Imidazolidine Diels-Alder reaction

Park, J., Sreekanth, P., and Kim, B. (2004) Recycling chiral imidazolidin-4-one catalyst for asymmetric Diels-Alder reactions ... 

MPEG with chiral imidazolidin-4-one =5,000" =0.2" CH3CN/H2O" En an tios elective Diels-Alder reactions Precipitation (diethyl ether) (r) [139]... 

Others. Pyridazine can undergo Diels-Alder reactions with inverse electron demand. An example has been reported between pyridazine and 2-methylene-imidazolidine. The Diels-Alder product loses nitrogen gas readily followed by ring aromatiza-tion to afford iVdV -dimethyl-JV-phenyl-l,2-ethanediainine in 84% yield (eq 15). 

For an example of an a-selenenylation of enolizable aldehydes in the presence of polystyrene-supported imidazolidin-4-ones see Reference [22]. Dixon and coworkers described an aryloxylation process of aldehydes using an inverse electron demand hetero-Diels-Alder reaction of in situ generated enamines and o-quinone [23]. Enantioenriched a-oxygenated products were isolated with good yields. 

The influence of solvents [64] and comparisons with catalysts of the diarylpro-linol series [65] were reported. For theoretical calculations on stereocontrol see Reference [66]. In addition, imidazolidin-4-one catalyzed cycloadditions have been used in several total syntheses of natural products. Intramolecular Diels-Alder reactions (IMDA) were reported as key steps in the synthesis of bicyclo-undecenes [67], amaminols [68], solanapyrones [69], telomerase inhibitor UCS1025A [70], englerin A [71], (-)-nor-platencin [72], and muironolide A [73]. In addition, asymmetric [3-1-2]-cycloadditions of azomethines were accomphshed in the presence of chiral imidazoUdinones [74]. Intermolecular cycloadditions of dihydropyridine 53 and acrolein catalyzed by imidazolidin-4-ones were reported. The chiral azabicyclo-octenol 54 was isolated as the important key intermediate in the total synthesis of lycopodium alkaloids [75] (e.g., ludduline) and oseltamivir (Scheme 4.19) [76]. 

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