A tandem Mannich addition–palladium catalyzed ring-closing route toward 4-substituted-3(2H)-furanones

• Jubi John,
• Eliza Târcoveanu,
• Peter G. Jones and
• Henning Hopf

Beilstein J. Org. Chem. 2014, 10, 1462–1470, doi:10.3762/bjoc.10.150

• . Keywords: aza-prostaglandin analogue; 3(2H)-furanone; Mannich addition; palladium catalysis; tandem reaction; Introduction Organic chemists welcome the introduction of facile tandem protocols because of the advantages of multiple bond formation in one-pot processes, which in turn makes the process

• commenced our investigations with the reaction of tosylimine 1a and ethyl 4-chloroacetoacetate (2a) in the presence of 5 mol % of Pd(PPh3)4 and 2.0 equivalents of Na2CO3, in dioxane at 50 °C for 10 hours. The reaction afforded 4-substituted-3(2H)-furanone 3 in 57% yield (Scheme 2). Interestingly, we could

• the yield of 3(2H)-furanone 3 by 23% by comparing the first control experiment and the reaction depicted in entry 8 of Table 1, thereby proving that palladium is catalyzing the reaction. With optimal conditions in hand (imine (1.0 equiv), 4-chloroacetoacetate (1.1 equiv), Pd2dba3·CHCl3 (5 mol %), dppe