Laxmidhar Rout

CUO NANOPARTICLES CATALYZED C-N, C-O, AND C-S CROSS-COUPLING REACTIONS: SCOPE AND MECHANISM

CuO nanoparticles have been studied for C-N, C-O, and C-S bond formations via cross-coupling reactions of nitrogen, oxygen, and sulfur nucleophiles with aryl halides. Amides, amines, imidazoles, phenols, alcohols and thiols undergo reactions with aryl iodides in the presence of a base such as KOH, Cs(2)CO(3), and K(2)CO(3) at moderate temperature. The procedure is simple, general, ligand-free, and efficient to afford the cross-coupled products in high yield.

Isothermal calorimetric titrations on charge-assisted halogen bonds: role of entropy, counterions, solvent, and temperature.

We have conducted isothermal calorimetric titrations to investigate the halogen-bond strength of cationic bidentate halogen-bond donors toward halides, using bis(iodoimidazolium) compounds as probes. These data are intended to aid the rational design of halogen-bond donors as well as the development of halogen-bond-based applications in solution. In all cases examined, the entropic contribution to the overall free energy of binding was found to be very important. The binding affinities showed little dependency on the weakly coordinating counteranions of the halogen-bond donors but became slightly stronger with higher temperatures. We also found a marked influence of different solvents on the interaction strength. The highest binding constant detected in this study was 3.3 × 10(6) M(-1).

Allene Carboxylates as Dipolarophiles in Rh‐Catalyzed Carbonyl Ylide Cycloadditions

have recently begun a program aimed at utilizing the unique structural features of axially chiral allenes to predictably control the stereochemical outcome of cycloaddition reactions as the key step in the synthesis of various natural products. We are particularly interested in cycloaddition reactions for which catalyst control of stereochemistry would be difficult, either from a mechanistic standpoint or due to substrate instability. Upon scanning the literature we were surprised to find a dearth of examples in which the axial chirality of allenes was employed to control the stereochemical outcome of dipolar cycloadditions (e.g. 1!3). There were also rather limited examples of allenes being used in carbonyl ylide cycloadditions. Herein we report that carboxylate-functionalized allenes can serve as dipolarophiles for carbonyl ylides and that excellent levels of allene facial selectivity can be achieved. Our first task was to determine the feasibility of using electron-deficient allenes as dipolarophiles. To test this we examined the Rh-catalyzed cycloaddition between diazocarbonyl compound 1 a and the achiral allene 2 a (Table 1). Attempting the reaction in CH2Cl2 or 1,2-dichloroethane (DCE) did not result in product formation, even at elevated temperatures (Table 1, entries 1–3). However, running the reaction in refluxing toluene formed 3 and 4 in a 2.5:1 diastereomeric ratio (Table 1, entry 4). Gratifyingly, the two diastereomers could be separated and their identity was determined by the magnitude of the allylic coupling constants. Running the reaction in benzene resulted in a slightly diminished yield with no dramatic improvement on

Synthesis, structure, and application of self-assembled copper(II) aqua complex by H-bonding for acceleration of the nitroaldol reaction on water.

Simple addition: Copper(II) aqua complex 1 can be prepared in a one-pot synthesis and is self-assembled by H-bond interactions. Complex 1 is shown to accelerate the nitroaldol reaction on water, which is a heterogeneous process, requiring no additive or base, and 1 can be recycled without loss of activity. Copper(II) aqua complex 1 has been prepared in a one-pot synthesis. The single crystal X-ray analysis showed that the complex is self-assembled through aqua ligands by H-bond interactions and the copper(II) atoms are pentacoordinated with square pyramidal geometry. Complex 1 has been studied for the acceleration of the nitroalodol reaction on water. It is a clean technological process and the catalyst can be recycled without loss of activity.

Synthesis, Structure and Application of Chiral Copper(II) Coordination Polymers for Asymmetric Acylation

Chiral copper(II) coordination polymers 1a-c have been prepared by one-pot synthesis in high yield. Their single-crystal X-ray analysis showed that repeating units are connected to each other by carboxylate linker and copper(II) atoms are pentacoordinated with distorted square-pyramidal geometry for 1a-b and square-planar geometry for 1c. These polymers have catalyzed the kinetic resolution of secondary alcohols by acylation with up to 90% ee ( s = 50).