Correction to One-Pot Synthesis of Asymmetric Annulated Bis(pyrrole)s

Correction to One-Pot Synthesis of Asymmetric Annulated Bis(pyrrole)

Access to Substituted Dihydrothiopyrano[2,3‑<i>b</i>]indoles via Sequential Rearrangements During <i>S</i>‑Alkylation and Au-Catalyzed Hydroarylation on Indoline-2-thiones

An efficient methodology for the synthesis of indole-fused dihydrothiopyrans has been developed from indoline-2-thiones. The protocol involves the synthesis of conjugated ene-yne-substituted indole-sulfides, a gold­(III)-catalyzed rearrangement of the ene-yne side chain followed by intramolecular hydroarylation via C3–H functionalization of the indole core. This new synthesis of functionalized tricyclic indole derivatives through sequential rearrangements is quite general in natur

Au-Catalyzed Synthesis of Thiopyrano­[2,3‑<i>b</i>]­indoles Featuring Tandem Rearrangement and Hydroarylation

Gold­(III)-catalyzed synthesis of 14-π electron heteroaromatic thiopyrano­[2,3-<i>b</i>]­indole is reported using conjugated enyne tethered indole sulfides, featuring skeletal rearrangement conjoined with intramolecular hydroarylation (via C3–H functionalization of the indole core) and oxidative aromatization. Subsequent Pd-catalyzed C–C coupling resulted in a 16-π electron heteroaromatic isothio­chromeno­[1,8,7-<i>bcd</i>]­indole

Synthesis, Characterization, and Properties of Weakly Coordinating Anions Based on <i>tris</i>-Perfluoro-<i>tert</i>-Butoxyborane

A convenient method for the preparation of strongly Lewis acidic <i>tris</i>-perfluoro-<i>tert</i>-butoxyborane B­(OR^F)₃ (<b>1</b>), (OR^F = OC­(CF₃)₃) was developed, and its X-ray structure was determined. <b>1</b> was used as a precursor, guided by density functional theory (DFT) calculations and volume-based thermodynamics, for the synthesis of [NEt₄]­[NCB­(OR^F)₃] (<b>3</b>) and [NMe₄]­[FB­(OR^F)₃] (<b>5</b>) and the novel large and weakly coordinating anion salts [Li 15-Crown-5]­[B­(OR^F)₄] (<b>2</b>) and [NEt₄]­[CN­{B­(OR^F)₃}₂] (<b>4</b>). The stability of [B­(OR^F)₄]⁻ was compared with that of some related known weakly coordinating anions by appropriate DFT calculations

Synthesis, Characterization, and Properties of Weakly Coordinating Anions Based on <i>tris</i>-Perfluoro-<i>tert</i>-Butoxyborane

A convenient method for the preparation of strongly Lewis acidic <i>tris</i>-perfluoro-<i>tert</i>-butoxyborane B­(OR^F)₃ (<b>1</b>), (OR^F = OC­(CF₃)₃) was developed, and its X-ray structure was determined. <b>1</b> was used as a precursor, guided by density functional theory (DFT) calculations and volume-based thermodynamics, for the synthesis of [NEt₄]­[NCB­(OR^F)₃] (<b>3</b>) and [NMe₄]­[FB­(OR^F)₃] (<b>5</b>) and the novel large and weakly coordinating anion salts [Li 15-Crown-5]­[B­(OR^F)₄] (<b>2</b>) and [NEt₄]­[CN­{B­(OR^F)₃}₂] (<b>4</b>). The stability of [B­(OR^F)₄]⁻ was compared with that of some related known weakly coordinating anions by appropriate DFT calculations

Synthesis, Characterization, and Properties of Weakly Coordinating Anions Based on <i>tris</i>-Perfluoro-<i>tert</i>-Butoxyborane

A convenient method for the preparation of strongly Lewis acidic <i>tris</i>-perfluoro-<i>tert</i>-butoxyborane B­(OR^F)₃ (<b>1</b>), (OR^F = OC­(CF₃)₃) was developed, and its X-ray structure was determined. <b>1</b> was used as a precursor, guided by density functional theory (DFT) calculations and volume-based thermodynamics, for the synthesis of [NEt₄]­[NCB­(OR^F)₃] (<b>3</b>) and [NMe₄]­[FB­(OR^F)₃] (<b>5</b>) and the novel large and weakly coordinating anion salts [Li 15-Crown-5]­[B­(OR^F)₄] (<b>2</b>) and [NEt₄]­[CN­{B­(OR^F)₃}₂] (<b>4</b>). The stability of [B­(OR^F)₄]⁻ was compared with that of some related known weakly coordinating anions by appropriate DFT calculations

Reactions of a Cyclodimethylsiloxane (Me₂SiO)₆ with Silver Salts of Weakly Coordinating Anions; Crystal Structures of [Ag(Me₂SiO)₆][Al] ([Al] = [FAl{OC(CF₃)₃}₃], [Al{OC(CF₃)₃}₄]) and Their Comparison with [Ag(18-Crown-6)]₂[SbF₆]₂

Two silver-cyclodimethylsiloxane cation salts [AgD₆]­[Al] ([Al] = [Al­(OR_F)₄]­(<b>1</b>) or [FAl­(OR_F)₃]­(<b>2</b>), R_F = C­(CF₃)₃, D = Me₂SiO) were prepared by the reactions of Ag­[Al] with D₆ in SO₂(l). For a comparison the [Ag­(18-crown-6)]₂[SbF₆]₂(<b>3</b>) salt was prepared by the reaction of Ag­[SbF₆] and 18-crown-6 in SO₂(l). The compounds were characterized by IR, multinuclear NMR, and single crystal X-ray crystallography. The structures of <b>1</b> and <b>2</b> show that D₆ acts as a pseudo crown ether toward Ag⁺. The stabilities and bonding of [MD_<i>n</i>]⁺ and [M­(18-crown-6)]⁺ (M = Ag, Li, <i>n</i> = 4–8) complexes were studied with theoretical calculations. The calculations predicted that D₆ adopts a puckered <i>C</i>_<i>i</i> symmetric structure in the gas phase in contrast to previous reports. 18-Crown-6 was calculated to bind more strongly to Li⁺ and Ag⁺ than D₆. ²⁹Si­[¹H] NMR results in solution, and calculations in the gas phase established that a hard Lewis acid Li⁺ binds more strongly to D₆ than Ag⁺. A comparison of the [MD_<i>n</i>]⁺ complex stabilities showed D₇ to form the most stable metal complexes in the gas phase and the solid state and explained why [AgD₇]­[SbF₆] was isolated in a previous reaction where ring transformations resulted in an equilibrium of [AgD_<i>n</i>]⁺ complexes. In contrast, the isolations of <b>1</b> and <b>2</b> were possible because the corresponding equilibrium of [AgD_<i>n</i>]⁺ complexes was not observed with [Al]⁻ anions. The formation of the dinuclear complex salt <b>3</b> instead of the corresponding mononuclear complex salt was shown to be driven by the gain in lattice enthalpy in the solid state. The bonding to Li⁺ in D₆ and 18-crown-6 metal complexes was described by a quantum theory of atoms in molecules (QTAIM) analysis to be mostly electrostatic while the bonding to Ag⁺ also had a significant charge transfer component. The charge transfer from both D₆ and 18-crown-6 to Ag⁺ and Li⁺ metal ions was depicted by the QTAIM analysis to be of similar strength, and the difference in the stabilities of the complexes was attributed mostly to more attractive electrostatic interactions between 18-crown-6 and the metal ions despite the more negative oxygen atomic charges calculated for D₆

Reactions of a Cyclodimethylsiloxane (Me₂SiO)₆ with Silver Salts of Weakly Coordinating Anions; Crystal Structures of [Ag(Me₂SiO)₆][Al] ([Al] = [FAl{OC(CF₃)₃}₃], [Al{OC(CF₃)₃}₄]) and Their Comparison with [Ag(18-Crown-6)]₂[SbF₆]₂

