DBU-Catalyzed Ring Expansion or Ene-amine Formation Involving δ-Acetoxy Allenoates and -Sulfonyl Hydrazides.

DBU-catalyzed spiro-annulation and concomitant ring expansion/domino reaction of δ-acetoxy allenoates with cycl-2-ene--sulfonyl hydrazides afford ring-expanded (5 → 6, 6 → 7, and 7 → 8) products. By contrast, cycl-3-ene/ane--sulfonyl hydrazones under similar conditions deliver pyrazole cores with the same allenoate that involves allylic elimination in which δ-acetoxy allenoate serves as 3C-synthon. The key spirocyclic intermediates, as well as dienyl-amine intermediates, are isolated and characterized.

Pd-catalysed intramolecular transformations of indolylbenzenesulfonamides: -sulfonamido-bi(hetero)aryls C2-arylation and polycyclic sultams C3 arylation.

Palladium-catalysed and base-dependent intra-molecular -substitution and cyclisation strategies involving -indolyl-substituted aryl-sulfonamides for the rapid construction of 2-aryl indole and indole-fused six-membered sultams are described. The Pd(OAc)/PhP/EtN combination delivers indolyl C2 arylated motifs C(2)-N bond cleavage followed by C-C bond formation. In sharp contrast to this, the Pd(OAc)/PhP/KCO combination induced intramolecular-Heck cross-coupling affords polycyclic sultams exclusively.

Pyridine vs DABCO vs TBAB in Annulations of δ-Acetoxy Allenoates with Thioamides Leading to Dihydrothiophene, Thiopyran, and Thiazole Scaffolds.

The same δ-acetoxy allenoates and thioamides, under DABCO, pyridine, or tetra--butyl ammonium bromide (TBAB) catalysis, undergo distinctly different annulations giving chemoselective routes to dihydrothiophene, thiopyran, or thiazole motifs. Thus, using pyridine in [3 + 2] annulation, dihydrothiophenes are obtained as . By contrast, under DABCO catalysis, allenoates deliver thiopyran motifs in good to high yields through cyclization.