(S)-2-[bis-(3,5-bistrifluoromethylphenyl)trimethylsilyloxymethyl]pyrrolidinium perchlorate in water T=4°C; Diels-Alder reaction; 36 h; Inert atmosphere; optical yield given as percent eeenantioselective reaction;

(5R)-(+)-2,2,3-trimethyl-5-benzyl-4-imidazolidinone monohydrochloride T=23°C; Diels-Alder cycloaddition; Title compound not separated from byproducts;