Ferroelectric liquid crystals. 6. Synthesis of nonracemic aryl cyanohydrin ethers

In connection with our project directed toward the design and synthesis of high-performance ferroelectric liquid crystals, we have developed a generally applicable synthetic route to chiral nonracemic aryl cyanohydrin ethers. The synthesis is illustrated herein by preparation of the arylbenzoate 1 (R{sub 1} = n-decyl, R{sub 2} = n-pentyl), which results in a straightforward manner from benzoylation of the key phenol intermediate 7. Phenol 7 derives from Mitsunobu coupling of p-(benzyloxy)phenol (3) with nonracemic N-({alpha}-hydroxyacyl)oxazolidone 2 prepared by the method of Evans. It is shown that this coupling proceeds predominantly with inversion of configuration. Conversion of the resulting N-({alpha}-(aryloxy)acyl)oxazolidone 4 to amide 5 by treatment with dimethylaluminum amide, dehydration to nitrile 6 by the action of trimethylsilyl polyphosphoric acid, and then debenzylation promoted by trimethylsilyl iodide gives 7 in 51% overall yield from 2.