Bioinspired, base- and metal-free, mild decarboxylative aldol activation of malonic acid half thioesters under phase-transfer reaction conditions

Utilizing ‘off the shelf’ commercially available, cheap, small synthetic molecules that mimic the efficient mediation of important bioreactions utilized by Nature is not only highly sought after but also currently highly topical. This paper details our preliminary efforts at developing a unique base- and metal-free phase-transfer-mediated malonic acid thioester (MAHT) ‘activation protocol’ that efficiently generates (±)-β-thioesters. Our bioinspired aldol process is exceptionally mild, conducted under near neutral pH reaction conditions, does not require an inert, oxygen-free atmosphere or anhydrous reaction conditions and is highly atom-economic. Exemplifying the utility of our protocol, the synthesis of an array of structurally and functionally diverse (±)-β-hydroxy thioesters equipped with highly prized functionality, i.e., chlorine, bromine, fluorine, nitrile and nitro groups, is reported, as is the diastereoselective potential of this important reaction.