Corey ± Bakshi ± Shibata (CBS) reduction of the 1,1'-diacylmetallocenes 5 and 7 provides the C 2 -symmetrical diols 4 and 10, which proved to be useful starting materials for stereocontrolled ligand synthesis. Diols 4 and 10 can be easily converted to a wide range of diamines, diphosphines, and dithioacetates by nucleophilic substitution of the hydroxyl function with full retention of configuration. Furthermore, the aminophosphines 30 and 31 become easily accessible. Compounds 30 and 31 have been used as ligands in enantioselective cross-coupling of racemic secondary Grignard reagents with vinyl bromides. A selectivity up to 93 % ee could be reached for the first time in the preparation of (S)-(E)-1,3-diphenyl-1-butene (34 b), which was transformed into the enantiomerically pure chiral building block 37 with a pseudoasymmetric center in a straightforward, threestep synthesis.

The hydroboration of olefins with Et(2)BH provides diethyl(alkyl)boranes 2 which readily undergo a boron-zinc exchange with Et(2)Zn providing a range of polyfunctional primary, secondary, and benzylic diorganozincs. The resulting diorganozincs 3 have been reacted with various electrophiles (allylic halides, acid chlorides, alkylidenemalonates, ethyl propiolate, nitroolefins) in the presence of CuCN.2LiCl with excellent yields. With secondary dialkylzincs prepared from diastereomerically pure diethyl(alkyl)boranes, the boron-zinc exchange occurs with loss of stereochemistry. The asymmetric addition of 3 to aldehydes in the presence of the chiral catalyst 55 furnishes optically active polyfunctional secondary alcohols (50 to over 96% ee).

The first total syntheses of (+/-)-didehydrostemofoline (1) and (+/-)-isodidehydrostemofoline (3) are reported. The synthesis begins with the Diels-Alder reaction of readily available pyrrole 9 and ethyl (E)-3-nitroacrylate, the latter serving as a regioinverted equivalent of ketene. After hydrogenation to prevent retro-Diels-Alder reaction, the major cycloadduct is transformed to 7-azabicyclo[2.2.1]heptanol 14. Aza-Cope-Mannich reaction of the formaldiminium derivative of 14 delivers 1-azatricyclo[5.3.0.04.10]decane 15, which in 15 additional steps is converted to 1 and 3.

Enantioselective total syntheses of aloperine (1), N-methylaloperine (2), and N-allylaloperine (3) are reported. The central element of the synthetic strategy is an intramolecular Diels−Alder reaction in which the cycloaddends are tethered by a N-silylamine linkage. The total synthesis of 1 proceeds from commercially available 3-hydroxypiperidine hydrochloride (54) and (R)-pipecolinic acid (35) by way of nine isolated and purified intermediates. The synthesis is sufficiently efficient that gram quantities of (+)-aloperine (1) can be readily prepared. Early exploratory studies also introduced a convenient method for tethering cycloaddition partners with a sulfonamide unit to realize the intramolecular Diels−Alder cycloaddition of a vinylsulfonamide:  45 → 46.

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