Isopinocampheylborane Derivatives with >99% ee via the DMAP Complex

The complex 8 of isopinocampheylborane and p-(dimethylamino)pyridine (DMAP) can be obtained with >99% ee starting from α-pinene with 80−90% ee by hydroboration using DMAP·BH3 (5) activated by 5% iodine, or by the conventional hydroboration of α-pinene, followed by addition of DMAP. Purification of the air-stable 8 is readily accomplished by crystallization from methanol. Conversion of 8 into the trifluoroborate adduct 1 using KHF2 occurs without erosion of ee. Generation of the derived 2 in situ with TMSCl as the fluorophile also occurs with little, if any, loss of ee, as evidenced by the preparation of the salicaldimine complex 11 and the derived amino alcohol 12 with 94% ee overall.