Asymmetric Synthesis of <i>gem</i>-Difluoromethylenated Linear Triquinanes via Cascade <i>gem</i>-Difluoroalkyl Radical Cyclization

An asymmetric synthesis of <i>gem</i>-difluoromethylenated linear triquinanes is described exploiting the synthetic utilities of PhSCF₂TMS (<b>5</b>) as a “^•CF₂^–’’ building block. The strategy involves fluoride-catalyzed nucleophilic addition of PhSCF₂TMS (<b>5</b>) to chiral ketocyclopentenes <b>6</b> to provide silylated adducts <b>9</b> or alcohol derivatives <b>10</b> and <b>11</b>. Subsequent cascade radical cyclization of the <i>gem</i>-difluoroalkyl radical generated from silylated adducts <b>9</b> or alcohols <b>10</b> and <b>11</b> afforded <i>gem</i>-difluoromethylenated linear triquinanes <b>16</b> as an approximate 1:1 mixture of two diastereomers (<b>16A</b> and <b>16B</b>). Alternatively, a convenient asymmetric synthesis of <i>gem</i>-difluoromethylenated linear triquinanes <b>16A</b> can be accomplished by oxidation of <b>16a</b> (R = H) to provide ketotriquinane <b>17</b> followed by a highly stereoselective nucleophilic addition to <b>17</b> employing DIBAL, NaBH₄, and various Grignard reagents

A Series of Cyanoacetato Copper(II) Coordination Polymers with Various <i>N</i>,<i>N</i>′‑Ditopic Spacers: Structural Diversity, Supramolecular Robustness, and Magnetic Properties

Five novel copper­(II) coordination polymers containing cyanoacetate (cna) anion with various <i>N</i>,<i>N</i>′-ditopic spacers [Cu­(cna)₂­(pyz)]_<i>n</i> (<b>1</b>), [Cu­(cna)₂­(bpy)­(H₂O)₂]_<i>n</i> (<b>2</b>), [Cu­(cna)₂­(dpe)]_<i>n</i> (<b>3</b>), [Cu­(cna)₂­(dpe)]_<i>n</i>­(H₂O)_<i>n</i> (<b>4</b>), and [Cu­(cna)₂­(bpa)]_<i>n</i> (<b>5</b>) (when pyz = pyrazine, bpy = 4,4′-bipyridyl, dpe = 1,2-di­(4-pyridyl)­ethylene, and bpa = 1,2-di­(4-pyridyl)­ethane) were structurally and spectroscopically characterized. Compound <b>1</b> shows a two-dimensional (2D) sheet structure constructed from μ₂-1,3­(<i>syn,anti</i>) coordinative mode of cyanoacetate and μ₂-pyz linking adjacent Cu­(II) centers. Compound <b>2</b> exhibits a one-dimensional (1D) polymeric chain which is formed by μ₂-bpy bridging between [Cu­(cna)₂­(H₂O)₂] units, whereas compounds <b>3</b>–<b>5</b> reveal 1D ladder-like structures which are built from double-μ₂-dpe/bpa spacers connecting neighboring Cu­(II) cyanoacetate dimers. Weak interactions such as hydrogen bonding and N<i>···π</i> and/or C–H<i>···π</i> interactions join the adjacent layers of <b>1</b> or polymeric chains of <b>2</b>–<b>5</b> to stabilize overall supramolecular networks. The thermal stabilities of <b>1</b>–<b>5</b> were investigated. Interestingly, compound <b>2</b> reveals a robust supramolecular framework constructed by 1D polymeric chains during thermal dehydration and rehydration processes, which has been further verified by spectroscopic techniques, elemental analyses, thermogravimetric analysis, and X-ray powder diffraction. Moreover, this behavior is not observed in the isomorphous series containing Co­(II) and Ni­(II) ions. The magnetic properties of <b>1</b> and <b>3</b> exhibit very weak antiferromagnetic interactions between Cu­(II) centers

Asymmetric Synthesis of <i>gem</i>-Difluoromethylenated Linear Triquinanes via Cascade <i>gem</i>-Difluoroalkyl Radical Cyclization

An asymmetric synthesis of <i>gem</i>-difluoromethylenated linear triquinanes is described exploiting the synthetic utilities of PhSCF₂TMS (<b>5</b>) as a “^•CF₂^–’’ building block. The strategy involves fluoride-catalyzed nucleophilic addition of PhSCF₂TMS (<b>5</b>) to chiral ketocyclopentenes <b>6</b> to provide silylated adducts <b>9</b> or alcohol derivatives <b>10</b> and <b>11</b>. Subsequent cascade radical cyclization of the <i>gem</i>-difluoroalkyl radical generated from silylated adducts <b>9</b> or alcohols <b>10</b> and <b>11</b> afforded <i>gem</i>-difluoromethylenated linear triquinanes <b>16</b> as an approximate 1:1 mixture of two diastereomers (<b>16A</b> and <b>16B</b>). Alternatively, a convenient asymmetric synthesis of <i>gem</i>-difluoromethylenated linear triquinanes <b>16A</b> can be accomplished by oxidation of <b>16a</b> (R = H) to provide ketotriquinane <b>17</b> followed by a highly stereoselective nucleophilic addition to <b>17</b> employing DIBAL, NaBH₄, and various Grignard reagents

Synthesis of <i>gem</i>-Difluoromethylenated Polycyclic Cage Compounds

The synthesis of <i>gem</i>-difluoromethylenated polycyclic cage compounds, utilizing PhSCF₂SiMe₃ as a <i>gem</i>-difluoromethylene building block, is described. The fluoride-catalyzed nucleophilic addition of PhSCF₂SiMe₃ to both maleic anhydride–cyclopentadiene and maleic anhydride–cyclohexadiene adducts was accomplished with high stereoselectivity to provide the corresponding adducts that were treated with Grignard reagents, followed by acid-catalyzed lactonization to afford the corresponding γ-butyrolactones, each as a single isomer. These γ-butyrolactones underwent intramolecular radical cyclization to give the corresponding tetracyclic cage γ-butyrolactones, which were employed as precursors for the synthesis of <i>gem</i>-difluoromethylenated tetracyclic cage lactols or tetracyclic cage furans, upon treatment with Grignard reagents

Synthesis of <i>gem</i>-Difluoromethylenated Polycyclic Cage Compounds

The synthesis of <i>gem</i>-difluoromethylenated polycyclic cage compounds, utilizing PhSCF₂SiMe₃ as a <i>gem</i>-difluoromethylene building block, is described. The fluoride-catalyzed nucleophilic addition of PhSCF₂SiMe₃ to both maleic anhydride–cyclopentadiene and maleic anhydride–cyclohexadiene adducts was accomplished with high stereoselectivity to provide the corresponding adducts that were treated with Grignard reagents, followed by acid-catalyzed lactonization to afford the corresponding γ-butyrolactones, each as a single isomer. These γ-butyrolactones underwent intramolecular radical cyclization to give the corresponding tetracyclic cage γ-butyrolactones, which were employed as precursors for the synthesis of <i>gem</i>-difluoromethylenated tetracyclic cage lactols or tetracyclic cage furans, upon treatment with Grignard reagents