Cascade Synthesis in Water: Michael Addition/Hemiketalization/Retro-Claisen Fragmentation Catalyzed by CatAnionic Vesicular Nanoreactor from Dithiocarbamate.

Abstract

N,N-didodecylammonium N,N-didodecyldithiocarbamate (AmDTC-C12C12) underwent self-assembly to form a CatAnionic vesicular nanoreactor in water. AmDTC-C12C12 can be readily prepared by condensation between N,N-didodecylamine and carbon disulfide. Previously, the cascade Michael addition/hemiketalization/retro-Claisen fragmentation was reported, but it required petroleum-based organic solvents as reaction media. Herein, the application of AmDTC-C12C12 in aqueous cascade synthesis is investigated. Initially, we explored the catalytic activity of AmDTC-C12C12 (10 mol%) in the synthesis of 4H-chromene through a double-cascade Michael addition/hemiketalization. The reaction occurred in water at room temperature using 2-hydroxy-trans-b-nitrostyrene as Michael acceptor and acetylacetone as Michael donor yielding 2-chromanol intermediates. Subsequent acidic dehydration of 2-chromanols produced 4H-chromenes with moderate yields (34-60%) and phenyl acetates of g-nitro ketone as co-products (13-27%), deriving from retro-Claisen fragmentation. Surprisingly, using Michael donors with aromatic moieties on the 1,3-dicarbonyls resulted in spontaneous triple-cascade Michael addition/hemiketalization/retro-Claisen fragmentation in water, without the need for acidic dehydration. The g-nitro ketones were obtained as sole products, with no detection of 4H-chromenes, in moderate to high yields (31-84%) for symmetrical 1,3-dicarbonyl containing two aromatic groups. Unsymmetrical 1,3-dicarbonyl bearing aromatic/aliphatic or aromatic/aromatic groups afforded g-nitro ketones in favorable yields (73-97%).