A Robust, Recyclable Resin for Decagram Scale Resolution of (±)-Mefloquine and Other Chiral N-Heterocycles.

Decagram quantities of enantiopure (+)-mefloquine have been produced via kinetic resolution of racemic mefloquine using a ROMP-gel supported chiral acyl hydroxamic acid resolving agent. The requisite monomer was prepared in a few synthetic steps without chromatography and polymerization was safely performed on a >30 gram scale under ambient conditions. The reagent was readily regenerated and reused multiple times for the resolution of 150 grams of (±)-mefloquine and other chiral N-heterocylces.

Visible-Light-Driven Photoisomerization and Increased Rotation Speed of a Molecular Motor Acting as a Ligand in a Ruthenium(II) Complex.

Toward the development of visible-light-driven molecular rotary motors, an overcrowded alkene-based ligand and the corresponding ruthenium(II) complex is presented. In our design, a 4,5-diazafluorenyl coordination motif is directly integrated into the motor function. The photochemical and thermal isomerization behavior has been studied by UV/Vis and NMR spectroscopy. Upon coordination to a Ru(II) bipyridine complex, the photoisomerization process can be driven by visible (λmax = 450 nm) instead of UV light and furthermore, a large increase of the speed of rotation is noted. DFT calculations point to a contraction of the diazafluorenyl lower half upon metal-coordination resulting in reduced steric hindrance in the "fjord region" of the molecule. Consequently, it is shown that metal-ligand interactions can play an important role in the adjustment of both photophysical and thermodynamic properties of molecular motors.

Control of surface wettability using tripodal light-activated molecular motors.

Monolayers of fluorinated light-driven molecular motors were synthesized and immobilized on gold films in an altitudinal orientation via tripodal stators. In this design the functionalized molecular motors are not interfering and preserve their rotary function on gold. The wettability of the self-assembled monolayers can be modulated by UV irradiation.

Tetrapodal molecular switches and motors: synthesis and photochemistry.

The design, synthesis, and dynamic behavior of a series of novel tetrapodal molecular switches and motors containing common functional groups for attachment to various inorganic and organic surfaces are presented. Using a Diels-Alder reaction, an anthracene unit with four functionalized alkyl substituents ("legs") was coupled to maleimide-functionalized molecular switches or motors under ambient conditions. Terminal functional groups at the "legs" include thioacetates and azides, making these switches and motors ideal candidates for attachment to metallic or alkyne-functionalized surfaces. UV/vis absorption spectroscopy shows that the molecular switches and motors retain their ability to undergo reversible photoinduced and/or thermally induced structural changes after attachment to the tetrapodal anthracene.

Towards dynamic control of wettability by using functionalized altitudinal molecular motors on solid surfaces.

We report the synthesis of altitudinal molecular motors that contain functional groups in their rotor part. In an approach to achieve dynamic control over the properties of solid surfaces, a hydrophobic perfluorobutyl chain and a relatively hydrophilic cyano group were introduced to the rotor part of the motors. Molecular motors were attached to quartz surfaces by using interfacial 1,3-dipolar cycloadditions. To test the effect of the functional groups on the rotary motion, photochemical and thermal isomerization studies of the motors were performed both in solution and when attached to the surface. We found that the substituents have no significant effect on the thermal and photochemical processes, and the functionalized motors preserved their rotary function both in solution and on a quartz surface. Preliminary results on the influence of the functional groups on surface wettability are also described.

An integrated console for capsule-based, automated organic synthesis.

The current laboratory practices of organic synthesis are labor intensive, impose safety and environmental hazards, and hamper the implementation of artificial intelligence guided drug discovery. Using a combination of reagent design, hardware engineering, and a simple operating system we provide an instrument capable of executing complex organic reactions with prepacked capsules. The machine conducts coupling reactions and delivers the purified products with minimal user involvement. Two desirable reaction classes - the synthesis of saturated N-heterocycles and reductive amination - were implemented, along with multi-step sequences that provide drug-like organic molecules in a fully automated manner. We envision that this system will serve as a console for developers to provide synthetic methods as integrated, user-friendly packages for conducting organic synthesis in a safe and convenient fashion.

Observing second-order nonlinear optical properties by symmetry breaking in centrosymmetric furan-containing oligoaryl cyclophandienes.

Centrosymmetric furan-containing cyclophandienes 3 and 4, synthesized by our furan annulation protocol, have been shown to exhibit extraordinarily large Stokes shifts and second-order nonlinear optical beta values. The beta values for 3 and 4 measured at 1.32 mum are 208 and 530x10(-30) esu, respectively. The beta values of 3 and 4 are similar to those of respective cyclophenes 1 a and 7 in which strong hyperpoarizable interactions between two twisted pi-systems (oligoaryl and bridging double bond) might take place. Symmetry breaking due to the resonance contribution (cf. 2) and the unique structural features of 3 and 4 has been used to account for this unusual photophysical behavior.

Facile assembly of light-driven molecular motors onto a solid surface.

In order to improve the rotary motion of surface assembled light-driven molecular motors, tetra-acid-functionalized motors were bound to an amine-coated quartz surface without prior activation of the acid groups. In contrast to earlier bipodal motors, the tetravalent motor showed no significant reduction in the rotation speed when attached to a surface.