Synthesis of five- and six-membered heterocycles by dimethyl carbonate with catalytic amounts of nitrogen bicyclic bases. Issue 2 (24th November 2014) - Aricò, F.
Abstract : Five- and six-membered N- and O-heterocycles have been prepared by DMC chemistry in the presence of catalytic amounts of a homogeneous nitrogen bicyclic base under neat conditions. Abstract : A catalytic amount of a nitrogen bicyclic base, i.e., DABCO, DBU or TBD, is effective for the one-pot synthesis of heterocycles from 1, 4-, 1, 5-diols and 1, 4-bifunctional compounds via dimethyl carbonate chemistry under neat conditions. Nitrogen bicyclic bases that were previously shown to have enhanced the reactivity of DMC in methoxycarbonylation reaction by a BAc 2 mechanism are herein used for the first time as efficient catalysts for cyclization reactions encompassing both BAc 2 and BAl 2 pathways. This synthesis procedure was also applied to a large scale synthesis of cyclic sugars, isosorbide and isomannide, starting fromd -sorbitol andd -mannitol, respectively. The resulting anhydro sugar alcohols were obtained as pure crystalline compounds that did not require any further purification or crystallization.