Derailed Ohira-Bestmann Reaction of γ,δ-Unsaturated Aldehydes for the Stereoselective Synthesis of Cyclopenta[c]pyrazoles

The synthesis of cyclopenta[c]pyrazoles from γ,δ-unsaturated aldehydes by a domino sequence involving one-carbon homologation and intramolecular azomethine imine 1,3-dipolar cycloaddition is disclosed. The fused pyrazoles bearing aromatic and aliphatic substituents are obtained in good yields and excellent diastereomeric purity. Additionally, the synthetic utility of the pyrazole products generated by this method has been highlighted in a series of functionalization reactions. The method presented opens strategic opportunities for the synthesis of pyrazole-containing biologically active compounds.     

Solvent effects in the reaction between (anthracen‐9‐yl)methyl sulfides and electron‐deficient acetylenes

Solvent‐dependent diverse reactivity of (anthracen‐9‐yl)methyl sulfides with a few electron‐deficient acetylenes is described. Diversity in reactivity is attributed to competition between one electron transfer, two electron transfer and Diels–Alder reaction of these sulfides with electron‐deficient acetylenes. We have proposed plausible mechanisms to account for various reactions observed by us. Copyright © 2015 John Wiley & Sons, Ltd.