Although gem -diborylalkenes are known to be among the most valuable reagents in modern organic synthesis, providing a rapid access to a wide array of transformations, including the construction of C–C and C-heteroatom bonds, their use as dienophile-reactive groups has been rare. Herein we report the Diels–Alder (DA) reaction of (unsymmetrical) gem -diborylalkenes. These reactions provide a general and efficient method for the stereoselective conversion of gem -diborylalkenes to rapidly access 1,1-bisborylcyclohexenes. Using the same DA reaction manifold with borylated-dienes and gem- diborylalkenes, we also developed a concise, highly regioselective synthesis of 1,1,2-tris- and 1,1,3,4-tetrakis(boronates)cyclohexenes, a family of compounds that currently lack efficient synthetic access. Furthermore, DFT calculations provided insight into the underlying factors that control the chemo-, regio-, and stereoselectivity of these DA reactions. This method also provides stereodivergent syntheses of gem- diborylnorbornenes. The utility of the gem- diborylnorbornene building blocks was demonstrated by ring-opening metathesis polymerization (ROMP), providing a highly modular approach to the first synthesis of the gem- diboron-based polymers. Additionally, these polymers have been successfully submitted to postpolymerization modification reactions. Given its simplicity and versatility, we believe that this novel DA and ROMP approach holds great promise for organoboron synthesis as well as organoboron-based polymers and that it will result in more novel transformations in both academic and industrial research.
Although gem-diborylalkenes are known to be among the most valuable reagents in modern organic synthesis, providing a rapid access to a wide array of transformations, including the construction of C−C and C‐heteroatom bonds, their use as dienophile-reactive groups has been rare. Herein we report the Diels-Alder (DA) reaction of (unsymmetrical) gem-diborylalkenes. These reactions provide a general and efficient method for the stereoselective conversion of gem-diborylalkenes to rapidly access 1,1-bisborylcyclohexenes. Using the same DA reaction manifold with borylated-dienes and gem-diborylalkenes, we also developed a concise, highly regioselective synthesis of 1,1,2-tris- and 1,1,3,4-tetrakis(boronates)cyclohexenes, a family of compounds that currently lack efficient synthetic access. Furthermore, DFT calculations provided insight into the underlying factors that control the chemo-, regio, and stereoselectivity of these DA reactions. This method also provides stereodivergent syntheses of gem-diboryl-norbornenes. The utility of the gem-diboryl-norbornene building blocks was demonstrated by ring-opening metathesis polymerization (ROMP), providing a highly modular approach to the first synthesis of the gem-diboron-based polymers. Given its simplicity and versatility, we believe that this novel DA and ROMP approach holds great promise for organoboron synthesis as well as organoboron-based polymers and that it will result in more novel transformations in both academic and industrial research.<br>
We report a designed stereodivergent strategy for the synthesis of gem‐diborylcyclopropanes. The reaction provides a highly modular approach to prepare cyclopropane ring variants bearing gem‐(Bpin,Bpin), gem‐(Bpin,Bdan), and gem‐(Bpin,BF3K), with outstanding levels of stereocontrol. This was achieved by diastereoselective Pd‐catalyzed cyclopropanation reactions of gem‐diborylalkenes with α‐diazoarylacetates and α‐diazoaryl‐trifluoromethyl. The key to the success of this general protocol was the diastereoselective trifluorination reaction of gem‐diborylcyclopropanes, followed by the stereospecific interconversion of the trifluoroborate salts into the Bdan group.
Many inorganic materials can form crystals, but little is known about their enantioselective crystallization. Herein, we report on the enantioselective crystallization of ϵ‐Zn(OH)2 (Wulfingite) chiral crystals by using amino acids. Crystals of ϵ‐Zn(OH)2 were crystallized from supersaturated sodium hydroxide and zinc nitrate aqueous solutions in the presence of l‐ or d‐arginine. All of the chiral measurements, such as selective chiral adsorption by circular dichroism (CD), chiral chromatography, and polarimetry measurements, clearly show chiral discrimination during the crystallization of ϵ‐Zn(OH)2. In addition, a new method has been developed for identifying chirality in crystals by using electron paramagnetic resonance (EPR). Although the values of chiral induction of the ϵ‐Zn(OH)2 crystals obtained are somewhat low, these values are still significant because they demonstrate that enantioselectivity during the crystallization of chiral inorganic crystals with chiral additives can be achieved. The method can be applied to many chiral inorganic systems. Understanding and controlling the crystallization of chiral inorganic crystals is important for gaining knowledge on the interaction of chiral molecules with inorganic surfaces. This knowledge can lead to an understanding of basic scientific questions such as the evolution of homochirality in biomolecules and the development of chiral inorganic crystals for a variety of purposes such as asymmetric catalysis and optical applications.
The first practical, fully stereoselective P(V)-radical hydrophosphorylation is presented herein by using simple, limonene-derived reagent systems. A set of reagents have been developed that upon radical initiation react smoothly with olefins and other radical acceptors to generate P-chiral products, which can be further diversified (with conventional 2e– chemistry) to a range of underexplored bioisosteric building blocks. The reactions have a wide scope with excellent chemoselectivity, and the unexpected stereochemical outcome has been supported computationally and experimentally. Initial ADME studies are suggestive of the promising properties of this rarely explored chemical space.
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