Rayabarapu Dinesh Kumar, Chang Hong-Tai, Cheng Chien-Hong
Department of Chemistry, Tsing Hua University, Hsinchu 300, Taiwan.
Chemistry. 2004 Jun 21;10(12):2991-6. doi: 10.1002/chem.200305740.
The reaction of o-bromobenzoate (1 b) with benzaldehyde (2 a) in the presence of [NiBr(2)(dppe)] (dppe=1,2-bis(diphenylphosphino)ethane) and zinc powder in THF (24 hours, reflux temperature), afforded 3-phenyl-3H-isobenzofuran-1-one (3 a) in an 86 % yield. Similarly, o-iodobenzoate reacts with 2 a to give 3 a, but in a lower yield (50 %). A series of substituted aromatic and aliphatic aldehydes (2 b, 4-MeC(6)H(4)CHO; 2 c, 4-MeOC(6)H(4)CHO; 2 d, 3-MeOC(6)H(4)CHO; 2 e, 2-MeOC(6)H(4)CHO; 2 f, 4-CNC(6)H(4)CHO; 2 g, 4-(Me)(3)CC(6)H(4)CHO; 2 h, 4-C(6)H(5)C(6)H(4)CHO; 2 i, 4-ClC(6)H(4)CHO; 2 j, 4-CF(3)C(6)H(4)CHO; 2 k, CH(3)(CH(2))(5)CHO; 2 l, CH(3)(CH(2))(2)CHO) also underwent cyclization with o-bromobenzoate (1 b) producing the corresponding phthalide derivatives in moderate to excellent yields and with high chemoselectivity. Like 1 b, methyl 2-bromo-4,5-dimethoxybenzoate (1 c) reacts with tolualdehyde (2 b) to give the corresponding substituted phthalide 3 m in a 71 % yield. The methodology can be further applied to the synthesis of six-membered lactones. The reaction of methyl 2-(2-bromophenyl)acetate (1 d) with benzaldehyde under similar reaction conditions afforded six-membered lactone 3 o in a 68 % yield. A possible catalytic mechanism for this cyclization is also proposed.
在四氢呋喃中，邻溴苯甲酸酯（1b）与苯甲醛（2a）在[NiBr₂(dppe)]（dppe = 1,2 - 双（二苯基膦基）乙烷）和锌粉存在下反应（24小时，回流温度），以86%的产率得到3 - 苯基 - 3H - 异苯并呋喃 - 1 - 酮（3a）。类似地，邻碘苯甲酸酯与2a反应生成3a，但产率较低（50%）。一系列取代的芳香族和脂肪族醛（2b，4 - MeC₆H₄CHO；2c，4 - MeOC₆H₄CHO；2d，3 - MeOC₆H₄CHO；2e，2 - MeOC₆H₄CHO；2f，4 - CNC₆H₄CHO；2g，4 - (Me)₃CC₆H₄CHO；2h，4 - C₆H₅C₆H₄CHO；2i，4 - ClC₆H₄CHO；2j，4 - CF₃C₆H₄CHO；2k，CH₃(CH₂)₅CHO；2l，CH₃(CH₂)₂CHO）也与邻溴苯甲酸酯（1b）发生环化反应，以中等至优异的产率和高化学选择性生成相应的苯酞衍生物。与1b一样，2 - 溴 - 4,5 - 二甲氧基苯甲酸甲酯（1c）与甲苯醛（2b）反应，以71%的产率得到相应的取代苯酞3m。该方法可进一步应用于六元内酯的合成。在类似反应条件下，2 - （2 - 溴苯基）乙酸甲酯（1d）与苯甲醛反应，以68%的产率得到六元内酯3o。还提出了这种环化反应可能的催化机理。
