Conversion of polyfunctional nitroalkanes into carbonyl compounds synthesis of the pheromone chalcogran and of key building blocks for the macrolides pyrenophorin and vermiculine

Starting from nitroalkane adducts of the general structure 3, several versions of the Nef reaction are performed. The reagent combination H2O2/K2CO3 turned out to be the most useful in liberating the carbonyl group because of toleration of acid‐sensitive functionalities. Other methods provide the acetal 5, diketone 7, γ‐lactones 8 and 9, or the chlorinated nitro compound 13, respectively. Cyclization of the highly functionalized diketone 18 gives cyclopentenone derivative 19. Trifunctional and tetrafunctional intermediates 12 and 17 can be transformed into 20 and 21 by reduction and silylation. These compounds are known or conceivable precursors for the antibiotic macrolides pyrenophorin and vermiculine, respectively. Nitroalkane 22 affords within a few simple steps the aggregation pheromone chalcogran 24. The synthetic paths are discussed with regard to efficiency and flexibility.