alkali, of (C2Hs)2SiCl2 it is a stable crystalline solid. Later, (CH3)2Si(OH)2 was prepared by the hydrolysis of (CH3)2Si(OCH3)2 as a crystalline solid extremely sensitive to acid or alkali, which cause condensation to polysiloxanes, mostly the cyclic tri- and tetra-compounds. Other diols, prepared include the n- and iso-propyl and butyl, and tert-butyl compounds, in addition to tetramethyldisiloxane-l,3-diol (iv). No silanetriol RSi(0H)3 has been isolated. 

Materials. 4-[(2-Hydroxyethyl)amino]-2-(hydroxymethyl)-4 -nitroazobenzene (T-AZODIOL) (10) was used as the NLO chromophore whose dipole moment is aligned transverse to the main chain. T-AZODIOL was synthesized via two step reactions as shown in Schemes 1 and 2. As shown, 3-(2-hydroxylamino)-benzylalcohol (DIOL) prepared from w-aminobenzyl alcohol with 2-chloroethanol was coupled with diazotized / -nitroaniline to give rise to T-AZODIOL. The details of the synthetic procedures were previously reported (8). 4-[N-(2-Hydroxyethyl)-N-methylamino]-3 -(hydroxymethyl)-azobenzene (AZODIOL) dye was the NLO chromophore monomer for preparing the polymer with NLO chromophore incorporated in the main chain. Detailed synthetic procedures of AZODIOL were previously reported (5), Commercially available 2,4-tolylene diisocyanate (TDI) and 4,4 -diphenylmethane diisocyanate (PDI) were used without further purification. The chemical structures of these monomers are shown in Figure 1. 

The importance of monol content in 4,T-MDI/BDO cured elastomer systems was determined by comparing 4000-MW PPG diols prepared via ultra-low monol technology, DMC and potassium hydroxide. They are designated as ultra-low monol, low monol and conventional and have monol contents of 0.005,0.016 and 0.085 meq/g, respectively. This corresponds to functionalities of 1.98, 1.94 and 1.71. We prepared 6% NCO 4,4"-MDI prepolymers and chain extended with BDO at an isocyanate to hydroxyl ratio (NCO OH) of 1.03 [15]. Table 9.3 summarises the monol effect on elastomer processing characteristics (pot life and demould time), and physical properties. 

Caryophyllane-2,6-a- and -P-oxides have been prepared from (— )-isocaryophyll-ene. Intramolecular epoxide opening has been studied for seven diols prepared by oxidation of the exocyclic double-bond of caryophyllene and isocaryophyllene epoxides. ... 

Emke, a., D. Hands, J. M. Midgley, W. B. Whalley, and R. Ahmad Unsaturated steroids. Part 6. A Route to Cholesta-5,7-diene-la,3P-diol Preparation of Steroidal 4,6,8(14)-Trienes. J. Chem. Soc. Perkin I 1977, 820. 

Preparation of Alcohols via Reduction Preparation of Diols Preparation of Alcohols via Grignard Reagents... 

The tricyclic amines (81 R = Me, Ph, COMe) fragmented when refluxed in aqueous base to give N-substituted 3-aminomethyl-7,7-dimethylcyclo-octane-l,5-diones. Treatment of the bisdibromocarbene adduct of cyclohexa-1,4-diene-1,5-diol (prepared by hydrolysis of the bisdibromocarbene adduct of the corresponding bis (methoxymethyl)ether) with pyridine gave the cyclo-octatrienone (82) whereas the isomeric bisdibromocarbene adduct of cyclohexa-1,4-diene-1,4-diol, gave only a low yield of benzocyclobutenone (83). ... 

Figure 7.9. The mass spectrum of the trimethylsilyl ether derivative of the vicinal diol prepared from methyl...

Figure 10. Gel permeation chromatogram of commercial poly(propylene ether) diol and diols prepared using zinc hexacyanocobaltate complex...

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