Abstract

A diastereoselective reaction of 3-methyl-1H-phenalen-1-one (6) with Lawessons reagent afforded 8a,15a-dihydro-7,8a,16-trimethyl-7,16-epoxy-7H,15H,16H-naphtho[1,8-ef]phenaleno[1,2-b]oxocin-15-one (10), in 82% yield. The formation mechanism of 10 involves a Michael addition of a naphthopyrane intermediate to 6, followed by an intramolecular aldol condensation. The structure of a single enantiomer of 10 (7R, 8aR, 15aR, 16S or 7S, 8aS, 15aS, 16R) was elucidated by X-ray crystallography.

Keywords: phenalenes, novel aromatic chemistry, diastereoselective reaction, chirality, lawessons reagent, x-ray crystallography