摘要:

Azo‐bridges of Azines. X. A New Way to Carbocyclic with Parallel Neighbouring NN/CC‐BondsNitrogen extrusion from the easily accessible triazoline11on acidic solid phases results in the formation of aziridine13together with14, a new system with parallel NN/CC‐bonds. By irradiation14undergoes smoothly [2 + 2]‐cycloaddition forming the cage compound15. Photolysis of11does not yield13or14. Instead by loss of the azo‐group either triazoline16or aziridine17are formed, depending on the band width

ISSN:0021-8383    

DOI:10.1002/prac.19903320202

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

Pyrroles from Methyl 3‐Amino‐3‐arylazo‐propenoat and α‐Halogenocarbonyl Compounds and the Forming of the Pyrrolo[3.2‐e][1,2,4]‐triazin Ring SystemMethyl 3‐amino‐3‐(2,4,6‐trichlor‐phenylazo)propenoat (2) and α‐halogenocarbonyl compounds (4a–c) undergo cyclization to pyrroles on the pattern of the Hantzsch‐pyrrole‐synthesis. The 2‐(2,4,6‐trichlor‐phenylazo)‐3‐pyrrolecarboxylic azide (7) reacts under Curtius rearrangement and cyclization to the ring syst

ISSN:0021-8383    

DOI:10.1002/prac.19903320203

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

On the Existence of 2‐Imino‐2H‐1,3‐thiazinesThe title compounds2are readily liberated from the 2‐amino‐1,3‐thiazinium salts1by treatment with bases. Their stability depends sensitively on the substituents at the imino‐N. The imino‐N substituted2a–iare isolable as well‐defined coloured substances. Reaction of the2as well1with nucleophilic agents affords pyrimidine‐2‐thiones (4,9–11,16–18). In these ring transformations a nucleophilic addition at ring position 6 as primary reaction step is preferred. The imino‐N unsubstituted representatives display a more complicated behaviour; the highly enhanced reactivity prevents or handicaps, respectively, any isolation. As exemplified in the base‐induced ring‐transformation of1 mto the pyrimidine derivative19, these2are able to react as nucleophiles too, and versatile intermolecular self

ISSN:0021-8383    

DOI:10.1002/prac.19903320204

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe chemiluminescent decomposition of functionalized 1,2‐dioxetanes was examined in toluene solution. Activation energies were measured by isothermal and nonisothermal kinetic methods. Quantum efficiencies were determined by Stern‐Volmer kinetics, using the fluorescers 9,10‐dibromo‐ and 9,10‐diphenylanthracene for the triplet and singlet excitation yields. The derivatives of 3‐hydroxymethyl‐3,4,4‐trimethyl‐1,2‐dioxetane (1a) have free energies of activation (ΔG≠) of ca. 25 kcal/mol, but the ΔG≠values of the annelated benzofuran‐type dioxetanes (5) are ca. 1 kcal/mol lower. There exists a reasonable correlation between the free energies of activation (ΔG≠) for the thermal decomposition of the dioxetanes and their

ISSN:0021-8383    

DOI:10.1002/prac.19903320205

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractStarting with the racemic aldehyde4, prepared from the tris(trimethylsilyl) ether3, the possibility was demonstrated of converting a trimethylsilylated primary hydroxy group with high selectivity into an aldehyde group in the presence of two trimethylsilylated secondary hydroxy groups employing oxalyl chloride and dimethyl sulfoxide (Swern reagent) as oxidant. The alkynylation of this aldehyde with 1‐metalated hept‐1‐yne afforded a chromatographically separable mixture of two diastereomeric alcohols, both being suitable intermediates for the synthesis of PGF2α. The diastereofacial selectivity of the addition strongly depends on the metal employed. Hept‐1‐yn‐1‐yllithium afforded a 67:33 mixture of (13 R*)‐ and (13 S*)‐alcohol, hept‐1‐yn‐1‐yltriisopropoxytitanium

