Generation of Axially Chiral Fluoroallenes through a Copper-Catalyzed Enantioselective ß-Fluoride Elimination.

Herein we report the copper-catalyzed silylation of propargylic difluorides to generate axially chiral, tetrasubstituted monofluoroallenes in both good yields (27 examples >80%) and enantioselectivities (82-98% ee). Compared to previously reported synthetic routes to axially chiral allenes (ACAs) from prochiral substrates, a mechanistically distinct reaction has been developed: the enantiodiscrimination between enantiotopic fluorides to set an axial stereocenter. DFT calculations and vibrational circular dichroism (VCD) suggest that ß-fluoride elimination from an alkenyl copper intermediate likely proceeds through a syn-ß-fluoride elimination pathway rather than an anti-elimination pathway. The effects of the C1-symmetric Josiphos-derived ligand on reactivity and enantioselectivity were investigated. Not only does this report showcase that alkenyl copper species (like their alkyl counterparts) can undergo ß-fluoride elimination, but this elimination can be achieved in an enantioselective fashion.

Gold-Catalyzed Hydrofluorination of Electron-Deficient Alkynes: Stereoselective Synthesis of ß-Fluoro Michael Acceptors.

The gold(I)-catalyzed, stereoselective hydrofluorination of electron-deficient alkynes with triethylamine trihydrogen fluoride (Et3N·3HF) is described. Fluorinated α,ß-unsaturated aldehydes, amides, esters, ketones, and nitriles were isolated in moderate to good yields as single diastereomers. In all but four cases, the (Z)-vinyl fluorides were initially formed in ≥97% diastereoselectivity. This work constitutes the first catalytic example of the diastereoselective preparation of a variety of ß-alkyl, ß-fluoro Michael acceptors from alkynes. Additionally, the described work expands access to ß-aryl, ß-fluoro Michael acceptors to the synthesis of ß-fluoro-α,ß-unsaturated amides and nitriles. The monofluoroalkenes formed through this strategy were readily transformed into other fluorine-containing compounds, and the developed method was applied to the synthesis of a fluorinated analogue of Exoderil, a topical antimycotic.

Homologation of α-aryl amino acids through quinone-catalyzed decarboxylation/Mukaiyama-Mannich addition.

A new method for amino acid homologation by way of formal C-C bond functionalization is reported. This method utilizes a 2-step/1-pot protocol to convert α-amino acids to their corresponding N-protected ß-amino esters through quinone-catalyzed oxidative decarboxylation/in situ Mukaiyama-Mannich addition. The scope and limitations of this chemistry are presented. This methodology provides an alternative to the classical Arndt-Eistert homologation for accessing ß-amino acid derivatives. The resulting N-protected amine products can be easily deprotected to afford the corresponding free amines.

Crystal structures of 4-chloro-pyridine-2-carbo-nitrile and 6-chloro-pyridine-2-carbo-nitrile exhibit different inter-molecular π-stacking, C-H⋯Nnitrile and C-H⋯Npyridine inter-actions.

The two title compounds are isomers of C6H3ClN2 containing a pyridine ring, a nitrile group, and a chloro substituent. The mol-ecules of each compound pack together in the solid state with offset face-to-face π-stacking, and inter-molecular C-H⋯Nnitrile and C-H⋯Npyridine inter-actions. 4-Chloro-pyridine-2-carbo-nitrile, (I), exhibits pairwise centrosymmetric head-to-head C-H⋯Nnitrile and C-H⋯Npyridine inter-actions, forming one-dimensional chains, which are π-stacked in an offset face-to-face fashion. The inter-molecular packing of the isomeric 6-chloro-pyridine-2-carbo-nitrile, (II), which differs only in the position of the chloro substituent on the pyridine ring, exhibits head-to-tail C-H⋯Nnitrile and C-H⋯Npyridine inter-actions, forming two-dimensional sheets which are π-stacked in an offset face-to-face fashion. In contrast to (I), the offset face-to-face π-stacking in (II) is formed between mol-ecules with alternating orientations of the chloro and nitrile substituents.

Kinetic and physiological analysis of the GAME(Wheels) system.

For individuals with a spinal cord injury or dysfunction (SCI/D), opportunities to exercise are limited and are usually not highly motivating experiences. Exercise programs or extracurricular activities may help increase or maintain the cardiovascular fitness level of individuals with SCI/D. The GAME(Wheels) system, an interface between a portable roller system and a computer, enables an individual to control a video game by propelling his or her wheelchair. The purpose of this study was to investigate whether the propulsive forces used during video play, both with and without the GAME(Wheels) system, were different. A secondary purpose was to examine differences in metabolic parameters during exercise under these two conditions. Ten manual wheelchair users exercised on the GAME(Wheels) system with and without controlling a video game. Physiological and kinetic data were collected six times during two exercise trials. Kinetic data were recorded with the SMART(Wheel) and used to investigate propulsion forces. No significant differences were found in the resultant force, rate of rise, or number of hand contacts with the pushrims. This study showed that propulsion pattern did not change significantly when wheelchair users exercised while playing a computer video game. Oxygen consumption, ventilation, and heart rate were significantly different (p < 0.05) between the two groups during the last three exercise intervals and cooldown. Playing a video game while exercising may help to motivate manual wheelchair users to exercise longer and regularly, something that was reported by this study's subjects; likewise, exercising while playing a video game may not be associated with higher pushrim forces and stroke frequencies.