The design and synthesis of three organic nonlinear optical crystals is presented for terahertz (THz) generation that incorporates the optimal characteristics of known organic nonlinear optical crystals 4‐(4‐(dimethylamino)styryl)‐1‐methylpyridinium 4‐methylbenzenesulfonate (DAST) and 2‐(4‐hydroxy‐3‐methoxystyryl)‐1‐methylquinolinium 2,4,6‐trimethylbenzenesulfonate (HMQ‐TMS). The three crystals feature the 4‐((4‐(dimethylamino)phenyl)ethynyl)‐1‐methylpyridin‐1‐ium (4DEP) cation and three different anion combinations. Gas phase ab initio calculations of the cation show that 4DEP has a larger hyperpolarizability than cations from both DAST and HMQ‐TMS. To obtain the molecular packing needed for large nonlinear optical susceptibility and efficient THz generation, three anions are tested that result in noncentrosymmetric crystals: 4‐methylbenzenesulfonate, 3‐nitrobenzenesulfonate, and napthalene‐2‐sulfonate. After synthesis and crystallization, the crystal structure is characterized via X‐ray diffraction (XRD) analysis, and the relative THz generation efficiency for ideal crystals is predicted. 4DEP‐N2S shows a roughly 30% larger relative second‐order nonlinear optical susceptibility compared to HMQ‐TMS and DAST and, therefore, shows promise as a new advanced THz generation crystal.

Cross couplings between simple allylic alcohols and aryl and vinyl boronic acids are efficiently catalyzed by nickel(0) catalysts and bidentate N-heterocyclic carbene/phosphine ligands. The bidentate nature of the ligand is shown to extend catalyst lifetime and enable high yields of the corresponding cross-coupling products. X-ray crystallography confirms the bidentate nature of the ligand scaffold. Multistep cross coupling-alkene/alkyne insertions reactions are also conducted and the bidentate nature of the substrate makes the pendant phosphine of the ligand unnecessary.

We report the synthesis of bimetallic Pd­(I) and Pd­(II) complexes with bidentate 2-phosphinoimidazole ligands and their catalytic activity to generate substituted naphthalenes. This process involves the coupling of an aryl iodide and 2 equiv of a ketone via sequential ketone α-arylation and then annulation to generate disubstituted and tetrasubstituted naphthalenes in a regioselective manner. Excellent substrate scope for both aryl iodide and ketone partners is demonstrated, including that for heteroaryl iodides. Bimetallic Pd complexes are much more reactive than monometallic Pd catalysts in this transformation. Density functional theory calculations, isotope effect experiments, and substrate competition experiments were used to examine bimetallic mechanisms, reactivity, and selectivity.

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Site-selective modification of bioactive natural products is an effective approach to generating new leads for drug discovery. Herein, we show that heterogeneous nanoparticle catalysts enable site-selective monoreduction of polyazide substrates for the generation of aminoglycoside antibiotic derivatives. The nanoparticle catalysts are highly chemoselective for reduction of alkyl and aryl azides under mild conditions and in the presence of a variety of easily reduced functional groups. High regioselectivity for monoazide reduction is shown to favor reduction of the least sterically hindered azide. We hypothesize that the observed selectivity is derived from the greater ability of less-hindered azide groups to interact with the surface of the nanoparticle catalyst. These results are complementary to previous Staudinger reduction methods that report a preference for selective reduction of electronically activated azides.

We have developed a solvent-dependent method for the synthesis of novel benzo-δ-sultone scaffolds. A variety of benzylbenzo[e][1,2]oxathiin-4(3H)-one-2,2-dioxides were obtained in high yields in DMF using a one-pot, DBU-catalyzed condensation of 2-hydroxybenzaldehydes with a number of (E)-2-phenylethenesulfonyl chlorides. On the other hand, the initially prepared 2-formylphenyl-(E)-2-phenylethenesulfonate derivatives underwent DBU-catalyzed reactions to a series of 3-[methoxy(phenyl)methyl]benzo[e][1,2]oxathiine-2,2-dioxides in moderate to good yields in MeOH. These reactions presumably proceed via DBU-catalyzed O-sulfonylation/intramolecular Baylis-Hillman/1,3-H shift or dehydration tandem sequences, respectively.