New methods for preparation of tailor-made fluorine-containing compounds are in extremely high demand in nearly every sector of chemical industry. The asymmetric construction of quaternary C−F stereogenic centers is the most synthetically challenging and, consequently, the least developed area of research. As a reflection of this apparent methodological deficit, pharmaceutical drugs featuring C−F stereogenic centers constitute less than 1% of all fluorine-containing medicines currently on the market or in clinical development. Here we provide a comprehensive review of current research activity in this area, including such general directions as asymmetric electrophilic fluorination via organocatalytic and transition-metal catalyzed reactions, asymmetric elaboration of fluorine-containing substrates via alkylations, Mannich, Michael, and aldol additions, cross-coupling reactions, and biocatalytic approaches. CONTENTS

The use of computed interaction energies and distances as parameters in multivariate correlations is introduced for postulating noncovalent interactions. This new class of descriptors affords multivariate correlations for two diverse catalytic systems with unique noncovalent interactions at the heart of each process. The presented methodology is validated by directly connecting the noncovalent interactions defined through empirical dataset analyses to the computationally derived transition states.

Over the years, dirhodium(II) complexes have had an important role in the synthesis of numerous complex organic molecules because many useful transformations are mediated by this unique family of complexes. The recognized success of this class of catalysts relies on their bimetallic structure. They have a Rh−Rh bond, two axial ligands, and four bridging ligands responsible for controlling the catalyst electrophilicity and, in some cases, provide a mechanism for inducing asymmetry. The modification of the bridge ligand structure has been the main strategy to prepare new complexes, whereas the axial ligands have been considered to have a less important role in catalysis. This concept is changing, and over the past decade, the axial ligand modification was proven to be a valuable and simple strategy to prepare new complexes and achieve new reactivities. In this review a comprehensive overview of this topic is presented, with a particular focus on the changes induced by the axial coordination on the complex properties and reactivity.

Crystal clear: An integrated, simple, efficient, reusable, and scalable methodology for the dehydration of fructose to HMF offers outstanding yields and high purities. The method uses wet tetraethylammonium bromide as reaction medium, allowing the isolation of HMF by crystallization from the reaction medium. The process is also feasible starting from other carbohydrates, such as glucose, sucrose, or inulin.

In recent years, Stenhouse salts have attracted much attention as intermediates for the synthesis of cyclopenten-2-enones. This Minireview aims to present an overview of the methods for preparation, further transformation and applications of Stenhouse and Stenhouse-like salts. In this context, the Piancatelli rearrangement and its variants, and the recently reported donor-acceptor Stenhouse salts (DASA) will be addressed. The photophysical properties of DASA and its applications in colorimetric detection of amines, functionalization of polymers for detection of heat and nerve agents, photolithography and orthogonal photoswitching systems are discussed.

trans-4,5-Diamino-cyclopent-2-enones (CP) are usually prepared by Lewis acid-catalyzed condensation of furfural and a secondary amine in an organic solvent. The reaction proceeds through the formation of a Stenhouse salt (SS) intermediate followed by an electrocyclization reaction to afford the desired CP. Herein, we described the use of Cu(OTf) as a very efficient catalyst for the synthesis of CP in water at room temperature. Furthermore, the mild reaction conditions, catalyst reusability, and outstanding functional group tolerance suggest that this CP platform can be further used in chemical biology.

The development of a synthetic code that enables a sequence programmable feature like DNA represents a key aspect toward intelligent molecular systems. We developed herein the well-known dynamic covalent interaction between boronic acids (BAs) and catechols (CAs) into synthetic nucleobase analogs. Along a defined peptide backbone, BA or CA residues are arranged to enable sequence recognition to their complementary strand. Dynamic strand displacement and errors were elucidated thermodynamically to show that sequences are able to specifically select their partners. Unlike DNA, the pH dependency of BA/CA binding enables the dehybridization of complementary strands at pH 5.0. In addition, we demonstrate the sequence recognition at the macromolecular level by conjugating the cytochrome c protein to a complementary polyethylene glycol chain in a site-directed fashion.

Sweets for my sweet: The production and isolation of 5-hydroxymethylfurfural (HMF) in high yield and purity is demonstrated by using a combination of glucose-fructose isomerization with sweetzyme in wet tetraethylammonium bromide (TEAB) and clean fructose dehydration to HMF catalyzed by using HNO₃ under moderate conditions, which allow the reuse of any unreacted glucose and TEAB.