Cyclocondensation of alkylhydrazines and .beta.-substituted acetylenic esters: synthesis of 3-hydroxypyrazoles
摘要:
Addition of monosubstituted alkylhydrazines to acetylenic esters with either electron-withdrawing or sterically bulky beta-substituents afforded 1-alkyl-3-hydroxy-5-substituted-pyrazoles 1 as the major regioisomeric product. By comparison, the classical cyclocondensation of alkylhydrazines with beta-keto esters gives the regioisomeric pyrazol-5-ones 2. The reaction solvent employed in these cyclocondensations can have a profound effect on regioisomeric product ratios. Addition of methylhydrazine to 5g in methylene chloride gave regiospecific formation of pyrazolinone 2o, whereas addition in water-methanol mixtures afforded hydroxypyrazole 1o as the major product. Structural assignment of regioisomers 1 and 2 are based on C-13 NMR chemical shifts, long-range heteronuclear coupling constants, and comparisons with regiochemically known hydroxypyrazoles and/or pyrazolinones. Additions of acetylene 5b to 1,1-dimethylhydrazine afforded either acyclic enehydrazone 12 or pyrazolium betaine 13 depending on the reaction conditions.
DOI:
10.1021/jo00047a021
作为产物:
描述:
alkaline earth salt of/the/ methylsulfuric acid 在
三乙胺 作用下,
以41%的产率得到α-(pivaloyl)-α-(ethoxycarbonyl)methylenetriphenylphosphorane
参考文献:
名称:
Cyclocondensation of alkylhydrazines and .beta.-substituted acetylenic esters: synthesis of 3-hydroxypyrazoles
摘要:
Addition of monosubstituted alkylhydrazines to acetylenic esters with either electron-withdrawing or sterically bulky beta-substituents afforded 1-alkyl-3-hydroxy-5-substituted-pyrazoles 1 as the major regioisomeric product. By comparison, the classical cyclocondensation of alkylhydrazines with beta-keto esters gives the regioisomeric pyrazol-5-ones 2. The reaction solvent employed in these cyclocondensations can have a profound effect on regioisomeric product ratios. Addition of methylhydrazine to 5g in methylene chloride gave regiospecific formation of pyrazolinone 2o, whereas addition in water-methanol mixtures afforded hydroxypyrazole 1o as the major product. Structural assignment of regioisomers 1 and 2 are based on C-13 NMR chemical shifts, long-range heteronuclear coupling constants, and comparisons with regiochemically known hydroxypyrazoles and/or pyrazolinones. Additions of acetylene 5b to 1,1-dimethylhydrazine afforded either acyclic enehydrazone 12 or pyrazolium betaine 13 depending on the reaction conditions.
Infrared spectroscopy and ab initio computation in conformer determination of keto ester and diketo triphenylphosphonium ylides
作者:Clifford A. Bunton、Fernando Castañeda
DOI:10.1016/j.molstruc.2009.07.028
日期:2009.11
fits for both keto ester and diketo ylides. For both methods agreement between observed and predicted frequencies is lowest for the syn – anti di- t -butyl keto ester ylide, although, unlike the situation for diester ylides, one bulky alkyl group does not significantly degrade the fits. Comparison of predicted and observed acyl stretching frequencies is useful in establishing conformations of these stabilized
A new series of disubstituted alkynes was obtained by microwave induced internal splitting of the corresponding beta-oxo-alkylidenetriphenylphosphoranes. The antimicrobial potential of these conjugated alkynes and phosphoranes was assayed in vitro against three Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, Staphylococcus epidermidis), three Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae) and five fungal strains (Aspergillus niger, Candida albicans, Aspergillus flavus, Candida rugosa, Saccharomyces cerevisiae). The 3-pyridylalkyne derivatives viz., 3-(6-chloropyridin-3-yl)propynenitrile (6a), 3-(2-chloropyridin-3-yl)propynenitrile (6b), ethyl 3-(6-chloropyridin-3-yl)propiolate (6c), iso-propyl 3-(6-chloropyridin-3-yl)propiolate (6d) and 3-(2,6-dichloro-5-fluoropyridin-3-yl) propynenitrile (6e) were found to be highly potent towards all tested microorganisms except E. coli. (C) 2013 Elsevier Masson SAS. All rights reserved.
Zinc promoted facile method for the acylation of ylides at α-carbon
Stabilised triphenylphosphonium ylides are acylated at the alpha-carbon with different acyl groups using zinc. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
Cyclocondensation of alkylhydrazines and .beta.-substituted acetylenic esters: synthesis of 3-hydroxypyrazoles
作者:Bruce C. Hamper、Mitchell L. Kurtzweil、James P. Beck
DOI:10.1021/jo00047a021
日期:1992.10
Addition of monosubstituted alkylhydrazines to acetylenic esters with either electron-withdrawing or sterically bulky beta-substituents afforded 1-alkyl-3-hydroxy-5-substituted-pyrazoles 1 as the major regioisomeric product. By comparison, the classical cyclocondensation of alkylhydrazines with beta-keto esters gives the regioisomeric pyrazol-5-ones 2. The reaction solvent employed in these cyclocondensations can have a profound effect on regioisomeric product ratios. Addition of methylhydrazine to 5g in methylene chloride gave regiospecific formation of pyrazolinone 2o, whereas addition in water-methanol mixtures afforded hydroxypyrazole 1o as the major product. Structural assignment of regioisomers 1 and 2 are based on C-13 NMR chemical shifts, long-range heteronuclear coupling constants, and comparisons with regiochemically known hydroxypyrazoles and/or pyrazolinones. Additions of acetylene 5b to 1,1-dimethylhydrazine afforded either acyclic enehydrazone 12 or pyrazolium betaine 13 depending on the reaction conditions.