摘要:

AbstractThe phosphite triester (6), theO,O,O‐thiophosphate triester (7), and the phosphate triester (8) of methyl β‐d‐ribopyranoside were prepared. Crystal structures of6and7were determined by X‐ray diffraction. Quantum‐chemical calculations were performed on6. They clearly demonstrate that the positive charge on phosphorus is relatively high. This high charge is a result of the strain in the ester

ISSN:0165-0513    

DOI:10.1002/recl.19790981102

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractA polarographic study of the electro‐reduction of acetophenone in dry acetonitrile has revealed that under strictly anhydrous conditions the carbonyl compound can be reduced only if tetraalkylammonium ions are present. The role played by these ammonium ions is discussed. It is concluded that the catalytic effect of the ammonium ions has to be related to an increased polarization of the carbonyl double bond being induced during collision of the ammonium ions with the carbonyl compound. At high ammonium ion concentrations, however, the effect of this catalysis becomes smaller due to preferential adsorption of the ammonium ions on the electrode surface, as a result of which the carbonyl compound is displaced from the direct vicinity of the electrod

ISSN:0165-0513    

DOI:10.1002/recl.19790981103

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractSeveral alkyl aryl ketones have been electro‐reduced in an aprotic medium in the presence of tetraalkylammonium conducting salts. Quantitative yields of the corresponding pinacols have been obtained, except in cases where steric crowding in the starting ketone hampers the pinacolization. When chiral conducting salts are used considerable levels of enantiomeric excess in the (RS+SR) fractions of the pinacols are achieve

ISSN:0165-0513    

DOI:10.1002/recl.19790981104

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractThe preparation of the complementary oligodeoxyribonucleotidesIa,bandIIviaa modified phosphotriester method is described. The synthesis of these compounds was accomplished by using: (a) the levulinyl group for temporary and persistent blocking of the 5′‐hydroxyl; (b) the monofunctional phosphorylating agent 2,2,2‐trichloroethyl 2‐chlorophenyl phosphorochloridate (3) to introduce the phosphate moiety at the 3′‐position; (c) the benzoyl group to protect the terminal 3′‐hydroxyl; (d) acyl groups for the protection of the exocyclic amino functions of the bases; and (e) 1‐(2,4,6‐triisopropylbenzenesulphonyl)‐3‐nitro‐1,2,4‐triazole (TPS‐NT,11c) as activating agent in the formation of phosphotriester linkages. Final removal of all protecting groups was performed by fluoride ion treatment followed by aqueous ammonia. The oligonucleotidesIa,bandIIwere, after purification, isolated in good yields and, as followed from

ISSN:0165-0513    

DOI:10.1002/recl.19790981105

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractThe rate of the Schmidt reaction at 20°C has been determined for a variety of substituted benzoic acids. It is shown that electronic effects of substituents affect the reaction rate, electron donation increases the rate and electron withdrawal decreases it.Orthosubstituents accelerate the reaction, and the reaction is a good example of steric assistance. The buttressing effect of atert‐butyl group on an adjacent halogen atom is demonstrated in the high reaction rate of 2‐halogeno‐3,5‐di‐tert‐butylbenzoic acids. An attempt has been made to separate the effect of anorthosubstituent into steric, inductive and mesomeric contributions. A discussion on the mechanism of the reaction

ISSN:0165-0513    

DOI:10.1002/recl.19790981106

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19790981101

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY