Kinetic Resolution of Tertiary Propargylic Alcohols by Enantioselective Cu−H‐Catalyzed Si−O Coupling

A broad range of tertiary propargylic alcohols were kinetically resolved by catalyst‐controlled enantioselective silylation. This non‐enzymatic kinetic resolution is catalyzed by a Cu?H species and makes use of the commercially available precatalyst MesCu/(R,R)‐Ph‐BPE and a simple hydrosilane as the resolving reagent. Both alkyl,aryl‐ as well as dialkyl‐substituted propargylic alcohols participate, and especially high selectivity factors are achieved when the alkyne terminus carries a TIPS group, which also enables facile post‐functionalization in this position (s up to 207).     

Enantioselective Catalysts for the Synthesis of α‐Substituted Allylboronates—An Accelerated Approach towards Isomerically Pure Homoallylic Alcohols

The use of a convenient protecting group for boronates allows a selective, catalyzed S_N2′ reaction to generate allylboronates which are applied for the synthesis of enantiomerically pure homoallylic alcohols. Depending on the configuration of both catalyst and the protecting group any of the four possible stereoisomers can be formed. The rationale behind the selective addition is supported by density functional theory calculations.     

Enantioselective Formation of All‐Carbon Quaternary Stereocenters from Indoles and Tertiary Alcohols Bearing A Directing Group

Described is an efficient catalytic asymmetric intermolecular C? C bond‐formation process to generate acyclic all‐carbon quaternary stereocenters. The reactions overcome the unfavorable steric hindrance around reactive centers, and the competitive elimination (E1), to form a range of useful indole products with excellent efficiency and enantioselectivity.     

How to Make a DNA Chip

Microarrays are one of the hottest areas in biological research today. Microarrays have been mostly applied to nucleic acid analysis, specifically to the assessment of which genes are being expressed and at what level. Early microarrays were prepared by using photolithographic methods, which were more commonly used for integrated circuit (“computer chip”) production. Hence the colloquial term “DNA chip” came into being. The completion of the sequencing of the human genome and that of many other organisms makes the determination of gene function an important next step in understanding the role of DNA in the processes of life. DNA microarrays are an excellent tool to address this question because their numerous probe sites enable the analysis of many genes simultaneously. With good experience in this initial use, many further applications of microarrays are being developed, including genotyping in research and genetic diagnosis in medicine. DNA microarrays have made abundantly clear the power of vast parallelism in biological analysis, which is raising interest in other types of microarrays (small‐molecule, protein). Many applications for DNA microarrays have been developed and clearly many more will emerge through the creativity of the scientists who use them. In early studies, users produced their own microarrays. The apparent power of microarrays has demanded improvements in production methods, and technologies from physical sciences and engineering are now being applied to DNA chips. Many branches of chemistry can contribute to improved methods: from synthetic chemistry (to attach or prepare DNA), to the physical chemistry of surfaces, to analytical chemistry (to assess surface reactions).     

Tertiary α‐Silyl Alcohols by Diastereoselective Coupling of 1,3‐Dienes and Acylsilanes Initiated by Enantioselective Copper‐Catalyzed Borylation

An efficient synthesis of functionalized tertiary α‐silyl alcohols by an enantio‐ and diastereoselective copper‐catalyzed three‐component coupling of 1,3‐dienes, bis(pinacolato)diboron, and acylsilanes is reported. The reaction proceeds well with different 1,3‐dienes and a broad range of aryl‐ as well as alkenyl‐ but also alkyl‐substituted acylsilanes. The target compounds are formed with high regio‐, diastereo‐, and enantioselectivity (up to 99 % ee and d.r. >20:1) and are highly versatile synthetic building blocks.     

Enzymatic Approach to and Odor Description of the Twelve Enantiomerically Pure Isomers of Pelargene®

Pelargene^® is a commercial fragrance sold as a mixture of three regioisomeric pyran derivatives ( 1 – 3 ). The enantiomers of each of the two possible diastereoisomers of 1 – 3 were prepared by means of a biocatalyzed approach, and the odor properties of the twelve isolated stereoisomers were evaluated.     

How to prepare a chiral Grignard reagent: a theoretical proposal

It is shown that two competitive pathways (T2 vs T4) exist for Grignard reagent formation. While the nonradical pathway T2 leads to retention of the configuration, the radical pathway T4 gives racemization. Our calculations suggest the way that T2 can be enhanced, which should be of significance to prompt new synthesis approaches for the preparation of chiral Grignard reagents.     

Copper‐Catalyzed Regio‐ and Enantioselective Addition of Silicon Grignard Reagents to Alkenes Activated by Azaaryl Groups

A new application of silicon Grignard reagents in C(sp³)?Si bond formation is reported. With the aid of BF₃?OEt₂, these silicon nucleophiles add across alkenes activated by various azaaryl groups under copper catalysis. An enantioselective version employing benzoxazole‐activated alkenes as substrates and a CuI‐josiphos complex as catalyst has been developed, forming the C(sp3)?Si bond with good to high enantiomeric ratios (up to 97:3). The method expands the toolbox for “conjugate addition” type C(sp³)?Si bond formation.