Keratoconus Diagnostic and Treatment Algorithms Based on Machine-Learning Methods.

The accurate diagnosis of keratoconus, especially in its early stages of development, allows one to utilise timely and proper treatment strategies for slowing the progression of the disease and provide visual rehabilitation. Various keratometry indices and classifications for quantifying the severity of keratoconus have been developed. Today, many of them involve the use of the latest methods of computer processing and data analysis. The main purpose of this work was to develop a machine-learning-based algorithm to precisely determine the stage of keratoconus, allowing optimal management of patients with this disease. A multicentre retrospective study was carried out to obtain a database of patients with keratoconus and to use machine-learning techniques such as principal component analysis and clustering. The created program allows for us to distinguish between a normal state; preclinical keratoconus; and stages 1, 2, 3 and 4 of the disease, with an accuracy in terms of the AUC of 0.95 to 1.00 based on keratotopographer readings, relative to the adapted Amsler-Krumeich algorithm. The predicted stage and additional diagnostic criteria were then used to create a standardised keratoconus management algorithm. We also developed a web-based interface for the algorithm, providing us the opportunity to use the software in a clinical environment.

Diverting Hydrogenations with Wilkinson's Catalyst towards Highly Reactive Rhodium(I) Species.

The addition of Barton's base has a dramatic effect on the classic rhodium(III)-mediated hydrogenations promoted by Wilkinson's catalyst. Following the initial oxidative addition, a barrierless reductive elimination of HCl from the traditional rhodium(III) intermediates instantly produces a rhodium(I) monohydride species, which is remarkably reactive in the hydrogenation of several internal alkynes and functionalized trisubstituted alkenes. The direct formation of this species is unprecedented upon addition of molecular hydrogen and its catalytic potential has been hitherto barely explored.

Chiral molecular tweezers: synthesis and reactivity in asymmetric hydrogenation.

We report the synthesis and reactivity of a chiral aminoborane displaying both rapid and reversible H2 activation. The catalyst shows exceptional reactivity in asymmetric hydrogenation of enamines and unhindered imines with stereoselectivities of up to 99% ee. DFT analysis of the reaction mechanism pointed to the importance of both repulsive steric and stabilizing intermolecular non-covalent forces in the stereodetermining hydride transfer step of the catalytic cycle.

Frustrated Lewis pair chemistry of chiral (+)-camphor-based aminoboranes.

Dimethylamino-(+)-camphorenamine reacted with an equimolar amount of Piers' borane, HB(C6F5)2, to give the corresponding iminium-hydroborate zwitterionic salt. Being in equilibrium with the parent enamine-HB(C6F5)2 N-B pair, this salt was able to split hydrogen heterolytically, hydrogenating the iminium group in the molecule. Detailed studies revealed that the hydrogen splitting in this reaction proceeded through an intermolecular pathway leading to a bornylamine-HB(C6F5)2 adduct. When the starting enamine is present in excess over HB(C6F5)2, the produced bornylamine-HB(C6F5)2 adduct breaks up, eliminating free bornylamine and forming the initial camphorenamine-HB(C6F5)2 pair. This results in hydrogenation of the camphorenamine framework in a catalytic fashion.

Synthesis and mesomorphic properties of calamitic malonates and cyanoacetates tethered to 4-cyanobiphenyls.

4-Cyano-1,1'-biphenyl derivatives bearing ω-hydroxyalkyl substituents were reacted with methyl 3-chloro-3-oxopropionate or cyanoacetic acid, giving liquid-crystalline linear malonates and cyanoacetates. These compounds formed monotropic nematic phases at 62 °C down to ambient temperature upon cooling from the isotropic liquid. The mesomorphic properties were investigated by differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction (WAXS).

Thermotropic Ionic Liquid Crystals.

The last five years' achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.

Structure and dynamic features of an intramolecular frustrated Lewis pair.

Di(mesityl)cyclohexenylphosphine undergoes hydroboration with Piers' borane [HB(C(6)F(5))(2)] to yield the cyclohexylene-anellated frustrated Lewis pair 5. This P/B pair splits H(2) with the formation of the product 4 and adds to the C=O double bond of phenyl isocyanate to yield 6. In the crystal, compound 5 features a puckered four-membered heterocyclic core structure with a long P-B bond (av. 2.197(5) Å). The activation energy of the P-B cleavage of the frustrated Lewis pair 5 was determined by dynamic (19)F NMR spectroscopy at ΔG(≠)(298 K)=12.1±0.3 kcal mol(-1).

Catalytic hydrogenation of sensitive organometallic compounds by antagonistic N/B Lewis pair catalyst systems.

The bis(arylimino-Cp)ZrCl2 complex (I) forms an "antagonistic" Lewis pair with B(C6F5)3. Treatment with dihydrogen yields the aminomethyl-Cp hydrogenation product (II) by means of a quasi-autocatalytic process. The salt III is an efficient catalyst for the hydrogenation of bulky imines and of silyl enolethers.