New bifunctional carbohydrate-like thiourea derivatives – design and first application in organocatalysis

From easily available aminopyran and aminooxepane derivatives and 2,5-bis(trifluoromethyl)phenyl isothiocyanate the corresponding thiourea derivatives were prepared. One compound was further modified by introducing a tertiary amino group. The four catalysts were then examined as catalysts in a Michael addition of acetylacetone to β-nitrostyrene. A 1:1 mixture of one of these thioureas with an (S)-prolinol derivative was also tested as catalyst, but no synergetic effect was found. The best yield achieved was 88% and the highest ee amounted to 39%. In a preliminary experiment, the aldol reaction of acetone with isatin was investigated. One catalyst provided the expected aldol product in low yield, but in excellent enantioselectivity.