In the absence of transition-metal catalyst, Suzuki-Miyaura coupling reaction between aryl-and alkenylboronic acids and arylpropargylic bromides proceeded to give the corresponding acetylenic products selectively.
A cross-coupling reaction between aryl-and vinylboronic acids and various allylic bromides proceeded without the use of a transition-metal catalyst to give the corresponding allylated products in moderate to good yields. The use of an inorganic base (KF or Cs 2 CO 3 ) and a small amount of water is crucial in obtaining good performance in the present transition-metal-free reaction.The palladium-catalyzed cross-coupling reaction of allylic halides, 1 esters, 2 and alcohols 3 with organoboronic acids provides a magnificent tool for organic synthesis. With this method, we generally rely on the use of precious transition metals, such as Pd complexes, as the catalyst. 4 In 2005, Kabalka and co-workers reported that a crosscoupling reaction of secondary allylic alcohols with alkenylboron dihalides proceeded in the absence of a transition metal, in which typically stoichiometric n-BuLi was used as a base. 5 This work suggests the possibility of a metal-free process in the cross-coupling reaction of organoboron compounds, however, to the best of our knowledge, no related studies on the transition-metal-free crosscoupling reaction of organoboron compounds with allylic halides have not been reported. 6,7 Herein, we wish to report a Suzuki-Miyaura-type crosscoupling reaction of allylic bromides with aryl-and vinylboronic acids that proceeded under metal-free conditions (Scheme 1). Concurrently with our work, Scrivanti and co-workers reported a similar metal-free cross-coupling reaction, in which they used potassium carbonate as a base. However, the reaction reported in this work has a broader scope and generality than expected from their work. 8 Scheme 1 A transition-metal-free cross-coupling reaction of allylic bromides with organoboronic acids
Many studies have investigated the relationship between periodontal disease and the onset of peri-implantitis. It is important to devise practical measures for preventing the development of peri-implantitis in patients with periodontal disease if the success of implant treatment is to be secured. Here, we report the role of the superstructure in two cases of implant treatment in patients with severe periodontal disease. Both patients had severe periodontitis and underwent implant treatment after improving the state of the disease, thereby ensuring that the implant superstructure could be maintained. Both cases remained stable after implant treatment. The results indicate that proper periodontal treatment prior to implant treatment leads to long-term success. In addition, it is necessary to use an implant superstructure that reduces plaque accumulation in preventing peri-implantitis.
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