Organocatalytic asymmetric ring opening reactions of epoxide

In paralel with fascinating developments of asymmetric organocatalysts in recent years, design and synthesis of new organocatalysts, finding new application fields or improving available results are one of the most important targets of the researchers. It is important to prepare organocatalysts on of the essential requirement in development of these kinds of catalysts is to avoid the number of competing diastereomeric processes. This can be achieved by designing molecules with C2-symmetry.This work involves the synthesis of chiral catalysts derived from amino alcohols and their effect on asymmetric ring opening of glycidol with phenol, p-methoxyphenol and p-methylphenol as nucleophiles. The synthesis of some of catalysts (1-6) we previously reported.7 and 8 with C2-simetry were synthesized from the reactions of (S)-phenylethyl amine, (S)-1,2-propane diol and (S)-3-(phenoxy)-1,2-propane diol with 46 % and 49 % yields respectively. The synthesis of compunds 9 and 10 were achieved by dibenzylation of (R,R)-1,2-diaminocyclohexane followed by reacted with (S)-propyleneoxide and (R)-glycidol with 99 % and 33 % yields respectively. Non-symmetrical amino alcohols 10-13 were synthesized by the reactions of (R)-N-benzyl-cyclohexylethyl amine with (S)-glycidol, racemic phenyl glycidil ether and (R)-styreneoxide in high yields. Compund 14 were synthesized by the reaction of (R)-cyclohexylethyl amine with two eqivalent amount of (R)-styrene oxide in 69 % yield.Chiral amino alcohols were used as organocatalysts in the asymmetric ring opening of racemic glycidol with phenol, p-methoxyphenol and p-methylphenol as nucleophiles. Enantioselectivity was determined by HPLC using Chiralcell-OD column. Calayst 8 showed best selectivity with phenol (ee 96 %) and (ee 77 %) for p-methoxyphenol while catalyst 3 and 13 produced a selectivity of 97 % ee and % 64 ee with phenol.