Acetylacetone 2a

We began our research by treating chalcone 1a (??) with acetylacetone 2a (??) in the presence of morpholine as the base (??) in CH3CN at 80 ºC for 12 h. The reaction was monitored by TLC until the disappearance of the starting material and the formation of 1-(5-benzoyl-2-methyl-4-phenyl-2,3-dihydrofuran-3-yl)ethanone 3a. this reaction mixture, containing the 2,3-dihydrofuran 3a generated in situ, was treated with sulfur element (??) in the presence of base of morpholine (??) at 80°C and the desired thiophene 4a was obtained in ?? % yield, after 5 h (Table 1). In order to find out the best reaction conditions for the synthesis of thiophene 4a, the reaction of 1a (??mmol) and 2a (?? mmol) have been screened by various parameters such as type and amount of base, reaction solvents and reaction temperatur.
We were employed (used from) other organic or inorganic bases such as piperidine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), NEt3, KHCO3, NaHCO3, K2CO3 and Na2CO3, in instead of morpholine for the first step of reaction, followed by ??equivalent of morpholine in acetonitrile (entries 2-8). We observed the best yield of thiophene 4a was obtained, when NEt3 used as the base of the first step of reaction (entry 4). Thus, we chose NEt3 as the suitable base for the first step of reaction (for this step).