Synthesis of Hypervalent Organobromanes and Threi Synthetic Organic Reactions

(1)首次报道了高价1-炔基(芳基)-λ^3-溴的合成、结构和反应。在BF_3催化下，对三氟甲基苯基(二氟)-λ^3-溴与1-炔基(三甲基)锡烷在-78℃的二氯甲烷中与溴(III)发生配体交换反应，高产率地合成了1-炔基(芳基)-λ^3-溴。三甲基(三甲基硅乙炔)锡烷选择性地合成了硅乙炔-λ^3-溴。比较了炔基溴与炔基-λ^3-碘烷的&lt；13&gt；cCNMR化学位移，并用自旋轨道诱导的重原子效应对其进行了解释。通过对其冠醚络合物的单晶X-射线分析，确定了叔丁乙基溴的结构。1-炔基(芳基)-λ^3-溴作为高度缺电子的迈克尔受体，与磺酸盐阴离子发生串联迈克尔-卡宾重排反应生成1-炔基磺酸盐。(2)首次报道了高价β-卤代烯基-λ^3-溴的合成、分离和表征。用BF_3-I-Pr_2O活化的对三氟甲基苯基(二氟)-λ^3-溴与末端炔反应，以马尔可尼可夫方式使三键发生氟-λ^3-溴代反应，以较好的产率得到(E)-β-氟烯基-λ^3-溴。根据取代基的不同，5-氯-1-戊炔发生λ、3-溴代-氯变换-氟化或λ^3-溴代-氯变换-烷基变换-氟化反应，高产率地得到(E)-β-氯烯基-λ^3-溴。β-氯烯基-λ^3-溴在分子中含有三种卤素原子F、Cl和Br.

(1)Reported here for the first time are the synthesis, structure, and reaction of hypervalent 1-alkynyl(aryl)-λ^3-bromanes. BF_3-catalyzed ligand exchange on bromine(III) of p-trifluoromethylphenyl(difluoro)-λ^3-bromane with 1-alkynyl(trimethyl)stannanes in dichloromethane at -78℃ afforded 1-alkynyl(aryl)-λ^3-bromanes in good yields. Trimethyl(trimethylsilylethynyl)stannane gave silylethynyl-λ^3-bromane selectively. ^<13>C NMR chemical shifts of acetylenic carbon atoms of alkynylbromanes are compared with those of alkynyl-λ^3-iodanes and explained in terms of the spin-orbit-induced heavy atom effects. The structure of tert-butylethynylbromane was established by a single crystal X-ray analysis of its crown ether complex. The 1-alkynyl(aryl)-λ^3-bromanes serve as highly electron deficient Michael acceptors and undergo tandem Michael-carbene rearrangements by the reaction with sulfonate anions yielding 1-alkynyl sulfonates.(2)Reported here for the first time are the synthesis, isolation, and characterization of hypervalent β-haloalkenyl-λ^3-bromanes. Exposure of terminal alkynes to p-trifluoromethylphenyl(difluoro)-λ^3-bromane activated by BF_3-i-Pr_2O resulted in fluoro-λ^3-bromanation of the triple bonds in a Markownikoff fashion yielding (E)-β-fluoroalkenyl-λ^3-bromanes stereoselectively in good yields. 5-Chloro-1-pentynes undergo domino λ^3-bromanation-chlorine shift-fluorination or λ^3-bromanation-chlorine shift-alkyl shift-fluorination reaction depending on the substituents and afford (E)-β-chloroalkenyl-λ^3-bromanes stereoselectively in high yields. The β-chloroalkenyl-λ^3-bromanes contain three kinds of halogen atoms F,Cl, and Br in the molecule.