Cellulose and cellulose derivatives are biopolymers which are often used as stationary phases for the separation of enantiomers. Describing the mechanism of such separations is a difficult task due to the complexity of these phases. In the present study, we attempt to elucidate the types of interactions occurring between a diol intermediate for a LTD(4) antagonist and a tris(4-methylbenzoate)-derivatized cellulose stationary phase. Thermodynamic studies indicate that, at low temperatures, the enantioselectivity is entropy driven. At higher temperatures, the separation is enthalpy driven. DSC and IR experiments reveal that the transitions between the enthalpic and the entropic regions of the van't Hoff plots are a result of a change in conformation of the stationary phase. Investigation of chromatographic kinetic parameters reveals that, at low temperature, the second eluted enantiomer undergoes sluggish inclusion interactions. Subtle changes in the structure of the analyte indicates that π-π interactions do not contribute to enantioselectivity. Finally, molecular modeling of (R)- and (S)-diol and the stationary phase suggests that hydrogen bonding is a primary factor in the separation, and the calculated energy values obtained from the molecular modeling correlate well with the chromatographic elution order.

The Suzuki±Miyaura cross-coupling reaction using heterogeneous Pd/C has a homogeneous component. The soluble palladium concentration increases during the reaction reaching a maximum at ca. 90% conversion before falling to < 4 ppm.

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The development of a short and efficient synthesis of a complex 6-azaindole, BMS-663068, is described. Construction of the 6-azaindole core is quickly accomplished starting from a simple pyrrole, via a regioselective Friedel-Crafts acylation, Pictet-Spengler cyclization, and a radical-mediated aromatization. The synthesis leverages an unusual heterocyclic N-oxide α-bromination to functionalize a critical C-H bond, enabling a highly regioselective copper-mediated Ullmann-Goldberg-Buchwald coupling to install a challenging triazole substituent. This strategy resulted in an efficient 11 step linear synthesis of this complex clinical candidate.

This first paper on the topic of polydimethylsiloxane–vinyl block polymers describes the development of a unique class of vinyl functional silicon containing free–radical initiators which can be used in the synthesis of block polymers. Details of the synthesis and characterization of these initiators are described together with the kinetics of their thermolysis. Specific conditions are described under which these initiators can be condensed with α,ω‐hydrogen functional polydimethylsiloxane oligomers by a platinum‐catalyzed hydrosilylation reaction to yield macroinitiators.