Two silver-cyclodimethylsiloxane cation salts [AgD₆]­[Al] ([Al] = [Al­(OR_F)₄]­(<b>1</b>) or [FAl­(OR_F)₃]­(<b>2</b>), R_F = C­(CF₃)₃, D = Me₂SiO) were prepared by the reactions of Ag­[Al] with D₆ in SO₂(l). For a comparison the [Ag­(18-crown-6)]₂[SbF₆]₂(<b>3</b>) salt was prepared by the reaction of Ag­[SbF₆] and 18-crown-6 in SO₂(l). The compounds were characterized by IR, multinuclear NMR, and single crystal X-ray crystallography. The structures of <b>1</b> and <b>2</b> show that D₆ acts as a pseudo crown ether toward Ag⁺. The stabilities and bonding of [MD_<i>n</i>]⁺ and [M­(18-crown-6)]⁺ (M = Ag, Li, <i>n</i> = 4–8) complexes were studied with theoretical calculations. The calculations predicted that D₆ adopts a puckered <i>C</i>_<i>i</i> symmetric structure in the gas phase in contrast to previous reports. 18-Crown-6 was calculated to bind more strongly to Li⁺ and Ag⁺ than D₆. ²⁹Si­[¹H] NMR results in solution, and calculations in the gas phase established that a hard Lewis acid Li⁺ binds more strongly to D₆ than Ag⁺. A comparison of the [MD_<i>n</i>]⁺ complex stabilities showed D₇ to form the most stable metal complexes in the gas phase and the solid state and explained why [AgD₇]­[SbF₆] was isolated in a previous reaction where ring transformations resulted in an equilibrium of [AgD_<i>n</i>]⁺ complexes. In contrast, the isolations of <b>1</b> and <b>2</b> were possible because the corresponding equilibrium of [AgD_<i>n</i>]⁺ complexes was not observed with [Al]⁻ anions. The formation of the dinuclear complex salt <b>3</b> instead of the corresponding mononuclear complex salt was shown to be driven by the gain in lattice enthalpy in the solid state. The bonding to Li⁺ in D₆ and 18-crown-6 metal complexes was described by a quantum theory of atoms in molecules (QTAIM) analysis to be mostly electrostatic while the bonding to Ag⁺ also had a significant charge transfer component. The charge transfer from both D₆ and 18-crown-6 to Ag⁺ and Li⁺ metal ions was depicted by the QTAIM analysis to be of similar strength, and the difference in the stabilities of the complexes was attributed mostly to more attractive electrostatic interactions between 18-crown-6 and the metal ions despite the more negative oxygen atomic charges calculated for D₆

Use of <i>F</i>-BODIPYs as a Protection Strategy for Dipyrrins: Optimization of BF₂ Removal

We recently reported the first general method for the deprotection of 4,4-difluoro-4-bora-3a,4a-diaza-<i>s</i>-indacenes (<i>F</i>-BODIPYs) involving a microwave-assisted procedure for the removal of the BF₂ moiety, and liberation of the corresponding free-base dipyrrin. Further optimization of the reaction has resulted in a more convenient and accessible protocol. The availability of this new methodology enables BF₂-complexation to be used as a dipyrrin protection strategy. Herein lies a detailed examination of the deprotection reaction, with a view to optimization and gaining mechanistic insight, and its application in facilitating a multistep synthesis of pyrrolyldipyrrins

Use of <i>F</i>-BODIPYs as a Protection Strategy for Dipyrrins: Optimization of BF₂ Removal

We recently reported the first general method for the deprotection of 4,4-difluoro-4-bora-3a,4a-diaza-<i>s</i>-indacenes (<i>F</i>-BODIPYs) involving a microwave-assisted procedure for the removal of the BF₂ moiety, and liberation of the corresponding free-base dipyrrin. Further optimization of the reaction has resulted in a more convenient and accessible protocol. The availability of this new methodology enables BF₂-complexation to be used as a dipyrrin protection strategy. Herein lies a detailed examination of the deprotection reaction, with a view to optimization and gaining mechanistic insight, and its application in facilitating a multistep synthesis of pyrrolyldipyrrins