摘要:

AbstractThe condensation of mesitonitrile and dichlorocarbene in aqueous medium to 1,2,4‐triazepines has been studied. In all cases this cycloaddition isperiand regiospecific. Compounds with the unknown ring systems isoxazolo[5,4‐e]‐1,2,4‐triazepine and azirino[2,1‐g]‐1,2,4‐triazepine have been synthesized. The structural elucidation of these products was accomplished by spect

ISSN:0165-0513    

DOI:10.1002/recl.19851040502

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe NADH models, (1R)‐1,4‐dihydronicotinamide and (1R)‐1,4‐dihydroquinoline‐3‐carboxamide (1‐4, R = X‐benzyl or octyl), are readily oxidized by methylene blue (MB⊕), yielding the corresponding pyridinium ions and leuco‐methylene blue (MBH). Under aerobic reaction conditions, molecular oxygen, present in the reaction solution, rapidly reoxidizesMBHtoMB⊕, thereby allowing the study of the oxidation of the NADH models under pseudo‐first‐order reaction conditions. In order to elucidate the mechanism of the oxidation of the NADH models byMB⊕, the influence of theMB⊕concentration, solvent and temperature has been studied as well as the effect of substituent variation in the benzyl group in a series of 1‐(X‐benzyl)‐1,4‐dihydronicotinamides (1a‐f). For one of the model compounds, 1‐benzyl‐1,4‐dihydronicotinamide (1a,BNAH), the primary and the secondary isotope effect and the temperature dependence of the kinetic isotope effect have been determined. It is concluded that oxidation of theNADHmodels byMB⊕most likely proceeds by a rate‐determining hydride transfer process via

ISSN:0165-0513    

DOI:10.1002/recl.19851040503

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe reagent 2‐chlorophenyl bis(1‐benzotriazolyl) phosphate has been used for the preparation of 5′‐O‐(methyl phosphate) esters of the dimers TpT, UpU, Upm26A and m26ApU, as well as 3′,5′‐bis‐O‐(methyl phosphate) esters of uridine (U) and the minor ribonucleosideN6,N6‐dimethyladenosine (m26A). A convenient synthesis of a non‐terminal (9) and a terminal (10) building unit o

ISSN:0165-0513    

DOI:10.1002/recl.19851040504

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractCyclopropylidenecyclohexane undergoes the ene reaction with singlet oxygen. The migrating allylic hydrogen originates exclusively from the cyclohexane ring and therefore the hydroperoxy group becomes attached to the cyclopropane ring. Since the O ‐ O bond in cyclopropyl peroxy systems is weak, the reaction product undergoes homolysis even at − 50°C and this also triggers rupture of the small ring.The resulting radical pair, consisting of7and the hydroxyl radical, recombines to form unsaturated β‐hydroxy ketone8and the di‐α, β‐unsaturated ketone9(cf. Scheme 2).As a model for a cyclopropylidenecycloalkane containing no active allylic hydrogen, the adamantyl derivative10was subjected to photo‐oxidation. In this case, the product is lactone11(yields in Table I), formed byearlyring enlargement,i.e.before O ‐ O rupture, as outlined in Scheme 4.The zwitter ion15aisomerises to the key intermediate carbonyl oxide17and, as a result of the presence of the cyclobutane ring, this can rearrange to lactone11in various ways (cf. Scheme 5 and 6). By photo‐oxygenation in18O‐labelled acetone, zwitter ion17is trapped by the solvent as an unstable ozonide which decomposes with formation of18O‐labelled lactone (Scheme 7). Photo‐oxygenation in the presence of TCNE gives exclusively ketone12by deo

ISSN:0165-0513    

DOI:10.1002/recl.19851040505

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19851040501

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY