Here, we report insights into the new recyclable catalyst 1, (DMAP·saccharin). The DMAP·saccharin-catalysed acylation of alcohols has been successfully carried out more than 8 times. Only 1 mol% of catalyst 1 efficiently promotes acylation with almost equimolar amounts of acid anhydrides, under both base-free and solvent-free conditions.
The reaction of allyl palladium(II) chloride dimer and 4,4¢-bis(R f CH 2 OCH 2 )-2,2¢-bpy, 1a-b, in the presence of AgOT f resulted in the synthesis of cationic palladium complex, [Pd(h 3 -allyl)(4,4¢-bis-(R f CH 2 OCH 2 )-2,2¢-bpy)](OT f ), 2a-b where R f = C 9 F 19 (a), C 10 F 21 (b), respectively. The reaction of [PdCl 2 (CH 3 CN)] or K 2 PdCl 4 with 1b, gave rise to the synthesis of [PdCl 2 (4,4¢-bis-(C 10 F 21 CH 2 OCH 2 )-2,2¢-bpy)], 3b. The quantitatively determined solubility curves of 2a-b and 3b in DMF indicated dramatic increase of solubility for 2a-b and 3b from -40 to 90°C. The catalyst-recoverable Pd-catalyzed Heck/ Sonogashira reactions were successfully achieved in DMF with microwave-assistance. The cationic Pd-catalyzed Heck arylation of methyl acrylate was selected to demonstrate the feasibility of recycling 2a-b using DMF as a solvent under microwave-assisted thermomorphic conditions. At the end of each cycle, the product mixtures were cooled, and then the catalysts were recovered by decantation. The Heck arylation catalyzed by 2b under microwave-assisted mode exhibited good recycling results favoring the trans product. To our knowledge, this is the first example of cationic Pd-catalyzed Heck arylation under microwave-assisted thermomorphic conditions. Additionally, recoverable 3b-catalyzed Sonogashira reactions were also achieved successfully in DMF. The reactions under microwave-assistance gave much better results in yield and in efficiency than that under conventional thermal heating.
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