Separation of Lutidine Isomers by Selective Enclathration

The host compound 3,3′-bis(9-hydroxy-9-fluorenyl)-2-2′-binaphthyl, H1, has been employed to separate the six isomers of lutidine. Competition experiments showed that the preference for enclathration is in the sequence 3,4-LUT > 2,6-LUT > 2,3-LUT > 2,5-LUT > 2,4-LUT ≈ 3,5-LUT. The structures yielded results that agree with the ¹H NMR analyses and with the thermal analysis. The effects of mixed hosts and vapor-phase competitions were briefly explored with two extra hosts, namely, 2,2′-bis(1-hydroxy-4,5-dihydro-2:3,6:7-dibenzocycloheptadien-1-yl)biphenyl (H2) or 3,3′-bis(di-p-tolylhydroxymethyl)-1,1′-binaphthyl (H3).