The controlled nitroxide-mediated homopolymerization of 9-(4-vinylbenzyl)-9H-carbazole (VBK) and the copolymerization of methyl methacrylate (MMA) with varying amounts of VBK were accomplished by using 10 mol % {tert-butyl[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino} nitroxide relative to 2-({tert-butyl[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]ami-no}oxy)-2-methylpropionic acid (BlocBuilder TM ) in dimethylformamide at temperatures from 80 to 125 C. As little as 1 mol % of VBK in the feed was required to obtain a controlled copolymerization of an MMA/VBK mixture, resulting in a linear increase in molecular weight versus conversion with a narrow molecular weight distribution (M w /M n % 1.3). Preferential incorporation of VBK into the copolymer was indicated by the MMA/VBK reactivity ratios determined: r VBK ¼ 2.7 6 1.5 and r MMA ¼ 0.24 6 0.14. The copolymers were found significantly ''living'' by performing subsequent chain extensions with a fresh batch of VBK and by 31 P NMR spectroscopy analysis. VBK was found to be an effective controlling comonomer for NMP of MMA, and such low levels of VBK comonomer ensured transparency in the final copolymer.

1,3-Dipolar cycloadditions of mesoionic 1,3-dipoles (Münchnones, imino-Münchnones, and phospha-Münchnones) with alkynes offer versatile, modular synthetic routes to pyrroles. Reactivity and regioselectivity differ markedly for different members of this series, and we report here the first general rationale for differences in reactivity by means of a systematic investigation of 1,3-dipolar cycloadditions involving electron-poor and electron-rich alkynes. Competition kinetic measurements indicate that Münchnones and phospha-Münchnones are nucleophilic 1,3-dipoles that react most rapidly with electron-poor alkynes. However, the regioselectivities of cycloadditions are found to undergo an inversion as a function of alkyne ionization potential. The exact point at which this occurs is different for the two dipoles, allowing rational control of the pyrrole formed. The origins of these reactivities and regioselectivities are examined computationally. Frontier molecular orbital predictions are found not to be accurate for these reactions, but transition state calculations give correct predictions of reactivity and selectivity, the origins of which can be analyzed using the distortion/interaction model of reactivity. Cycloadditions with electron-poor alkynes are shown to favor the regioisomer that has either the most favorable TS interaction energy (Münchnones or imino-Münchnones) or the smallest TS distortion energy (phospha-Münchnones). Cycloadditions with more electron-rich aryl-substituted alkynes, on the other hand, generally favor the regioisomer that has the smaller TS distortion energy. These insights delineate the synthetically important distinctions between Münchnones and phospha-Münchnones: phospha-Münchnones undergo highly regioselective cycloadditions with electron-poor alkynes that do not react selectively with Münchnones, and the reverse is true for cycloadditions of Münchnones with electron-rich alkynes.

A multicomponent strategy was applied to the synthesis of chiral bidentate unsaturated hydroxyalkyl- and carboxyalkyl-N-heterocyclic carbene (NHC) precursors. The newly developed low-cost chiral ligands derived from amino alcohols and amino acids were evaluated in copper-catalyzed asymmetric conjugated addition and asymmetric allylic alkylation, which afforded the desired tertiary and quaternary carbon stereocenters with excellent regio- and enantioselectivities (up to 99:1 e.r.).

CC coupling: DiPPAM 1 and BINAP 2 ligands led to divergent behaviors in the asymmetric conjugate addition (ACA) of dialkylzinc reagents to linear aryldienones, which were applied to the development of a highly selective sequential asymmetric 1,6/1,4-ACA process (see scheme; Tf = triflate, DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene).