Accessing skeletal diversity using catalyst control: formation of n and n + 1 macrocyclic triazole rings.

A regioselective intramolecular Huisgen cycloaddition was performed on various azido alkyne substrates giving rise to macrocyclic triazole rings. Using catalyst control, a common intermediate has been converted to two structurally unique macrocycles with either a 1,5- or a 1,4-triazole resulting in an n or n + 1 ring size. This is the first example of an intramolecular ruthenium-catalyzed Huisgen cycloaddition.

Phase-vanishing halolactonization of neat substrates.

Phase-vanishing reactions are triphasic reactions which involve a reagent, a liquid perfluoroalkane as a phase screen and a substrate. The perfluoroalkane does not dissolve any of the reactants and is used to separate them. Halolactonization of neat substrates under phase-vanishing conditions avoids use of both solvents and basic reaction conditions. Both gamma,delta-alkenoic acids as well as the corresponding methyl esters are suitable substrates for phase-vanishing halolactonizations. The reaction works well both on solid and liquid substrates and the products are obtained in good to excellent yields, particularly in the case of rigid bicyclic systems. Bromine (Br(2)) and iodine monochloride (ICl) are suitable electrophiles for bromolactonization and iodolactonization, respectively. Although in some cases iodine gave satisfactory yields of the corresponding iodolactone, it is generally inferior to iodine monochloride.