Conversion of chiral unsaturated cyanohydrins into chiral carba- and heterocycles via ring-closing metathesis

Aliphatic unsaturated cyanohydrins served as starting materials in the synthesis of a set of new chiral unsaturated cyclic 1,2-ethanolamines. Combining a Grignard addition–NaBH4 reduction sequence with a ring-closing metathesis afforded unsaturated cyclic 1,2-ethanolamines and in good yields and high ee (96–99%). The conversion of cyanohydrins via a DIBAL reduction–transimination–NaBH4 reduction sequence, using allylamine, followed by ring-closing metathesis yielded tetrahydropyridines , tetrahydroazepinols and tetrahydroazocinols in high yields and excellent ee (97–99%).