Water and organic synthesis: a focus on the in-water and on-water border. Reversal of the in-water Breslow hydrophobic enhancement of the normal endo-effect on crossing to on-water conditions for Huisgen cycloadditions with increasingly insoluble organic liquid and solid 2π-dipolarophiles.
J Org Chem
; 78(7): 3276-91, 2013 Apr 05.
Article
in En
| MEDLINE
| ID: mdl-23463988
ABSTRACT
Measurements of the endo/exo product ratios for Huisgen cycloadditions with a series of vinyl ketones, alkyl acrylates, and substituted styrenes as dipolarophiles with phthalazinium and pyridazinium dicyanomethanide 1,3-dipoles in acetonitrile and water show that as the reactions change from in-water (large hydrophobic enhancement of endo-products) to on-water, the hydrophobic enhancement of the endo-products is reduced and partially reversed (relative to acetonitrile). An expected increase of the endo-effect with increasing hydrophobic character of the dipolarophile is overcome by decreasing water solubility causing changeover to on-water conditions. On-water reactions do not show increased cycloaddition endo-effects (relative to organic solvents) as do in-water reactions.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
J Org Chem
Year:
2013
Document type:
Article
Affiliation country:
Ireland