摘要:

AbstractThe15N nmr spectra of a series of 1,2,3‐thiadiazoles reveal the strong influence of substituents at C‐5 on the N‐2 resonance. Upon methylation, the two thiadiazole nitrogen resonances are shielded, but the most dramatic shift is observed for the methylated nitrogen, Δδ>140 ppm. The15N chemical shifts of some mesoionic thiadiazoles were also determined and explained by the dual effect of 5‐substitution and salt formation. By disconnecting these effects, the15N chemical shifts of10and11were found to be unusual and to reflect a thiapentalene

ISSN:0022-152X    

DOI:10.1002/jhet.5570300201

出版商:Wiley‐Blackwell    

年代:1993

数据来源: WILEY

摘要:

AbstractEthyl 2,4‐dioxooctanoate (1) was selectively protected as the 2‐(methoxyimino) derivative2. When 2 was reacted with phenylhydrazine hydrochloride, ethyl 3‐butyl‐1‐phenyl‐1H‐pyrazole‐5‐carboxylate (4) was favored over the corresponding 5‐butyl‐1‐phenyl‐1H‐pyrazole‐3‐carboxylate product5by a ratio of at least 6:1, a complete reversal of the regioselectivity observed for1. The structures of4and5were assigned definitively by NOE difference experiments. Regiochemical and configurational assignments of the mono‐ and bis(methoxyimino) derivatives of1were also achieved

ISSN:0022-152X    

DOI:10.1002/jhet.5570300202

出版商:Wiley‐Blackwell    

年代:1993

数据来源: WILEY

摘要:

Abstract9‐Amino‐3‐(β‐D‐ribofuranosyl)pyrazolo[3,2‐i|purine (6) has been prepared from a fully protected 3‐(β‐D‐ribofuranosyl)pyrazolo[3,2‐i]purine (2) and the 9‐bromo substituted derivative3by nitration, followed by reduction. Reaction of 9‐bromo‐3‐(β‐D‐ribofuranosyl)pyrazolo[3,2‐i)purine (1b) with alkali gave the (pyrazol‐3‐yl)imidazole derivative, followed by diazocyclization with sodium nitrate to give 9‐bromo‐3‐(β‐D‐ribofuran‐osyl)imidazolo[4,5‐d]pyrazolo[2,3‐c][1,2,3]triazine (10) after deacetylation. Compounds

ISSN:0022-152X    

DOI:10.1002/jhet.5570300203

出版商:Wiley‐Blackwell    

年代:1993

数据来源: WILEY

摘要:

Abstract1,3‐Dipolar cycloadditions of stable 4‐azido‐6‐methyl‐2H‐pyran‐2‐one1with electron‐rich alkenes and alkynes lead to 4,5‐substituted 1‐(6‐methyl‐2‐oxopyran‐4‐yl)‐1,2,3‐triazoles. Iminophosphoranes derived from1have also been synthesized. 5‐Oxopyrano[4,3‐b]pyridines are prepared by reaction of 4‐amino‐6‐meth

ISSN:0022-152X    

DOI:10.1002/jhet.5570300204

出版商:Wiley‐Blackwell    

年代:1993

数据来源: WILEY

摘要:

AbstractThe potential anti‐cancer agent6has been synthesised from 4‐(4‐chlorobutoxy)‐2‐nitroaniline,15bby the conversion of the nitroaniline to the benzotriazineN‐oxide16. Theophylline has been reacted with16to give theN‐oxide9and this has been oxidised to the requiredN,N'‐dioxide,6. The compound6has been found to be ineffective as a

ISSN:0022-152X    

DOI:10.1002/jhet.5570300205

出版商:Wiley‐Blackwell    

年代:1993

数据来源: WILEY

摘要:

AbstractThe title compounds5are produced in the reaction ofN‐fluoropyridinium tetrafluoroborate (1) with sulfides2. The proposed mechanism involves single‐electron transfer from2to1followed by transformations of the resultant radical intermedia

ISSN:0022-152X    

DOI:10.1002/jhet.5570300206

出版商:Wiley‐Blackwell    

年代:1993

数据来源: WILEY

摘要:

AbstractDifferentN‐methylsubstituted,N'‐methylsubstituted andN,N'‐unsubstituted triazol‐1‐ylcarbothiohydrazides were reacted with isocyanates and isothiocyanates to yield the corresponding carbamoyl and thiocarbamoyl derivatives4. The thiocarbamoyl derivatives could be cyclised by heating in dimethylformamide or 10% sodium hydroxide solution, reacting them with dicyclohexylcarbodiimide or thier alkylation to the corresponding 1,3,4‐thiadiazoles12and16, and derivatives5formed by splitting the triazole moiety. Cleaved derivatives9and11were also formed in the reaction of thiocarbamoyl derivatives4with carbon disulfide in the absence or presence of methyl iodide, respectively. Spectroscopic evidence is given for the structure of produc

ISSN:0022-152X    

DOI:10.1002/jhet.5570300207

出版商:Wiley‐Blackwell    

年代:1993

数据来源: WILEY

摘要:

AbstractA series of substitutedN‐methylstyrylpyrroles (H,p‐Br,p‐CN,o,p‐diCl,m‐CH3,m‐CN,m‐NO2) were preparedviathe Wittig reaction of 1‐methylpyrrole‐2‐carboxaldehyde and substituted benzyltriphenylphosphonium bromides. Bothcisandtransisomers were found to be present in the reaction mixture and they were separable by column chromatography in a few cases (H,p‐Br,m‐CN,m‐NO2). Photochemical isomerizations ofcis‐styrylpyrroles totransisomers were observed when the substituents wereo,p‐diCl andm‐NO2, while the opposite was the case with compounds having H,p‐Br,m‐CH3,m‐CN. It was difficult to separate thecisandtransmixture ofp‐cyanostyrylpyrroles and the equilibrium ratio did not change under si

ISSN:0022-152X    

DOI:10.1002/jhet.5570300208

出版商:Wiley‐Blackwell    

年代:1993

数据来源: WILEY

摘要:

Abstract6aλ4‐Thia‐1,2,3,4,6‐pentaazapentalenes3are conveniently prepared by reacting 5‐imino‐Δ3‐1,2,4‐thiadi‐azolines2with aromatic diazonium tetrafluoroborates in the presence of pyridine. The first crystal structure analysis of this class of compounds3gis described and shows properties characteristic of a thiapentalene structure;i.e.long N‐S‐N bonds (1.85 and 1.975 Å) in a nearly linear arrangement (164°) and comprising a heterobicycle w

ISSN:0022-152X    

DOI:10.1002/jhet.5570300209

出版商:Wiley‐Blackwell    

年代:1993

数据来源: WILEY

摘要:

AbstractN‐Benzoylsaccharins,N‐(saccharinylmethyl) benzoates andN‐alkylsaccharins were synthesized fromN‐hydroxymethylsaccharin and the corresponding benzoyl chlorides or alkyl halides under different conditions. The reaction mechanisms are also di

ISSN:0022-152X    

DOI:10.1002/jhet.5570300210

出版商:Wiley‐Blackwell    

年代:1993

数据来源: WILEY