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Multi-substituted dihydrofurans are valuable intermediates for the synthesis of natural products and pharmaceuticals. Considerable attention has been focused on the development of efficient and regioselective methods for their preparation. Using K2CO3 as a base, with the reaction of fur-2-oylmethyltriphenylarsonium bromide 1 and ethyl 2-acetyl-3-arylacrylate 2 in tetrahydrofuran at room temperature, we found an efficient protocol was achieved to synthesize trans-3-aryl-4-carbethoxy-2,3-dihydro-2-fur-2'-oyl-5-methylfurans 3 in good yield with high stereoselectivity. The structure of compound 3 was confirmed by IR, ^1H NMR, MS and HRMS. The mechanism for the formation of 3 was proposed. 相似文献
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用密度泛函理论研究了CF3SO3CF2CF3 F^-的碳氧键断裂反应的机理。首先,用DFT方法优化了反应物、中间体、过渡态、产物的平衡构型,分析了碳氧键断裂反应的势能面变化,发现在SN2反应机理中,除了S-O断裂SN2反应外,引起C-O键断裂的同面进攻也是一个可能的反应途径。理论计算表明,最终反应的产物是受热力学控制的,S-O键的断裂绝对地优于C-O的断裂。因此,C-O断裂的同面机理虽然是可能的,但却难以被实验观察到,本文还讨论了端基-CF3在同面SN2反应中的邻位效应,以及基组对这个效应的影响。 相似文献
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二氟甲磺酸(1)在室温下即可和五氧化二磷作用,但和全氟烷烃磺酸不同,它并不生成相应的磺酸酐。脱水后进一步消除二氧化硫产生二氟卡宾,二氟卡宾再插入二氟甲磺酸得到二氟甲磺酸二氟甲酯(2)。若有其它全氟烷基磺酸或全氟烷基羧酸存在时,也可得到相应的全氟烷基磺酸二氟甲酯(4)或全氟烷基羧酸二氟甲酯(6)。用三氯氧磷或二氯亚砜代替五氧化二磷和1作用,也得到类似的结果。对二氟卡宾生成的可能机理进行了讨论。 相似文献
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FO_2SCF_2CO_2CH_3(1)和许多亲核试剂作用时很容易发生脱羧甲基分解反应。例如X~-(Cl~-,Br~-,I~-)CNS~-,Et_3N,C_5H_5N等都可以进攻其甲基碳,接着消去CO_2,SO_2和F~-而产生:CF_2。在非水有机溶剂中,脱羧后极快地同时消去SO_2,F~-形成:CF_2;但在含水有机溶剂中,则先形成中间体FO_2SCF_2~-,它可被质子捕获生成HCF_2SO_2F(2)。大部分仍继续消除SO_2和F~-产生:CF_2。烷氧阴离子不能类似地将1分解,而是进攻1的硫原子得到相应的磺酸酯CH_3O_2CCF_2SO_2—Z(10)(Z=OCH_2CF_2CF_2H,OC_6H_5)。在无溶剂情况下,Et_2NH也能使1分解而形成:CF_2,还伴有少量进攻羧基碳的产物FO_2SCF_2CONEt_2(11)。 相似文献
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Halogenation of the potassium or silver salts of bis(trifluoromethanesulfonyl)methane (CF3SO2)2CH2 and its cyclo analogues 1 with N-fluoro-bis(trifluoromethanesulfonyl)imine [(CF3SO2)2-NF], chlorine or bromine gave good yields of the corresponding α-halo disulfone (CF3SO2)2CHX and cyclo analogues 9, 10. The chemical transformation of these fluorinated α-halo-disulfones are described. 相似文献
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二氟甲磺酸二氟甲酯HCF_2SO_3CF_2H(1)和三氟甲磺酸二氟甲酯CF_3SO_3CF_2H(2)相比,在亲核反应中显出较大的差异.由于α-氢的存在,在一定程度上影响了它和亲核试剂的反应,如KF和2作用时得到HCF_3.但与1反应却只进攻其硫原子,得到HCF_2SO_2F(3).而KI与1作用时既可进攻硫又可进攻其烷氧基碳.其它亲核试剂如RCO_2~-、ArS~-等却只进攻1的硫原子.碱性较强的苯酚钠和1作用时除分别进攻硫和碳外,还可攫取其氢原子而产生二氟卡宾.若反应温度较低时,则仅攫取其二氟甲基的氢;若于90℃反应,则还可同时攫取二氟甲氧基的氢.碱性更强的乙醇钠与1反应时则是以攫氢为主. 相似文献
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溴化(a-噻吩甲酰基)甲基三苯鉮1与3-取代苯甲叉基-2,4-戊二酮 2以碳酸钾为碱,在苯中55℃条件下反应,可以较好的收率、高立体选择性地生成反-2-(a-噻吩甲酰基)-3-取代苯基-4-乙氧羰基-5-甲基-2,3-二氢呋喃3。产物结构均经波谱予以确定。本文还提出了生成产物的可能机理。 相似文献
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A series of novel Meldrum's acid C60 derivatives were prepared in moderate yields from a convenient one-pot reaction of C60, the Meldrum's acid derivatives, 12 and 1,8-diazabicyclo-[5,4,0]-undec-7-ene (DBU) in toluene at room temperature under nitrogen atmosphere. All the new compounds were fully characterized by the spectral data and elemental analysis. A carbene intermediate mechanism was proposed for this reaction. 相似文献
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