1,2-Bisanionic coupling approach to 2,3-disubstituted cyclopentenols and cyclopentenones

[reaction: see text] We describe a new approach to 2,3-disubstituted cyclopentenols and cyclopentenones through two consecutive regioselective additions of equal or different electrophiles to a cyclopentene bisanionic synthon. Indeed, on exposure to BuLi, 3-bromo-2-iodocyclopent-2-enol O-TBS ether undergoes iodine-lithium permutation with complete regioselectivity. Successive reaction of the monolithium anion with different C(sp(2))- and C(sp(3))-electrophiles affords the corresponding 2-substituted-3-bromocyclopentenol derivative. Subsequent bromo-lithium exchange with t-BuLi, followed by reaction with an equal or different electrophile, affords the desired 2,3-disubstituted cyclopentenol.     

Transition Metal Promoted Cascade Heterocycle Synthesis through C−H Functionalization

Sequential, domino and tandem reactions could be defined as a sequence of synthetic transformations that occur one after the other, in the same reaction flask. This Review highlights recent advances at the overlap of two worlds: transition-metal mediated C−H activation as a trigger of cascade reaction, for the heterocycles synthesis. To shed some light on this intricate “middle-earth”, focus was put on the reaction mechanism rather than the type of metal or the chronological order of the reaction. The aim is to separate, and then highlight, the true domino reactions initiated by C−H activation, compared to other examples of C−H functionalization for heterocycle syntheses.     

The role of local thermal non-equilibrium in modelling smouldering combustion of organic liquids

A one-dimensional numerical model of smouldering combustion was developed in order to better understand smouldering and accurately predict forced, upwards, self-sustained smouldering for the purposes of treating hydrocarbon-contaminated soil. The role of local thermal non-equilibrium was explored via a new heat transfer correlation obtained specifically for conditions typical of smouldering hydrocarbon-contaminated soil. The model was calibrated to a smouldering experiment and then confidence in the model was gained by independent simulations of additional experiments. The smouldering chemistry was represented by a two-step kinetic mechanism, with the results indicating that this simple framework was sufficient to reproduce the main features of self-sustained smouldering. Local thermal non-equilibrium was demonstrated to be significant in smouldering, with an average normalized temperature difference of 36% between the air and the sand/fuel. Moreover, incorporating the new non-equilibrium correlation provided accurate predictions, particularly in the heat transfer-dominated regions preceding and trailing the front. Results further demonstrated that the most widely used correlation in the literature effectively ensures local thermal equilibrium and such models could not reproduce the experiments.