NMR spectroscopy signals

Data obtained by ITC experiments were corroborated by saturation transfer difference (STD) NMR spectroscopy. Signals that arise during an STD experiment are a... 

The reaction of MP with 1-methyl- and l-phenyl-2-vinylpyrrole 20a,b afforded 1-substituted indole-4,7-dicarboxylie esters 27 via a further [4 + 2]-cycloaddition to the initially formed 6,7-dihydroindole-4-carboxylic ester 26 by a second molecule of MP, followed by a retro-Diels-Alder extrusion of ethene (80JOC4515). Maximum yields were obtained with 2 1 ratio of MP to vinylpyrrole. The intermediate adduct 26 could not be isolated and when the reaction was monitored by NMR spectroscopy, signals attributable to the dihydroindole-4-carboxylic ester 26 were of very low intensity, suggesting that the second and third steps of the reaction sequence were either comparable in rate or faster than the initial cycloaddition step. 

In NMR spectroscopy, signals of NMR-active nuclei with spin V2 (e.g., H, C, N, F, and P) have Lorentzian line shapes... 

The complexation is proved by NMR spectroscopy. Signals of the guests experience strong shifts (A6 = 1.5 ppm) to higher field the otherwise broad signals of the host are sharpened and shifted. The inclusion of guest compounds hinders the conformational flexibility of the host and adapts its shape to the enclosed molecule ( induced fit ). Small compounds like benzene or naphthalene are not complexed, neither are large compounds like coronene. Partially hydro-... 

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