Selective palladium- and rhodium-catalyzed processes: I. Enantioselective synthesis of tetrahydroquinolines, II. The asymmetric hydroformylation reaction, III. Silystannylation-cyclization of diynes and alleneynes

Chapter 1. Sharpless asymmetric epoxidation (>90%e.e.) of a o-nitrocinnamyl alcohol led to an intermediate that was transformed into a 3-hydroxy-substituted tetrahydroquinoline. High-yielding Heck coupling of an o-nitroaryl iodide and α-acetamidoacrylate followed by a highly enantioselective rhodium-catalyzed asymmetric hydrogenation (>98%e.e.) gave a rapid and general entry into both R and S amino acids, which were further reacted to produce a 3-amino-substituted tetrahydroquinolines. Both the 3-hydroxy and 3-amino tetrahydroquinolines could serve as intermediates for the synthesis of biologically relevant cyclopropapyrroloindoles.; Chapter 2. The ability of DIOP derivatives to function as ligands in the rhodiumcatalyzed asymmetric hydroformylation reaction was investigated. Under mild reaction conditions (3–10 bars of H₂/CO gas pressure, 30–60°C), the hydroformylation of styrene, 2-vinylnaphthalene, vinyl acetate and N-vinylphthalimide using [1,4-disubstituted DIOP] ligands derived from D-mannitol led to improved regioselectivities ( e.g. linear to branched aldehyde ratio of 15:85 for the hydroformylation of styrene using (RSSR)-1,4-dimethyl-DIOP), compared to DIOP (e.g. linear to branched aldehyde ratio of 38:62 for the hydroformylation of styrene under the same reaction conditions). Steric (varying substituents at C₁ and C₄) or electronic (electron-withdrawing or donating groups on the phosphorous aryl rings) tuning of the modified DIOP ligands had little influence on the regioselection, possibly due to the lack of flexibility imposed by the isopropylidene ring which contains the C ₂-C₃ bond.; Chapter 3. The first example of a (Z,Z)- bis-alkylidenecyclohexane was synthesized by palladium-catalyzed silylstannylation-cyclization of a cis-4,5-O-isopropylidene-1,7-octadiyne-4,5-diol. The steric bulk of the silyl and stannyl substituents created an axial chirality in the structure, and the molecule exists as two diastereoisomers that do not display any fluxional behavior at temperatures below 60°C. This provided the first definitive example of a (Z,Z)-1,4-silylstannyldiene in which the atropisomerism has been frozen at or above room temperature. Silylstannylation of alleneynes derived from succinimide gave a rapid entry into highly functionalized indolizidines. While attempts synthesize bicyclic β-lactams by this route have not yet succeeded, preparation of several potentially useful allylstannane intermediates from β-lactam substrates highlighted the remarkable functional group compatibility of the silylstannylation reaction.