Stable vinyl cations. Direct spectroscopic observation of vinyl-substituted vinyl cations

Remote C-H insertion of vinyl cations leading to cyclopentenones.

We report a Lewis acid catalyzed reaction sequence involving a 1,2-shift and subsequent C-H insertion that gives monocyclic and fused bicyclic cyclopentenone products. This reaction sequence, which is initiated by treating β-hydroxy-α-diazo ketones with a Lewis acid, proceeds through vinyl cation intermediates that insert at non-activated gamma C-H bonds. This reaction represents an alternative...

Reactions of Substituted Vinyl Cations in Acetonitrile Solution as Studied by Flash Photolysis

Vinyl cations I+, of the structure R^C^CR" (I+: R' = R" = anisyl; R' = phenyl.R" = anisyl. I*: R' — methyl.R" = anisyl) were generated by flash photolysis of corresponding bromides. Lifetime measurements yielded the following: substitution of aromatic groups in 2-position by methyl groups largely improved the electrophilicity of the vinyl cations. The nucleophilicity of typical compounds (keton...

Vinyl Cations Substituted with β π-Donors Have Triplet Ground States

Computations at the CASPT2, CBS-QB3, and B3LYP levels of theory demonstrate that -substitution of vinyl cations with π-donors switches the ground state of these ions from the familiar closedshell singlet state to a carbene-like triplet state similar to the electronic state of triplet phenyl cations. Although the parent vinyl cation is a ground-state singlet species with a very large energy gap ...

Vinyl cations substituted with beta pi-donors have triplet ground states.

Computations at the CASPT2, CBS-QB3, and B3LYP levels of theory demonstrate that beta-substitution of vinyl cations with pi-donors switches the ground state of these ions from the familiar closed-shell singlet state to a carbene-like triplet state similar to the electronic state of triplet phenyl cations. Although the parent vinyl cation is a ground-state singlet species with a very large energ...

Vinyl Acetate