Synthesis of 2,2-functionalized benzo[1,3]dioxoles

Easy and direct conversion of tosylates and mesylates into nitroalkanes

Tosylates and mesylates were directly converted into the corresponding nitroalkanes, by their treatment with tetrabutylammonium nitrite (TBAN) under mild conditions.

Understanding the regioselectivity in Scholl reactions for the synthesis of oligoarenes

A short reaction sequence leads to oligoarene derivatives utilising a regioselective Scholl reaction for the unprecedented cyclisation to the mono-functionalised oligoarene under methanol elimination. Quantum-chemical investigations reveal the reason for the remarkably high regioselectivity.

Phosphine-initiated general base catalysis: facile access to benzannulated 1,3-diheteroatom five-membered rings via double-Michael reactions of allenes

General base-catalyzed double-Michael reactions of allenes with various dinucleophiles are described. The reactions are facilitated most efficiently by a catalytic amount of trimethylphosphine, affording six types of C2-functionalized benzannulated five-membered heterocycles: benzimidazolines, benzoxazolines, benzothiazolines, 1,3-benzodioxoles, 1,3-benzoxathioles, and 1,3-benzodithioles. This atom-economical reaction is operationally simple and provides the product heterocycles in good to excellent yields. Careful mechanistic studies unveiled the phosphine-triggered general base catalysis pathway. Furthermore, the double-Michael reaction can serve as an alternative method for the selective monoketalization of β-diketones.

The imidato-alkenyllithium route for the synthesis of the isoquinocycline-pyrrolopyrrole substructure

A convergent and effective synthesis of the pyrrolopyrrole substructure (CDEFG) of the isoquinocyclines is reported. A key step is a tin-lithium exchange of an imidato-alkenyltin compound (a ring G equivalent) and the subsequent acylation with a lactone. The resulting acetal is used successfully for the ring F closure to the pyrrolopyrrole. The sole formation of the isoquinocycline N,O-acetal epimer is in accordance with the proposed mechanism for the isomerization of quinocyclines to isoquinocyclines.