William ether synthesis

Felcht UH (1985) Cellulose Ethers - synthesis, application and analytical aspects. In Kennedy JF, Phillips GO, Wedlock DJ, Williams PA (eds) Cellulose and its derivatives. Ellis Horwood Ltd, Chichester Tarvainen M et al (2004) J Control Release 96(1) 179 w w w. fiir. de/en/indexen.htm... 

UUmann ether synthesis. The original Ullmann ether synthesis9 involved melting the salt of a phenol with an aryl bromide in the presence of copper metal. Yields are low. Williams et al.10 found that the reaction can be carried out at lower temperatures by using as solvent pyridine, which forms a complex with copper salts (cuprous chloride preferred), which provides catalysis for the reaction reflux temperature is then sufficient. 

William s synthesis of a model compound of the dolastanes employed sodium naphthalide to induce the ring opening of the allylic ether, Eq. 146 [59]. Protonation at the y carbon gave the conjugated enone. 

Ben-Haida A, Colquhoun HM, Hodge P, Williams DJ. Synthesis of a catechol-based poly(ether ether ketone) (o-PEEK) by classical step-growth polymerization and by entrop-ically driven ring-opening polymerization of macrocyclic oligomers. Macromolecules 2006 39(19) 6467-72. 

Williams and Rastetter also accomplished an elegant synthesis of ( )-hyalodendrin (83) in 1980 [39]. Beginning with the sarcosine anhydride-derived enolic aldehyde 78, silyl protection of the enal enabled alkylation of the glycine center with benzyl bromide and thiolation using LDA and monoclinic sulfur a la Schmidt. After protection of the thiol with methylsulfenyl chloride and deprotection of the silyl ether, the enol was sulfenylated with triphenylmethyl chlorodisulfide to afford bis(disulfide) 82 as a 2 1 mixture of diastereomers favoring the anti isomer. Reduction of the disulfides with sodium borohydride and oxidation with KI3 in pyridine afforded ( )-hyalodendrin (83) in 29 % yield (Scheme 9.4). 

The same strategy has been used by Williams (90JA808) in his synthesis of brevianamide B. The aldehyde (82), prepared enantioselectively from L-proline, was converted to the silyl ether. Acylation of this (BuLi, ClC02Me) gave the carbomethoxy derivative as a mixture of diastereo-mers, which was alkylated by gramine. As before, an enolate alkylation (Sn2 ) on an allyl chloride derived from the above gave the tricyclic compound, which could be transformed to brevianamide B (Scheme 24). 

Acemoglu L, Williams JMJ (2002) Synthetic Scope of the Tsuji-Trost Reaction with Allylic Halides, Carboxylates, Ethers, and Related Oxygen Nucleophiles as Starting Compounds. In Negishi E, de Meijere A (eds) Handbook of Organopalladium Chemistry for Organic Synthesis. Wiley, New York, p 1689... 

Marchand et al. have reported the synthesis and X-ray structures of the cage-annulated oxa-thiacrown ethers 15 <2002JCX447>. Using these oxa-thiacrown ethers except for 15g and 15h, Williams et al. measured the electrospray ionization (ESI) mass spectrometry (MS) of the complexes with Hg2+, Pb2+, Cd2+, and Zn2+ cations <2002ANC4423>. All of the macrocycles in series bound the mercury ion very selectively and efficiently in the presence of many other metal ions. 

An intramolecnlar palladium-mediated allylic alkylation via a ketone enolate of piperidinone 54 was reported by Williams and coworkers for the synthesis of R)-l-hydroxyquinine 57 (eqnations 17 and 18) °. The key step involves a palladium-mediated Sjv2 -type cyclization reaction of enol ether 55 in the presence of BnsSnF, giving rise to a quinuclidine ketone, which was immediately rednced to 56 to avoid equilibration and /3-elimination. Interestingly, none of the undesired C3-vinyl stereoisomer was observed. 

The reduction of the p-acyloxy sulfone is most often carried out with sodium amalgam, as the examples below indicate. The reductive elimination can be buffered with disodium hydrogenphosphate for sensitive substrates. In certain applications it has proven advantageous to utilize lithium or sodium in ammonia. For example, Keck s synthesis of pseudomonic acid C made use of the lithium/ammonia reductive elimination to simultaneously form an alkene and deprotect a benzyl ether.In studies directed toward the same target, Williams made use of a reductive elimination procedure developed by Lythgoe, involving the formation of the xanthate ester followed by reduction with tri-n-butyltin hydride. ... 

