Consecutive HDDA and TDDA reactions of silicon-tethered tetraynes for the synthesis of dibenzosilole-fused polycyclic compounds and their unique reactivity.

Silicon-tethered tetraynes possessing a 1,3-diyne moiety underwent consecutive hexadehydro- and tetradehydro-Diels-Alder reactions to give a series of fused polycyclic aromatic compounds containing a dibenzosilole skeleton. The benzene ring in the product acted as a 1,3-diene and reacted with the active alkyne as well as oxygen to provide [4 + 2] cycloadducts.

Intramolecular Consecutive Dehydro-Diels-Alder Reaction for the Catalytic and Enantioselective Construction of Axial Chirality.

Consecutive thermal and metal-catalyzed dehydro-Diels-Alder (DDA) reactions of sulfur-tethered tetraynes, possessing a 1,3-diyne moiety, proceeded efficiently, and axial chirality was achieved for the resulting dibenzothiophenyl moieties. Chiral-rhodium catalysis realized a highly enantioselective synthesis, and transformations into bis(benzocarbazole) derivatives were also achieved.

Sulfur-directed carbon-sulfur bond cleavage for Rh-catalyzed regioselective alkynylthiolation of alkynes.

Sulfur-directed sp C-S bond cleavage along with a regioselective reaction with alkynes proceeded to give (Z)-enyne sulfides in high to excellent yields. Mechanistic studies were conducted, including characterization of an intermediate. An intramolecular variant realized the construction of a dibenzodithiepin skeleton, which is a seven-membered ring with two sulfur atoms.

Catalytic and Enantioselective Synthesis of Chiral Multisubstituted Tribenzothiepins by Intermolecular Cycloadditions.

The first catalytic and highly enantioselective synthesis of tribenzothiepin derivatives was achieved. Two types of intermolecular cycloadditions using either diphenyl-sulfide-tethered diynes or 2-phenyl sulfanylbenzene-tethered diynes with a monoalkyne successfully gave chiral multisubstituted tribenzothiepins in good to excellent ee values under mild conditions. The inversion energy of this saddle-shaped molecule was calculated by measurement of the racemization rate of chiral tribenzothiepins using the Eyring kinetic equation under heating conditions. The present protocol could also be used to prepare a chiral tribenzoselenepin.