摘要:

AbstractIn this paper we report the synthesis of five retinals, specifically mono‐labelled with13C at the positions 1, 2, 3 and 4 and di‐labelled with13C at the positions 16 and 17, with more than 98% chemical purity and high13C incorporation. (1‐13C)‐ and (16, 17‐13C2)retinal were obtained in 20% overall yield from (2‐13C)‐ and (1,3‐13C2)acetone. (2‐13C)‐ and (3‐13C)retinal were prepared in 10% overall yield from (1‐13C)‐ and (2‐13C)acetonitrile, while (4‐13C)retinal was synthesized in 17% overall yield star

ISSN:0165-0513    

DOI:10.1002/recl.19891080602

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractTo diphenylglycoluril (2), four aliphatic chains were attached, each with a vanillyl alcohol group at the end. In an acid‐catalyzed reaction, three of the vanillyl alcohol groups cyclize to form a cyclotriveratrylene unit. The resulting compound (3) has a well‐defined cavity and a free, functionalized arm. Cyclization of four vanillyl alcohol groups (5) does not occur, probably for steric reas

ISSN:0165-0513    

DOI:10.1002/recl.19891080603

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractA solid‐phase synthesis of an aminohexyl‐containing hexameric fragment of theH. influenzaetype b capsular polysaccharide, using a phosphoramidite approach and controlled‐pore glass as the solid support, is rep

ISSN:0165-0513    

DOI:10.1002/recl.19891080604

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractStudies on benzylation of hydrophilic carbohydrate derivatives with benzyl chloride, using a phase‐transfer technique, have led to the conclusion that alkylation of a substrate can be greatly facilitated by the introduction of a “co‐catalyst” (e.g.a tertiary alcohol) and/or a co‐solvent (e.g.DMSO) to the reaction mixture. Efficient procedures for benzylation of sugar derivatives having three to eight hydroxyl groups per molecule, in a two‐phase system employing an almost stoichiometric amount of the alkylating agent, ar

ISSN:0165-0513    

DOI:10.1002/recl.19891080605

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractMeasurements of the static dielectric constant at 10 KHz, the refractive index (using a sodium light) and the complex dielectric constant at 9.34 GHz have been made for three substituted acetophenones in a dilute solution of benzene over the temperature range 30‐60 °C. Dielectric relaxation times τ(1) and τ(2) have been calculated using the single‐frequency concentration‐variation method as suggested byHigasi. Comparison with a few available results indicates that τ(2) leads to relaxation times for overall molecular rotation, whereas τ(1) becomes an explicit function of both inter‐ and intramolecular‐relaxation times. τ(2), as well as the distribution parameter (α), show a systematic decrease with increase in temperature. Values of the dipole moments are also reported for the

ISSN:0165-0513    

DOI:10.1002/recl.19891080606

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe1H NMRspectra of 3‐(triethoxysilyl)propanenitrile (1), 3‐(trichlorosilyl)propanenitrile (2) and trichloropropylsilane (3) show that these systems are present to about 40% in thegaucheconformer. For1and3, the solvent dependence of the conformational equilibrium has also been studied. In more polar solvents, the more polargaucheconformers contribute to a greater extent to the equilibrium mixture. The results ofMNDOcalculations for these compounds are compared with the conclusions drawn from theNMRzmeasurements. The reliability ofMNDOfor the description of this type of organosilicon compound is descri

ISSN:0165-0513    

DOI:10.1002/recl.19891080607

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe thermolyses in hydrogen of 3–6 vol. % of 1,1‐dichloroethene, (E)‐1,2‐dichloroethene, trichloroethene and tetrachloroethene have been examined in a tubular flow reactor at atmospheric pressure between 828 and 1068 K. Major products are HCl, lower chlorinated ethenes, ethyne, ethene, ethane and methane. Chlorinated benzenes, major products in the straight pyrolysis of these compounds, are formed in only small amounts, the reasons for which are discussed. Dechlorination occurs in part via a chain mechanism involving H‐atom addition andipsosubstitution of Cl. A second route, molecular elimination of HCl, also occurs but appears to become less important for the more chlorinated substrates. At 880 K, addition of a H atom to the monochloro‐substituted carbon of C2HCl3takes placeca. 8 × more rapidly than it does to the dichloro site. The hydrogen‐atom concentration is somewhat greater than that calculated from equilibrium dissociation of H2and varies by a factor ofca. 4 for the various substrates. Differences in hydrogen‐atom concentration are larger at lower temperatures, apparently due to the presence of relatively unreactive radicals in some systems, which lead to increased c

ISSN:0165-0513    

DOI:10.1002/recl.19891080608

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractA medium‐scale one‐pot synthesis of bis(trimethylsilyl)hexatriyne is described and the potential of this compound as a precursor of an organic superconductor (the “Little model)” is di

ISSN:0165-0513    

DOI:10.1002/recl.19891080609

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19891080610

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19891080613

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY