One-pot synthesis of [6-5-6] tricyclic products via a double Diels-Alder/Nazarov tandem reaction of unsymmetrically substituted cross-conjugated diynones

Chiral Teropyrenes: Synthesis, Structure, and Spectroscopic Studies

We present the inaugural synthesis of a chiral teropyrene achieved through a four-fold alkyne benzannulation catalyzed by InCl3, resulting in good yields. The product underwent thorough characterization using FT-Raman and FT-IR spectroscopies, demonstrating a close agreement with calculated spectra. X-ray crystallographic analysis unveiled a notable twist in the molecule's backbone, with an end-to-end twist angle of 51°, consistent with computational predictions. Experimentally determined enantiomeric inversion barriers revealed a significant energy barrier of 23 kcal/mol, facilitating the isolation of enantiomers for analysis by circular dichroism (CD) and circularly polarized luminescence (CPL) spectroscopies. These findings mark significant strides in the synthesis and characterization of chiral teropyrenes, offering insights into their structural and spectroscopic properties.

Atom-Economic Synthesis of Highly Functionalized Bridged Ring Systems Initiated by Ring Expansion of Indene-1,3-dione

An atom economic procedure for the regioselective synthesis of bridged seven-membered-ring compounds from simple reactants such as ynones and indene-1,3-dione has been developed. This process was realized through the one-pot reactions of ring-expansion of indene-1,3-dione with alkynyl ketones and successive formal [4+2] cycloaddition. The Michael addition reaction is the key for the regioselectivity of the formal [4+2] cycloaddition.

One-Pot Domino Friedel-Crafts Acylation/Annulation between Alkynes and 2-Methoxybenzoyl Chlorides: Synthesis of 2,3-Disubstituted Chromen-4-one Derivatives

A highly regioselective synthesis of 2,3-disubstituted chromen-4-one derivatives is accomplished from readily available internal alkynes and 2-methoxybenzoyl chlorides. The reaction proceeds via a domino intermolecular Friedel-Crafts acylation/intramolecular vinyl carbocation trapping (or oxa-Michael addition)/demethylation reaction sequence. This Lewis acid promoted method features relatively mild reaction conditions to synthesize a variety of 2,3-disubstituted chromen-4-one derivatives in one pot with up to 93% yield. The chromen-2-one (coumarin) product was obtained when 2,6-dimethoxybenzoyl chloride was used as a starting material via an electrophilic aromatic substitution/rearrangement process.