Escaping from Flatland: Stereoconvergent Synthesis of Three-Dimensional Scaffolds via Ruthenium(II)-Catalyzed Noyori–Ikariya Transfer Hydrogenation

Noyori–Ikariya-type ruthenium(II)-catalysts for asymmetric transfer hydrogenation (ATH) have been known for 25 years and have proved as a well-behaved and user-friendly platform for the synthesis of chiral secondary alcohols. A progress has been made in the past five years in understanding the asymmetric reduction of complex ketones, where up to four stereocenters can be controlled in a single chemical transformation. Intriguing multi-chiral molecular architectures are therefore available in few well understood and robust synthetic steps from commercially available building blocks and possess handles for additional functionalization. The aim of this Review is to showcase the availability of three-dimensional scaffolds and homochiral lead-like compounds via ATH and inspire their direct use in drug discovery endeavors. Basic mechanistic insights are provided to demystify the stereo-chemical outcomes, as well as examples of diastereoselective transformations of enantiopure alcohols to give a feeling of how these rigid non-planar molecules can be further elaborated.     

Necessary and sufficient nonnegativity conditions for second-order coordinate trigonometric splines

Necessary and sufficient nonnegativity conditions for continuous differentiable coordinate trigonometric splines of the second order are obtained; the convexity and concavity intervals of these splines are determined. The method of investigation consists in recognizing concavity in intervals adjacent to the endpoints of the support of a coordinate spline under consideration and applying arguments related to the number of zeros of the solution of the corresponding boundary value problem for a second-order differential equation.     

Solution of the problems of spacecraft aerothermodynamics

The review presents the materials concerning investigation of aerogasdynamics and thermal protection of missiles during their launch and flight and of re-entering spacecraft accomplished from the foundation of NII-88 (now TsNIIMash) to Gagarin’s flight. The experimental and theoretico-computational studies, chiefly not reported in accessible publications, are outlined.     

[2+2+2] Cycloisomerisation of Aromatic Cyanodiynes in the Synthesis of Pyridohelicenes and Their Analogues

We have developed a methodology for the synthesis of pyridohelicenes and their analogues based on the Ni⁰‐, Co^I‐ or Rh^I‐mediated intramolecular [2+2+2] cycloisomerisation of cyanodiynes. It allows for folding the linear precursors into the corresponding helical backbones comprising the newly formed pyridine unit in their central part. Along with racemic pyrido[n]helicenes (n=5,6,7) and their derivatives, both enantio‐ and diastereomerically pure pyrido[n]helicene‐like molecules (n=5,6) were prepared by employing the chiral substrate‐controlled cyclisation of the corresponding enantiopure cyanodiynes.     

Dihydroquinazolinones via A3-Type Reactions of N-Carbamoyliminium Ions

A variant of the A³ coupling reaction was developed utilizing in situ generated N-carbamoyliminium ions. The tandem INCIC/A³-coupling sequence provided a facile one-pot synthesis of dihydroquinazolinone derivatives. The scope of the reaction was demonstrated in solution as well as on solid support. The reaction was further combined with peptide synthesis, S_NAr reactions, CuAAC triazole formation or bromination, providing additional opportunities for further diversification of the dihydroquinazolinone scaffolds.