Tortajada Research Group has published a new article in journal Chemistry Europe titled, “Alkali-Metal Base Catalyzed Electrocyclization of Isoprene Derivatives”. 

For more information: https://chemistry-europe.onlinelibrary.wiley.com/doi/epdf/10.1002/chem.71057

Abstract

The catalytic electrocyclization of heptatrienes represents an attractive strategy to access seven-membered carbocycles from acyclicprecursors, whose medium-size cyclic saturated hydrocarbon counterparts display physicochemical properties of interest forjet-fuel applications. Here we uncover the potential of alkali-metal amides to enable an efficient, high-yielding and multigram-scale electrocyclization of biobased ocimene and related trienes derived from isoprene. Experimental results show that both thenature of alkali metal (Li vs Na) and coordination by PMDETA (N,N,N′,N″,N″-pentamethyldiethylenetriamine) play a decisiverole in enabling efficient turnovers. Trapping and structural authentication of key metalated intermediates, together withDFT calculations, provide valuable mechanistic insights into the cyclization pathway and the factors governing reactivity. Thetransformation can proceed catalytically at relatively low loadings in neat conditions, with lithium-based catalysis providingselectively 1,1,4-trimethylcycloheptadienes albeit at higher catalyst loadings of 10 mol%, whereas sodium-based systems canoperate at lower loadings of 2 mol% and can promote the isomerization/cyclization of other trienes.