Trinuclear Zirconium Polyhydride ({Cp*Zr(BH₃CH₃)}­(μ-H)₂­{Cp*Zr(BH₃CH₃)}­(μ-H)­{Cp*Zr(BH₃CH₃)})­(μ‑κ²_C,H:κ¹_C:κ²_C,H-CHBH₃) and Its Derivatives: Compounds Containing a Pentacoordinated Carbon Atom

The reaction of Cp*Zr­(BH₃CH₃)₃ with an excess amount of trimethylamine in a toluene solution yields the hypercarbon-containing complex ({Cp*Zr­(BH₃CH₃)}­(μ-H)₂­{Cp*Zr­(BH₃CH₃)}­(μ-H)­{Cp*Zr­(BH₃CH₃)})­(μ-κ²_C,H:κ¹_C:κ²_C,H-CHBH₃), <b>1</b>. To our knowledge, this is the first example in which a hypercoordinated carbon-containing complex was prepared from the reaction of a hydroborate complex with a Lewis base. The reaction of <b>1</b>, NaH, and [N­(CH₃)₄]Cl produces the anionic product [N­(CH₃)₄]­[({Cp*ZrCl}­{(μ-H)₂­{Cp*Zr­(BH₃CH₃)}}₂)­(μ-κ²_C,H:κ¹_C:κ²_C,H-CHBH₃)], <b>2</b>, whereas the reaction of <b>1</b> with B­(C₆F₅)₃ produces the hydride abstraction cationic product [({Cp*Zr­(BH₃CH₃)}­{(μ-H)­{Cp*Zr­(BH₃CH₃)}}₂)­(μ-κ²_C,H:κ¹_C:κ²_C,H-CHBH₃)]­[HB­(C₆F₅)₃], <b>3</b>. The further reaction of <b>3</b> with [N­(CH₃)₄]Cl and NaOH produces the neutral complex ({Cp*Zr­(BH₃CH₃)}­((μ-H)­{Cp*Zr­(BH₃CH₃)})₂)­(μ-κ²_C,H:κ¹_C:κ²_C,H-CHBH₃)­(μ₃-X) (X = Cl (<b>4</b>), OH (<b>5</b>)). Single-crystal X-ray structures of <b>1</b>, <b>2</b>, <b>3</b>, <b>4</b>, and <b>5</b> reveal a pentacoordinated carbon atom, which coordinates to a boron atom, a hydrogen atom, and three Zr atoms in each complex. The geometry around the hypercarbon in each complex can be best described as either distorted trigonal bipyramidal or distorted square pyramidal. The μ₃-bridging Cl^– ligand in <b>4</b> and OH^– ligand in <b>5</b> bond to three Zr atoms on the opposite side of the hypercarbon. These hypercarbon-containing complexes were further characterized by elemental analysis, infrared spectroscopy, and NMR spectroscopy. Formations of <b>2</b>–<b>5</b> confirm the robust framework of the hypercarbon when undergoing reactions

Organocatalytic Enantioselective Michael–Michael–Michael–Aldol Condensation Reactions: Control of Five Stereocenters in a Quadruple-Cascade Asymmetric Synthesis of Highly Functionalized Hexa­hydro­phenan­threnes

A cascade organocatalysis has been developed for the enantioselective synthesis of a highly functionalized hexahydrophenanthrene-2-carbaldehyde containing five contiguous stereogenic centers with high diastereoselectivity and high enantioselectivity (>99% <i>ee</i>). The one-pot method comprises a cascade of organocatalytic Michael–Michael–Michael–aldol reactions of 2-methyl-1,5-dinitro-3-((<i>E</i>)-2-nitrovinyl)­benzene and α,β-unsaturated aldehydes (e.g., cinnamaldehyde). The structure and absolute configuration of a product were confirmed by X-ray analysis of an appropriate derivative

Trinuclear Zirconium Polyhydride ({Cp*Zr(BH₃CH₃)}­(μ-H)₂­{Cp*Zr(BH₃CH₃)}­(μ-H)­{Cp*Zr(BH₃CH₃)})­(μ‑κ²_C,H:κ¹_C:κ²_C,H-CHBH₃) and Its Derivatives: Compounds Containing a Pentacoordinated Carbon Atom

