14 research outputs found
Can acyclic conformational control be achieved via a sulfur-fluorine gauche effect?
The gauche conformation of the 1,2-difluoroethane motif is known to involve stabilising hyperconjugative interactions between donor (bonding, ĎC-H) and acceptor (antibonding, Ď*C-F) orbitals. This model rationalises the generic conformational preference of F-Cβ-CÎą-X systems (ĎFCCX â 60°), where X is an electron deficient substituent containing a Period 2 atom. Little is known about the corresponding Period 3 systems, such as sulfur and phosphorus, where multiple oxidation states are possible. Conformational analyses of β-fluorosulfides, -sulfoxides and -sulfones are disclosed here, thus extending the scope of the fluorine gauche effect to the 3rd Period (F-C-C-S(O) n ; ĎFCCS â 60°). Synergy between experiment and computation has revealed that the gauche effect is only pronounced in structures bearing an electropositive vicinal sulfur atom (S+-O-, SO2)
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Can acyclic conformational control be achieved via a sulfur-fluorine gauche effect?
The gauche conformation of the 1,2-difluoroethane motif is known to involve stabilising hyperconjugative interactions between donor (bonding, ĎC-H) and acceptor (antibonding, Ď*C-F) orbitals. This model rationalises the generic conformational preference of F-Cβ-CÎą-X systems (ĎFCCX â 60°), where X is an electron deficient substituent containing a Period 2 atom. Little is known about the corresponding Period 3 systems, such as sulfur and phosphorus, where multiple oxidation states are possible. Conformational analyses of β-fluorosulfides, -sulfoxides and -sulfones are disclosed here, thus extending the scope of the fluorine gauche effect to the 3rd Period (F-C-C-S(O) n ; ĎFCCS â 60°). Synergy between experiment and computation has revealed that the gauche effect is only pronounced in structures bearing an electropositive vicinal sulfur atom (S+-O-, SO2)
Deconstructing the Catalytic, <i>Vicinal</i> Difluorination of Alkenes: HF-Free Synthesis and Structural Study of <i>p</i>âTolIF<sub>2</sub>
Recently, contemporaneous strategies
to achieve the <i>vicinal</i> difluorination of alkenes
via an IÂ(I)/IÂ(III) catalysis manifold
were independently reported by this laboratory and by Jacobsen and
co-workers. Both strategies proceed through a transient ArIÂ(III)ÂF<sub>2</sub> species generated by oxidation of the ArI catalyst. Herein,
an efficient synthesis of <i>p</i>-TolIF<sub>2</sub> from <i>p</i>-TolI and Selectfluor is presented, together with a crystallographic
and spectroscopic study. To mitigate safety concerns and simplify
reaction execution, an HF-free protocol was devised employing CsF
as a substitute fluoride source. The study provides insight into the
initial IÂ(I)âIÂ(III) oxidation stage of the catalytic protocol
using Selectfluor
The SulfurâFluorine <i>Gauche</i> Effect in Coinage-Metal Complexes: Augmenting Conformational Equilibria by Complexation
Controlling
the rotation about unhindered CÂ(sp<sup>3</sup>)âCÂ(sp<sup>3</sup>) bonds by simple structural changes has obvious benefits
in molecular design. While the avoidance of nonbonding interactions
remains one of the cornerstones of acyclic conformational control,
stabilizing stereoelectronic effects have the added benefit that conformer
populations can be fine-tuned by augmenting or diminishing the central
interaction. Strategies may include adjusting the oxidation state
of a substituent or reversible formation of a complex to modulate
MO levels. In the case of the sulfurâfluorine <i>gauche</i> effect, the propensity of the SâCâCâF motif
to adopt a <i>synclinal</i> arrangement (Ό<sub>FCCS</sub> = 60°), the conformer population distribution of the three
dominant rotamers partitioned by 120° can be biased by oxidation
of the S atom. Motivated by the importance of sulfur-based ligands
in main structural chemistry, the sulfurâfluorine <i>gauche</i> effect was translated to an organometallic paradigm as a potential
tool to achieve structural preorganization. This would allow the influence
of coinage-metal complexation on conformer population to be initially
assessed. The synthesis and characterization of a model goldÂ(I) and
silverÂ(I) metal complex featuring a ligand system containing a freely
rotatable SCCF motif is disclosed. In both complexes, the title stereoelectronic
effect manifests itself in the expected conformation, with the <i>synclinal</i>-<i>endo</i> conformer being preferred.
