TFA-catalyzed trimerization of R-(+)-6-methyl-tetrahydro-pyran-2-one

The enantiomerically pure (≥98% ee) title compound R-(+)-6-methyl-tetrahydro-pyran-2-one (R)-1 in the presence of traces of trifluoroacetic acid (TFA) converts into an equilibrium mixture with its trimer 4 [(R)-1:4=20:80] corresponding to a ΔG≅−0.8 kcal mol−1. The transformation can be followed by 1H and 13C NMR spectroscopy. The structure of 4 was established by chemical correlation with (R)-1 and its molecular weight determined via its colligative properties.