The reaction of Cp*Zr­(BH₃CH₃)₃ with an excess amount of trimethylamine in a toluene solution yields the hypercarbon-containing complex ({Cp*Zr­(BH₃CH₃)}­(μ-H)₂­{Cp*Zr­(BH₃CH₃)}­(μ-H)­{Cp*Zr­(BH₃CH₃)})­(μ-κ²_C,H:κ¹_C:κ²_C,H-CHBH₃), <b>1</b>. To our knowledge, this is the first example in which a hypercoordinated carbon-containing complex was prepared from the reaction of a hydroborate complex with a Lewis base. The reaction of <b>1</b>, NaH, and [N­(CH₃)₄]Cl produces the anionic product [N­(CH₃)₄]­[({Cp*ZrCl}­{(μ-H)₂­{Cp*Zr­(BH₃CH₃)}}₂)­(μ-κ²_C,H:κ¹_C:κ²_C,H-CHBH₃)], <b>2</b>, whereas the reaction of <b>1</b> with B­(C₆F₅)₃ produces the hydride abstraction cationic product [({Cp*Zr­(BH₃CH₃)}­{(μ-H)­{Cp*Zr­(BH₃CH₃)}}₂)­(μ-κ²_C,H:κ¹_C:κ²_C,H-CHBH₃)]­[HB­(C₆F₅)₃], <b>3</b>. The further reaction of <b>3</b> with [N­(CH₃)₄]Cl and NaOH produces the neutral complex ({Cp*Zr­(BH₃CH₃)}­((μ-H)­{Cp*Zr­(BH₃CH₃)})₂)­(μ-κ²_C,H:κ¹_C:κ²_C,H-CHBH₃)­(μ₃-X) (X = Cl (<b>4</b>), OH (<b>5</b>)). Single-crystal X-ray structures of <b>1</b>, <b>2</b>, <b>3</b>, <b>4</b>, and <b>5</b> reveal a pentacoordinated carbon atom, which coordinates to a boron atom, a hydrogen atom, and three Zr atoms in each complex. The geometry around the hypercarbon in each complex can be best described as either distorted trigonal bipyramidal or distorted square pyramidal. The μ₃-bridging Cl^– ligand in <b>4</b> and OH^– ligand in <b>5</b> bond to three Zr atoms on the opposite side of the hypercarbon. These hypercarbon-containing complexes were further characterized by elemental analysis, infrared spectroscopy, and NMR spectroscopy. Formations of <b>2</b>–<b>5</b> confirm the robust framework of the hypercarbon when undergoing reactions

Organocatalytic Enantioselective Michael–Michael–Michael–Aldol Condensation Reactions: Control of Six Stereocenters in a Quadruple-Cascade Asymmetric Synthesis of Polysubstituted Spirocyclic Oxindoles

An organocatalyzed enantioselective Michael–Michael–Michael–aldol cascade reaction for the construction of cyclopentane fused spirooxindoles was achieved. The domino reaction provided the spirooxindoles with six contiguous stereocenters including a quaternary center in good yields (55–64%) with excellent enantioselectivities (up to >99% <i>ee</i>). Enantioselective Michael–Michael–Michael–aldol condensation–aromatization reactions of an isomeric product were observed

Self Assembly of Silver(I) Complexes Containing 1,4-Bis[(3-pyridyl)ethynyl]benzene

One-dimensional (1-D) zigzag chains of {[Ag<b>L</b>]­(ClO₄)­·0.5Et₂O}<i>_n</i> (<b>1</b>), {[Ag<b>L</b>]­(OTf)·Et₂O}_<i>n</i> (<b>2</b>), and {[Ag<b>L</b>]­(BF₄)­·0.5CH₃OH}_<i>n</i> (<b>3</b>) were obtained from the reaction of AgClO₄, AgCF₃SO₃, and AgBF₄ with 1,4-bis­(pyridine-3-ylethynyl)­benzene (<b>L</b>), respectively, in similar reaction conditions, whereas it led to the formation of a 1-D sinusoidal chain of {[Ag<b>L</b>(NO₃)]·H₂O}_<i>n</i> (<b>4</b>) and a metallolocycle of [Ag₂<b>L</b>₆]­(BF₄)₂ (<b>5</b>) in a different reaction procedure for the AgNO₃ and AgBF₄ cases. Complexes <b>1</b>–<b>3</b> form 1-D zigzag chains, and every two chains are further stacked to give a pair of chains assisted by weak Ag­(I)···Ag­(I) and π···π interactions, whereas a single 1-D sinusoidal chain of <b>4</b> can only be obtained. Although the reaction is carried out in a similar reaction as <b>4</b> except that BF₄^– was used instead of NO₃^–, a metallocycle of <b>5</b> was obtained instead. It is noted that only the bridging <b>L</b> ligands in <b>5</b> adopt a syn conformation, whereas those in <b>1</b>–<b>4</b> are in an anti conformation. In this regard, this work has demonstrated the delicate effects of anions and reaction conditions on the assembly reactions of complexes <b>1</b>–<b>5</b>. In addition, we observed a structural transformation during the heating process for <b>5</b>. Although the powder X-ray diffraction pattern of <b>5</b> at 210 °C is similar to that of <b>3</b>, it cannot be conclusively proven by powder X-ray diffraction studies at this moment due to the presence of some mismatches between both patterns of <b>5</b> and <b>3</b>

