cis-2,6-Tetrahydropyran is an important structural skeleton of bioactive natural products. A facile synthesis of cis-2,6-disubstituted-3,6-dihydropyrans as cis-2,6-tetrahydropyran precursors has been achieved in high regio- and stereoselectivity with high yields. This reaction involves a palladium-catalyzed decarboxylative allylation of various 3,4-dihydro-2H-pyran substrates. Extending this reaction to 1,2-unsaturated carbohydrates allowed the achievement of challenging β-C-glycosylation. Based on this methodology, the total syntheses of (±)-centrolobine and (+)-decytospolides A and B were achieved in concise steps and overall high yields.

The synthesis of α,α-diacylaziridines and α,α,β-triacylaziridines from reaction of 2-alkyl-substituted-1,3-dicarbonyl compounds and 2-acyl-substituted-1,4-dicarbonyl compounds with arylsulfonyliminoiodinanes (ArSO2N=IPh) under Brønsted base-mediated atmospheric conditions is described. The reaction mechanism is thought to involve the formal oxidation of the substrate followed by aziridination of the ensuing α,β-unsaturated intermediate by the hypervalent iodine(iii) reagent.

Facile Access to cis-2,6-Disubstituted Tetrahydropyrans by Palladium-Catalyzed Decarboxylative Allylation: Total Syntheses of ()-Centrolobine and (+)-Decytospolides A and B. -Application of this method is demonstrated by the total syntheses of Centrolobine (VI) and Decytospolides A and B (VII). -(ZENG, J.; TAN, Y. J.; MA, J.; LEOW, M. L.; TIRTORAHARDJO, D.; LIU*, X.-W.; Chem. -Eur. J. 20 (2014) 2, 405-409, http://dx.