Synthesis Of Medium-sized Lactones Research Articles

Synthesis of Medium-Sized Lactones from Siloxy Alkynes and Lactols by Ring Expansion

Synthesis of Medium-Sized Lactones from Siloxy Alkynes and Lactols by Ring Expansion

Synthesis of medium-sized lactones from siloxy alkynes via ring expansion

Synthesis of medium ring lactones remains as a challenging topic in organic synthesis due to the disfavored kinetic and thermodynamic features. Herein we detail an efficient intermolecular process using siloxy alkynes as substrates and oxetene ring expansion as the key strategy. With extension to a new silyl-masked alkyne, this reaction now features a broad scope, high efficiency, and mild conditions.

Synthesis of medium-sized lactones by the copper(I)chloride/2,2′-bipyridine-catalyzed cyclization of di- and trichloroacetates

Medium-sized lactones (eight- to eleven-membered rings) are efficiently formed by Cu(bpy)Cl catalyzed cyclization of various alkenyl di- and trichloroacetates at temperatures between 80 and 190°C in 1,2-dichloroethane or benzene as solvents. The mechanism of the alkene addition reaction is best understood as a chlorine atom transfer process through radical type intermediates. Exclusive endo-cyclization is observed in all cases. Ten and eleven-membered lactones are only accessible by the ‘rigid chain’ approach, in which an alkyne or alkene function is incorporated in the chain connecting the reaction centres, thus reducing the flexibility of the molecule.

Synthesis of medium-sized lactones by copper(I) catalyzed atom transfer cyclization

Several ω-alkenyl dichloroacetates cyclize in moderate to excellent yields to 3,5-dichloro-oxocon-2-ones (8-membered ring lactones) when heated in benzene at 80–180 °C in the presence of a catalytic amount of the cuprous chloride 2,2′-bipyridine complex.

Synthesis of medium-sized lactones: Iodosobenzene diacetate an efficient reagent for β-fragmentation of alkoxy-radicals

Photolysis of several steroidal lactols in the presence of iodosobenzene diocetate (IBDA) and iodine leads to alkoxy-radicals, which undergo β-fragmentation to produce medium-sized lactones in good yields.

New general synthesis of medium-sized lactones: A new entry tothe synthesis of (+−)-phoracantholide I [(+−)-decan-9-olide

We describe a new general method for the synthesis ofmedium-sized lactones under mild conditions involving β-scissionof alkoxy radicals derived from catacondensed lactols as a key stepand its application to an efficient new synthesis of a naturallyoccurring 10-membered lactone, phoracantholide I[(+−)-decan-9-olide].