Ether, chloromethyl -menthyl

Another route to enantiomcrically pure iron-acyl complexes depends on a resolution of diastereomeric substituted iron-alkyl complexes16,17. Reaction of enantiomerically pure chloromethyl menthyl ether (6) with the anion of 5 provides the menthyloxymethyl complex 7. Photolysis of 7 in the presence of triphenylphosphane induces migratory insertion of carbon monoxide to provide a racemic mixture of the diastereomeric phosphane-substituted menthyloxymethyl complexes (-)-(/ )-8 and ( + )-( )-8 which are resolved by fractional crystallization. Treatment of either diastereomer (—)-(/J)-8 or ( I )-(.V)-8 with gaseous hydrogen chloride (see also Houben-Weyl, Vol 13/9a, p437) affords the enantiomeric chloromethyl complexes (-)-(R)-9 or (+ )-(S)-9 without epimerization of the iron center. 

A solution of 5 (from 44.2 g of the dimer) in 750 mL of THF is added under nitrogen by forced siphon through a stainless steel cannula to a stirred, cooled ( —78 X) solution of 50.9 g (0.54 mol) of chloromethyl menthyl ether (6) in 150 mL of THF. After addition, the solution is allowed to warm to 25 X, stirred for an additional 2 h. then the solvent is removed under reduced pressure. 800 mL of pentane are added and the slurry is filtered through a cake of anhyd MgS04. Solvent removal and chromatography of the residue [alumina, hexane, then (C2H5)20/hexane 1 10] affords menthyloxymethyl complex 7 as an amber oil yield 78.5 g (91%). 

Chiral pyridinium-based ionic liquids can be prepared by N-alkylation of pyridines with chloromethyl ()-menthyl ether <2006TA1728>. A room temperature ionic liquid brominating agent is obtained when A- -pcntylpyridinium bromide is reacted with bromine <2004SL1318>. 

Chiral recognition, enantioselectivity, and influence of room temperature CILs (RTIL) synthesized from 1-methyl imidazole and chloromethyl menthyl ether on excited-state photophysics of (5)-Ai-methyl-2-pyrrolidinemethyl 2(5)-(6-methoxy-2-naphthyl)propionate [(5,5)-NPX-PYR] was recently investigated using a fluorescence lifetime [114]. The chemical structures of the CILs and chiral analytes used for the lifetime study are shown in Fig. 21, left. The lifetime fluorescence decay of [(5,5)-NPX-PYR] in RTIL chiral environment is shown in Fig. 21, right. 

Fig. 21 Left Chemical structures of (7) (a) (-), and (b) (+)-RTIL synthesized from (-), and (+)-chloromethyl menthyl ether, respectively. (II) (a) (S,5)-NPX-PYR, (b) (S)-(+)-6-methoxy-2-naphthylpropionic acid [naproxen, NPX], (c) 1-hydroxy 2-naphthoic acid, and (d) 6-methoxy-2-naphthalene acetic acid. Right fluorescence decay traces (Lex = 266 nm,A,em > 300 nm) of (5,5)-NPX-PYR in (a) (-)- and (b) (+)-CILs. There is an 10% decrease in lifetime of (5,5)-NPX-PYR in (-l-)-CIL compared to that in (-)-CIL. The lifetime of (5,5)-NPX-PYR in acetonitrile is 3.1 ns in acetonitrile due to intramolecular electron transfer. In the CILs, the lifetime is significantly increased and there is a difference in lifetime in the two solvents. Adapted from [114]...

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