This was corroborated by X-ray crystallography and DFT analysis, and
the molar fraction of rotamers was extrapolated from a detailed solution-phase
NMR spectroscopic analysis. Complexation was found to reinforce the
sulfurâfluorine <i>gauche</i> effect
The SulfurâFluorine <i>Gauche</i> Effect in Coinage-Metal Complexes: Augmenting Conformational Equilibria by Complexation
Controlling
the rotation about unhindered CÂ(sp<sup>3</sup>)âCÂ(sp<sup>3</sup>) bonds by simple structural changes has obvious benefits
in molecular design. While the avoidance of nonbonding interactions
remains one of the cornerstones of acyclic conformational control,
stabilizing stereoelectronic effects have the added benefit that conformer
populations can be fine-tuned by augmenting or diminishing the central
interaction. Strategies may include adjusting the oxidation state
of a substituent or reversible formation of a complex to modulate
MO levels. In the case of the sulfurâfluorine <i>gauche</i> effect, the propensity of the SâCâCâF motif
to adopt a <i>synclinal</i> arrangement (Ό<sub>FCCS</sub> = 60°), the conformer population distribution of the three
dominant rotamers partitioned by 120° can be biased by oxidation
of the S atom. Motivated by the importance of sulfur-based ligands
in main structural chemistry, the sulfurâfluorine <i>gauche</i> effect was translated to an organometallic paradigm as a potential
tool to achieve structural preorganization. This would allow the influence
of coinage-metal complexation on conformer population to be initially
assessed. The synthesis and characterization of a model goldÂ(I) and
silverÂ(I) metal complex featuring a ligand system containing a freely
rotatable SCCF motif is disclosed. In both complexes, the title stereoelectronic
effect manifests itself in the expected conformation, with the <i>synclinal</i>-<i>endo</i> conformer being preferred.
This was corroborated by X-ray crystallography and DFT analysis, and
the molar fraction of rotamers was extrapolated from a detailed solution-phase
NMR spectroscopic analysis. Complexation was found to reinforce the
sulfurâfluorine <i>gauche</i> effect
The SulfurâFluorine <i>Gauche</i> Effect in Coinage-Metal Complexes: Augmenting Conformational Equilibria by Complexation
Controlling
the rotation about unhindered CÂ(sp<sup>3</sup>)âCÂ(sp<sup>3</sup>) bonds by simple structural changes has obvious benefits
in molecular design. While the avoidance of nonbonding interactions
remains one of the cornerstones of acyclic conformational control,
stabilizing stereoelectronic effects have the added benefit that conformer
populations can be fine-tuned by augmenting or diminishing the central
interaction. Strategies may include adjusting the oxidation state
of a substituent or reversible formation of a complex to modulate
MO levels. In the case of the sulfurâfluorine <i>gauche</i> effect, the propensity of the SâCâCâF motif
to adopt a <i>synclinal</i> arrangement (Ό<sub>FCCS</sub> = 60°), the conformer population distribution of the three
dominant rotamers partitioned by 120° can be biased by oxidation
of the S atom. Motivated by the importance of sulfur-based ligands
in main structural chemistry, the sulfurâfluorine <i>gauche</i> effect was translated to an organometallic paradigm as a potential
tool to achieve structural preorganization. This would allow the influence
of coinage-metal complexation on conformer population to be initially
assessed. The synthesis and characterization of a model goldÂ(I) and
silverÂ(I) metal complex featuring a ligand system containing a freely
rotatable SCCF motif is disclosed. In both complexes, the title stereoelectronic
effect manifests itself in the expected conformation, with the <i>synclinal</i>-<i>endo</i> conformer being preferred.
This was corroborated by X-ray crystallography and DFT analysis, and
the molar fraction of rotamers was extrapolated from a detailed solution-phase
NMR spectroscopic analysis. Complexation was found to reinforce the
sulfurâfluorine <i>gauche</i> effect