An efficient, organocatalytic, and ecofriendly method has been developed for the quick construction of a wide array of 3,3-disubstituted oxindoles in good to excellent yields and diastereomeric ratio (up to ≤96:4) with excellent functional group tolerance via an allylic alkylation reaction of cyclic sulfamidate imines with a number of MBH carbonates of isatins in 2-MeTHF as an environmentally benign solvent at room temperature using 5 mol % of DABCO. Furthermore, a metal-free-based one-shot synthesis of a medicinally promising polycyclic spirooxindole with an all-carbon spirocenter has been achieved with outstanding dr value (up to ≤99:1).

A stereo- and chemoselective ring closing reaction of N-sulfonyl ketimines with ethene sulfonyl fluorides promoted by DBU is reported. This selective C–C vs. C–N bond cyclization process delivers to trans-cyclopropanes (dr up to ≤99 : 1) and fused-dihydropyrroles.

The present paper reports an efficient, organocatalytic, environmentally friendly and stereoselective [3+3] one‐pot allylic alkylation/oxa‐Michael reaction by involving a wide range of Morita–Baylis–Hillman (MBH) carbonates of isatins and several pharmacologically attractive enolizable C−H activated cyclic carbonyl compounds such as 1,3‐binucleophiles, namely pyrazolones, isoxazolones, 4‐hydroxyxoumarins, 4‐hydroxy‐6‐methyl‐α‐pyrone, lawsone and dimedone in a biomass‐derived 2‐MeTHF as green solvent catalyzed by DABCO as a solid Lewis‐base catalyst. This protocol delivers a unique class of medicinally promising spirooxindole‐fused‐dihydropyran scaffolds.

DBU-catalyzed spiro-annulation and concomitant ring expansion/domino reaction of δ-acetoxy allenoates with cycl-2-ene-N-sulfonyl hydrazides afford ring-expanded (5 → 6, 6 → 7, and 7 → 8) products. By contrast, cycl-3-ene/ane-N-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. An extension to (R)-(−)-carvone-derived sulfonyl hydrazide also led to ring expansion and gave pyrazoloazepine.

Under metal-free conditions, δ-acetoxy allenoates react with cyclic N-sulfonyl imines (sulfamidate imines/sulfonyl imines) to afford functionalized 2-pyridinyl acetates (α-pyridyl acetates) or teraryl motifs by a simple Lewis base switch. Thus, while DBU/Na 2 CO 3 combination-directed [3 + 3] annulation involves sulfonyl elimination via O−S or C−S bond cleavage, affording 2-pyridinyl acetates, Ph 3 P-catalyzed [4 + 2] annulation leads to functionalized teraryls via Mannich coupling and C−N bond cleavage with retention or cleavage of the sulfamoyloxy group depending on the reaction conditions.