One-Pot Asymmetric Synthesis of Seven-Membered Carbocycles Cyclohepta[<i>b</i>]indoles via a Sequential Organocatalytic Michael/Double Friedel–Crafts Alkylation Reaction

A new method has been developed for the enantioselective synthesis of highly functionalized cyclohepta[<i>b</i>]indoles with high enantioselectivity (up to 96% <i>ee</i>). The process combines an enantioselective organocatalytic Michael addition and a highly efficient double Friedel–Crafts reaction sequence in one pot with good yields and stereoselectivity. The structures and absolute configurations of the products were confirmed by X-ray analysis

Self Assembly of Silver(I) Complexes Containing 1,4-Bis[(3-pyridyl)ethynyl]benzene

One-dimensional (1-D) zigzag chains of {[Ag<b>L</b>]­(ClO₄)­·0.5Et₂O}<i>_n</i> (<b>1</b>), {[Ag<b>L</b>]­(OTf)·Et₂O}_<i>n</i> (<b>2</b>), and {[Ag<b>L</b>]­(BF₄)­·0.5CH₃OH}_<i>n</i> (<b>3</b>) were obtained from the reaction of AgClO₄, AgCF₃SO₃, and AgBF₄ with 1,4-bis­(pyridine-3-ylethynyl)­benzene (<b>L</b>), respectively, in similar reaction conditions, whereas it led to the formation of a 1-D sinusoidal chain of {[Ag<b>L</b>(NO₃)]·H₂O}_<i>n</i> (<b>4</b>) and a metallolocycle of [Ag₂<b>L</b>₆]­(BF₄)₂ (<b>5</b>) in a different reaction procedure for the AgNO₃ and AgBF₄ cases. Complexes <b>1</b>–<b>3</b> form 1-D zigzag chains, and every two chains are further stacked to give a pair of chains assisted by weak Ag­(I)···Ag­(I) and π···π interactions, whereas a single 1-D sinusoidal chain of <b>4</b> can only be obtained. Although the reaction is carried out in a similar reaction as <b>4</b> except that BF₄^– was used instead of NO₃^–, a metallocycle of <b>5</b> was obtained instead. It is noted that only the bridging <b>L</b> ligands in <b>5</b> adopt a syn conformation, whereas those in <b>1</b>–<b>4</b> are in an anti conformation. In this regard, this work has demonstrated the delicate effects of anions and reaction conditions on the assembly reactions of complexes <b>1</b>–<b>5</b>. In addition, we observed a structural transformation during the heating process for <b>5</b>. Although the powder X-ray diffraction pattern of <b>5</b> at 210 °C is similar to that of <b>3</b>, it cannot be conclusively proven by powder X-ray diffraction studies at this moment due to the presence of some mismatches between both patterns of <b>5</b> and <b>3</b>

One-Pot Asymmetric Synthesis of Seven-Membered Carbocycles Cyclohepta[<i>b</i>]indoles via a Sequential Organocatalytic Michael/Double Friedel–Crafts Alkylation Reaction

A new method has been developed for the enantioselective synthesis of highly functionalized cyclohepta[<i>b</i>]indoles with high enantioselectivity (up to 96% <i>ee</i>). The process combines an enantioselective organocatalytic Michael addition and a highly efficient double Friedel–Crafts reaction sequence in one pot with good yields and stereoselectivity. The structures and absolute configurations of the products were confirmed by X-ray analysis

One-Pot Asymmetric Synthesis of Seven-Membered Carbocycles Cyclohepta[<i>b</i>]indoles via a Sequential Organocatalytic Michael/Double Friedel–Crafts Alkylation Reaction

A new method has been developed for the enantioselective synthesis of highly functionalized cyclohepta[<i>b</i>]indoles with high enantioselectivity (up to 96% <i>ee</i>). The process combines an enantioselective organocatalytic Michael addition and a highly efficient double Friedel–Crafts reaction sequence in one pot with good yields and stereoselectivity. The structures and absolute configurations of the products were confirmed by X-ray analysis

Organocatalytic Enantioselective Michael–Michael–Henry Reaction Cascade. An Entry to Highly Functionalized Hajos–Parrish-Type Ketones with Five to Six Contiguous Stereogenic Centers and Two Quaternary Carbons

An organocatalytic enantioselective reaction of 2-methylcyclopentane-1,3-dione, nitroalkene, and α,β-unsaturated aldehyde with the diphenylprolinol catalyst was developed to give the highly functionalized Hajos–Parrish-type ketones with five to six contiguous stereocenters and two quaternary carbon stereogenic centers with high diastereoselectivity and enantioselectivity. The structures of the adducts were unambiguously confirmed by single-crystal X-ray crystallographic analyses of the appropriate products