For the Sonn-Miiller synthesis of o-tolualdehyde, Williams et al. prepared the imino chloride with benzene as solvent, distilled off the benzene and POCU, and dissolved the viscous residue in ether. A mixture of 0.26 mole of anhydrous stannous o Cl... 

Leaving groups in the Tsuji-Trost reaction include acetates, halides, ethers, carbonates, sulfones, carbamates, epoxides, and phosphates. Reviews (a) Tsuji, J. In Handbook of Organopalladium Chemistry for Organic Synthesis, Negishi, E. deMeijere, A., Eds. Wiley-lnterscience New York, 2002 Vol II, Palladium-Catalyzed Nucleophile Substitution Involving Allyl Palladium, Propargyl-palladium and Related Derivatives, pp. 1669-1687. (b) Frost C. G. Howarth, J. Williams, J. M. J. Tetrahedron Asymmetry 1992, 3, 1089-1122. 

The total synthesis of milbemycin-p developed by Williams et al. [124] involves construction of three units the spiroketal moiety (A), carbon chain with a remote chiral centre at C-12 (B) and the substituted benzoic acid (C). Unit (A) is prepared starting from citronellol (154), while unit (B) was prepared starting from (-)-(3S)-citronellal (162) (Scheme 20). A and B were joined after transmetalation of the tetrahydropyranyl ether 166 to give 167 (Scheme 21), which is allowed to react with the aldehyde A to give 168. Further steps are shown in scheme 22. 

Reduction of phenols [1, 252, after citation of ref. 3]. In achieving the synthesis of triptindane (11), Thompson obtained the methyl ether (8a) as an intermediate, demethylated it to (9), and effected deoxygenation to (11) by the method of Kenner and Williams consisting in reaction with diethyl phosphonate or mesyl chloride and reduction of the diethyl phosphate or the mesylate ester with sodium in liquid ammonia yields, first procedure 58% second procedure 36%. 

The PTAD-diene protected 22-aldehyde analog has been used by Williams and Eyley to synthesize 24,25-dihydroxy derivatives via an aldol reaction with the tetra-hydropytanyl ether of 3-hydroxy-3-methyl-2-butanone followed by NaBH4/pyridine reduction [scheme (9)] The same starting aldehyde is also a precursor for synthesis of the 25,26-dihydroxy-5,7-diene [scheme (10)] ... 

R Cl + RO-Na+ R OR + NaCl The product ether is termed mixed if the alkyl groups R and R are different. This synthesis can produce both simple and mixed ethers. The synthesis is named for the British chemist Alexander William Williamson (1824-1904). 

At the same time Alexander William Williamson (1824-1904) was trying to prepare higher alcohols by substituting the hydrogen in ethanol by an alkyl radical. When he reacted ethanol with potassium ethoxide, he found that instead of another alcohol he obtained diethyl ether. This synthesis meant that ethanol could not be the hydrate of ether as Liebig had proposed, and Williamson suggested the existence of a water type,... 

Alexander William Williamson was an English chemist who lived between 1824 and 1904. His method is especially useful for synthesis of unsymmetrical ethers. 

L. H. William, Ph.D. Thesis, Synthesis and characterization of sulfonated poly(arylene ether sulfone) copolymers via direct copolymerization candidates for proton exchange membrane fuel cells. Hampton University, Virginia, USA, 2002. 

Malus leaf. That it was an intermediate was indicated by its rapid conversion during chromatographic purification into chrysin 7-glucoside. More recently, a second dibenzoylmethane, namely the 2,6-dihydroxy-4-methoxy-derivative, was reported in Populus nigra buds. More careful examination of this latter material, however, showed it to have the isomeric cyclic structure of a 2-hydroxyflavanone, i.e. (29). This was proved by Lx., m.s., and n.m.r. studies and also by synthesis. Its co-occurrence in Populus buds with the 7>methyl ethers of galangin, chrysin, and pinocembrin suggests it has a biogenetic role. In retrospect, it seems likely that Williams compound in Malus has a similar cyclic structure [i.e. (30)] rather than the open-chain form. Re-examination of... 

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