Asymmetric Synthesis Of 2-Methoxy-2-Methylchroman-7-Ol In Solid-State Beta-Cyclodextrin Complexes

A chiral product, (+)-2-methoxy-2-methylchroman-7-ol, was obtained from 8-cyclodextrin (8-CD)/1,3-dihydroxylbenzene (complex A) and methyl vinyl ketone/beta-cyclodextrin (complex B). The reaction was carried out at room temperature in a solid state to give the desired product in 82.8% yield and 78.4% ee. Low optically active product (19.5% ee) was obtained from complex B and 1,3-dihydroxylbenzene (A), and non-optically active product was obtained from complex A and methyl vinyl ketone (B) under the same conditions. The structures of the inclusion compounds were elucidated by melting points, X-ray diffraction, solid-state C-13 CP/MAS NMR (100 MHz, spin= 5000), and ROESY analyses. The ratios (1 : 1) of host-guest in the inclusion compounds were decided by H-1 NMR spectra (400 MHz). The mechanism of the solid-state conjugated cyclic addition reaction was also discussed.