Manandhar Sudha, Singh Rajendra P, Eggers Gary V, Shreeve Jean'ne M
Department of Chemistry, University of Idaho, Moscow, Idaho 83844-2343, USA.
J Org Chem. 2002 Sep 6;67(18):6415-20. doi: 10.1021/jo0258554.
Interactions of various fluorinated and nonfluorinated alcohols with trans-stilbene in the presence of electrophilic reagents were studied. Under neat conditions, reactions of trans-stilbene (1) with fluorinated alcohols, R(f)OH (R(f) = CF3CH2-, CFH2CH2-, CF3CF2CH2-, CF2H(CF2)3CH2-, (CF3)2CH-, (CF3)3C- (2a-f) in the presence of an electrophilic reagent, 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) or N,N-difluoro-2,2'-bipyridinium bis(tetrafluoroborate) (MEC-31), gave alpha-keto ethers (3a-f) and benzil (4) in good to moderate yields. alpha-Keto ether and benzil formation was very much dependent on the reaction time, the degree of fluorination of the alcohols, and whether a solvent such as CH3CN, DMF or DMA was utilized. In solution, alpha-keto ethers and benzil did not form. Interestingly, under neat conditions, nonfluorinated alcohols, ROH (R = CH3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-, CH3CH2CH2CH2CH2CH2-) (5g-k) did not react with trans-stilbene in the presence of MEC-31 but gave 6,6'-dialkoxy-2,2'-bipyridines (6g-k), regioselectively, in excellent isolated yields. On the other hand, fluorinated alcohols did not react with MEC-31. Reaction of MEC-31 with an excess of diethylene glycol (7) gave the bipyridine derivative (8) in 88% isolated yield. Reaction of 8 either with diethylaminosulfur trifluoride (DAST) or bis(2-methoxyethyl)aminosulfur trifluoride (Deoxofluor) readily produced the corresponding difluoro derivative (9) in 85% isolated yield. All new compounds have been characterized by spectroscopic and elemental analysis.
研究了在亲电试剂存在下各种氟化醇和非氟化醇与反式芪的相互作用。在纯态条件下，反式芪（1）与氟化醇R(f)OH（R(f)=CF3CH2-、CFH2CH2-、CF3CF2CH2-、CF2H(CF2)3CH2-、(CF3)2CH-、(CF3)3C-（2a - f））在亲电试剂1-(氯甲基)-4-氟-1,4-二氮杂双环[2.2.2]辛烷双（四氟硼酸盐）（Selectfluor）或N,N-二氟-2,2'-联吡啶鎓双（四氟硼酸盐）（MEC - 31）存在下反应，以良好至中等产率得到α-酮醚（3a - f）和联苯甲酰（4）。α-酮醚和联苯甲酰的形成非常依赖于反应时间、醇的氟化程度以及是否使用诸如CH3CN、DMF或DMA等溶剂。在溶液中，不会形成α-酮醚和联苯甲酰。有趣的是，在纯态条件下，非氟化醇R(f)OH（R = CH3-、CH3CH2-、CH3CH2CH2-、CH3CH2CH2CH2-、CH3CH2CH2CH2CH2CH2-（5g - k））在MEC - 31存在下不与反式芪反应，但选择性地以优异的分离产率得到6,6'-二烷氧基-2,2'-联吡啶（6g - k）。另一方面，氟化醇不与MEC - 31反应。MEC - 31与过量的二甘醇（7）反应，以88%的分离产率得到联吡啶衍生物（8）。8与二乙氨基三氟化硫（DAST）或双（2 - 甲氧基乙基）氨基三氟化硫（Deoxofluor）反应，很容易以85%的分离产率得到相应的二氟衍生物（9）。所有新化合物均通过光谱和元素分析进行了表征。