ISSN:0021-8383    

DOI:10.1002/prac.19903320206

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe bleaching activators 1,5‐diacetyl 2,4‐dioxo‐hexahydro‐1,3,5‐triazine (DADHT), tetraacetyl ethylenediamine (TAED), tetraacetyl glycolurile (TAGU), N,N′‐diacetyl N,N′‐dimethyl urea (DDU) and pentaacetyl glucose (PAG) are efficient acetylating agents which convert primary and secondary amines into their N‐acetyl derivatives. The rates of the reactions of the bleaching activators mentioned with piperidine were determined in the temperature range 20 to 90°C using dioxane as the solvent. The kinetic constants can be regarded as rough measures of the activity of the

ISSN:0021-8383    

DOI:10.1002/prac.19903320207

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

Synthesis of Mustard Oil Oxides with Different SubstituentsTreatment of N‐alkyl‐N′‐aryl‐thioureas with chlorocarbonylsulfenyl chloride leads to 2‐alkyl‐4‐aryl‐3‐thiono‐1,2,4‐thiadiazolidin‐3‐ones (4). Isomerization of4takes place in the presence of strong acids to give 5‐alkylimino‐4‐aryl‐1,2,4‐dithiazolidin‐3‐ones (5). 5‐Arylimino‐4‐aryl‐1,2,4‐dithiazolidin‐3‐ones with different aromatic substituents (13a–e) are accessible by desulfurization of the corresponding 5‐arylimino‐4‐aryl‐1,2,4‐dithiazolidin‐3‐thiones (12) with benzonitril oxide. Structure of4follows both from desulfurization

ISSN:0021-8383    

DOI:10.1002/prac.19903320208

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractOxidative cleavage of 1,2:5,6‐di‐0‐cyclohexylidene‐D‐mannitol (2) with lead (IV) acetate yields (R)‐2,3‐0‐cyclohexylideneglyceraldehyde, which was transformed by oxidation and esterification into methyl 2,3‐0‐cyclohexylideneglycerate. Grignard reaction with various alkylmagnesium halides followed by acid‐catalyzed removal of the acetal group and reaction with p‐toluenesulfonyl chloride in pyridine furnished the title compounds (8a–d) in good chemical overall yield and high enantiomeric purity. The compounds were prepared as intermediates for the synthesis of a series of steroids w

ISSN:0021-8383    

DOI:10.1002/prac.19903320209

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

Synthesis and Reactions of N‐Phthalimido‐ketene‐S,S‐acetalsN‐substituted phthalimido derivatives1a–freact in the presence of bases (NaH, t‐BuONa) with carbon disulfide to the N‐phthalimido‐ketene‐S,S‐acetals3,4,5and6, respectively. 2‐Amino‐ketene‐S,S‐acetals7a–care formed by reaction of3a,bor5awith hydrazine hydrate.3cproduces with phenylhydrazine the pyrazole8, and with piperidine and pyrrolidine the E/Z mixture of the corresponding ketene‐S, N‐acetals9a,b.1cis transformed into10a–c(E/Z‐mixture)by treatment with phenylisothiocyanate under

ISSN:0021-8383    

DOI:10.1002/prac.19903320210

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

Thiatriazoles. VII. 3‐Aroxy‐1,2,4‐dithiazole‐5‐imids of 5‐Amino‐1,2,3,4‐thiatriazoleThe unstable but isolable 3‐aroxy‐1,2,4‐dithiazole‐5‐imids (2a–d) has been found on chlorothioformate acylation of 5‐amino‐1,2,3,4‐thiatriazole (1) in acetonitril. Further acylation and nucleophilic displacement reactions gave stable 3‐amino‐5‐acylimino‐1,2,4‐dithiazoles (6a–c,7). The structure of the prepared compounds was inferred from their1H and13C‐n.m.r., mass spectra and corroborated by comparison with the data of

ISSN:0021-8383    

DOI:10.1002/prac.19903320211

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY