Domino Formation of Enamines - Intramolecular Cyclizations to 1‑Aminotetralins from γ‑Arylallene Aldehydes and Amines

1,5-/1,6-Allenals conjugated to an aromatic ring undergo a cyclization, in the presence of an amine, that leads to tricyclic compounds including the 1-aminotetralin scaffold. This domino process combines the <i>in situ</i> formation of the enamine and the cyclization affording the tricyclic 1-aminotetralins in very high diastereoselectivities

α‑Fused Dithienyl BODIPYs Synthesized by Oxidative Ring Closure

Both symmetrical and unsymmetrical α-fused dithienyl-BODIPY dyes have been prepared by oxidative ring closure induced by anhydrous FeCl₃. Extension of the π-system in the fused BODIPY leads to a progressive shift to 579 and 665 nm respectively for the absorption wavelength maxima of the mono- and difused dyes relative to the unfused species (λ_abs = 502 nm). Linking such dyes to an NIR emitting module provides a panchromatic chromophore with a large absorption cross section in the visible range associated with efficient intramolecular cascade energy transfer

Catalytic Enantioselective Vinylogous Mukaiyama–Michael Addition of 2‑Silyloxyfurans to Cyclic Unsaturated Oxo Esters

The copper-catalyzed asymmetric addition of 2-silyloxyfurans to cyclic unsaturated oxo esters is reported. The reaction proceeds with excellent diastereocontrol (usually dr 99:1) and modest to high enantioselectivity, depending on the nature of the ester group and the substitution of the cyclic oxo ester. We have shown that these substrates can be transformed into a variety of building blocks bearing a γ-butenolide or γ-lactone connected to a cycloalkane or cycoalkene moiety

Diastereoselective Synthesis of Planar Chiral Phosphoramidites with a Ferrocenophane Scaffold

A new family of planar chiral phosphoramidites with a [3]­ferrocenophane structure was synthesized. The synthetic strategy involved diastereoselective formation of the chiral ferrocene units from suitable substituted bis-cyclopentadienyl derivatives. Preliminary coordination studies of these ligands were undertaken with the synthesis of palladium and platinum complexes

A Simple and Straightforward Approach to Quinoxalines by Iron/Sulfur-Catalyzed Redox Condensation of <i>o</i>‑Nitroanilines and Phenethylamines

<i>In situ</i> generated iron sulfide from elemental sulfur and ferric chloride was found to be a highly efficient catalyst for the redox condensation cascade reaction between <i>o</i>-nitroanilines and 2-arylethylamines. This method constitutes a new atom-, step-, and redox-economical route to 2-arylquinoxalines

Cation Clock Permits Distinction Between the Mechanisms of α- and β‑O- and β‑C-Glycosylation in the Mannopyranose Series: Evidence for the Existence of a Mannopyranosyl Oxocarbenium Ion

The use of a cationic cyclization reaction as a probe of the glycosylation mechanism has been developed and applied to the 4,6-<i>O</i>-benzylidene-protected mannopyranoside system. Cyclization results in the formation of both cis- and trans-fused tricyclic systems, invoking an intermediate glycosyl oxocarbenium ion reacting through a boat conformation. Competition reactions with isopropanol and trimethyl­(methallyl)­silane are interpreted as indicating that β-O-mannosylation proceeds via an associative S_N2-like mechanism, whereas α-O-mannosylation and β-C-mannosylation are dissociative and S_N1-like. Relative rate constants for reactions going via a common intermediate can be estimated

Catalytic Enantioselective Vinylogous Mukaiyama–Michael Addition of 2‑Silyloxyfurans to Cyclic Unsaturated Oxo Esters

The copper-catalyzed asymmetric addition of 2-silyloxyfurans to cyclic unsaturated oxo esters is reported. The reaction proceeds with excellent diastereocontrol (usually dr 99:1) and modest to high enantioselectivity, depending on the nature of the ester group and the substitution of the cyclic oxo ester. We have shown that these substrates can be transformed into a variety of building blocks bearing a γ-butenolide or γ-lactone connected to a cycloalkane or cycoalkene moiety

Synthesis of Highly Functionalized BOPHY Chromophores Displaying Large Stokes Shifts

BOPHY dyes bearing bromo (in 5,5′-position) and iodo (in 4,4′-position) were synthesized. Double Knoevenagel reactions allow the extension of conjugation, resulting in an absorption above 625 nm. Selective cross-coupling reactions promoted by palladium(0) and microwave irradiation allow linking of a perylene module. These dyes are highly fluorescent, and the intramolecular cascade energy transfer from the perylene moiety to the BOPHY framework is almost quantitative, providing large virtual Stoke shifts (>5100 cm^–1)

Triphenylphosphine Photorelease and Induction of Catalytic Activity from Ruthenium-Arene Complexes Bearing a Photoswitchable <i>o</i>‑Tosylamide Azobenzene Ligand

The reactivity of cationic arene ruthenium complexes bearing a photoswitchable <i>o</i>-tosylamide azobenzene ligand toward various phosphorus nucleophiles was investigated. The resulting phosphine-ruthenium complexes containing an azobenzene ligand were isolated as the <i>Z</i> isomer. Under appropriate reaction conditions, quantitative triphenylphosphine photorelease from the complex was achieved through <i>Z</i> → <i>E</i> isomerization of the ligand. This process was applied to the photoinitiation of the catalytic aza-Morita–Baylis–Hillman reaction

Triphenylphosphine Photorelease and Induction of Catalytic Activity from Ruthenium-Arene Complexes Bearing a Photoswitchable <i>o</i>‑Tosylamide Azobenzene Ligand

The reactivity of cationic arene ruthenium complexes bearing a photoswitchable <i>o</i>-tosylamide azobenzene ligand toward various phosphorus nucleophiles was investigated. The resulting phosphine-ruthenium complexes containing an azobenzene ligand were isolated as the <i>Z</i> isomer. Under appropriate reaction conditions, quantitative triphenylphosphine photorelease from the complex was achieved through <i>Z</i> → <i>E</i> isomerization of the ligand. This process was applied to the photoinitiation of the catalytic aza-Morita–Baylis–Hillman reaction