Lipase-catalyzed esterification in water enabled by nanomicelles. Applications to 1-pot multi-step sequences

Esterification in an aqueous micellar medium is catalyzed by a commercially available lipase in the absence of any co-factors. The presence of only 2 wt% designer surfactant, TPGS-750-M, assists in a 100% selective enzymatic process in which only primary alcohols participate (in a 1 : 1 ratio with carboxylic acid). An unexpected finding is also disclosed where the simple additive, PhCF₃ (1 equiv. vs. substrate), appears to significantly extend the scope of usable acid/alcohol combinations. Taken together, several chemo- and bio-catalyzed 1-pot, multi-step reactions can now be performed in water.

Esterification in an aqueous micellar medium is catalyzed by a commercially available lipase in the absence of any co-factors.     

Nickel Nanoparticle Catalyzed Mono- and Di-Reductions of gem-Dibromocyclopropanes Under Mild,Aqueous Micellar Conditions

Mild mono- and di-hydrodehalogenative reductions of gem-dibromocyclopropanes are described, providing an easy and green approach towards the synthesis of cyclopropanes. The methodology utilizes 0.5–5 mol % TMPhen-nickel as the catalyst, which, when activated with a hydride source such as sodium borohydride, cleanly and selectively dehalogenates dibromocyclopropanes. Double reduction proceeds in a single operation at temperatures between 20–45 °C and at atmospheric pressure in an aqueous designer surfactant medium. At lower loading and either in the absence of ligand or in the presence of 2,2′-bipyridine, this new technology can also be used to gain access to not only monobrominated cyclopropanes, interesting building blocks for further use in synthesis, but also mono- or di-deuterated analogues. Taken together, this base-metal-catalyzed process provides access to cyclopropyl-containing products and is achieved under environmentally responsible conditions.     

Nickel Nanoparticle Catalyzed Mono‐ and Di‐Reductions of gem‐Dibromocyclopropanes Under Mild,Aqueous Micellar Conditions

Mild mono‐ and di‐hydrodehalogenative reductions of gem‐dibromocyclopropanes are described, providing an easy and green approach towards the synthesis of cyclopropanes. The methodology utilizes 0.5–5 mol % TMPhen‐nickel as the catalyst, which, when activated with a hydride source such as sodium borohydride, cleanly and selectively dehalogenates dibromocyclopropanes. Double reduction proceeds in a single operation at temperatures between 20–45 °C and at atmospheric pressure in an aqueous designer surfactant medium. At lower loading and either in the absence of ligand or in the presence of 2,2′‐bipyridine, this new technology can also be used to gain access to not only monobrominated cyclopropanes, interesting building blocks for further use in synthesis, but also mono‐ or di‐deuterated analogues. Taken together, this base‐metal‐catalyzed process provides access to cyclopropyl‐containing products and is achieved under environmentally responsible conditions.