In Situ Preparation of a Highly Active N-Heterocyclic Carbene-Coordinated Olefin Metathesis Catalyst
作者:John P. Morgan、Robert H. Grubbs
DOI:10.1021/ol0063510
日期:2000.10.1
active N-heterocyclic carbene-coordinatedcatalysts may be synthesized and used in situ, without requiring prior isolation of the catalyst. Activation of this in situ catalyst with ethereal HCl dramatically reduces the reaction times required for high conversions. A variety of alpha,beta-unsaturated carbonyl-containing substrates participate readily in cross and ring-closing metathesis reactions using this
Cyclizations in the Addition of Alkylmercury Halides to Dienes and Enynes
作者:Glen A. Russell、Chaozhong Li、Ping Chen
DOI:10.1021/ja9601898
日期:1996.1.1
or CH2CHC(O)OC(Me)2CHCH2. The radicals t-BuCH2CH•C(O)C(Me)2(CH2)nCHCH2 cyclize mainly in the 6-endo mode for n = 1 and more rapidly in the 6-exo mode for n = 2, while the radicals t-BuCH2CH•C(O)OC(Me)2(CH2)nCHCH2 cyclize only in the exo mode for n = 0 or 1 but with a faster rate for 5-exo-cyclization. Gem-dimethyl substitution adjacent to the alkyl oxygen accelerates the 5-exo-cyclization of the ester
将叔丁基卤化汞光刺激加成到 1,6-二烯和烯炔,包括 (CH2CHCH2)2X,其中 X = CH2、C(COEt)2、O 或 NCH2CHCH2,形成由 5-外环化产生的初级烷基卤化汞加合物自由基,t-BuCH2CH•CH2XCH2CHCH2。这些自由基过程的动力学链长度很低,在 Me2SO 中 35 °C 时的范围为 3-7。在光刺激下将 t-BuHgI 添加到 CH2CHP(O)(OR)OCH2CHCH2(R = H 或烯丙基)、CH2CHC(O)N(R)CH2CHCH2(R = Me、Ph 或 CH2CHCH2) 或 CH2CHC(O)OC(Me)2CHCH2。基团 t-BuCH2CH•C(O)C(Me)2(CH2)nCHCH2 在 n = 1 时主要以 6-endo 模式环化,在 n = 2 时以 6-exo 模式更快地环化,而基团 t-BuCH2CH•C(O)OC(Me)2(CH2)nCHCH2
Ruthenium Carbene Complexes with <i>N</i>,<i>N</i>‘-Bis(mesityl)imidazol-2-ylidene Ligands: RCM Catalysts of Extended Scope
作者:Alois Fürstner、Oliver R. Thiel、Lutz Ackermann、Hans-Jörg Schanz、Steven P. Nolan
DOI:10.1021/jo9918504
日期:2000.4.1
The ruthenium carbene complexes 3a,b bearing imidazol-2-ylidene ligands constitute excellent precatalysts for ring-closing metathesis (RCM) reactions allowing the formation of tri- and tetrasubstituted cycloalkenes. They also apply to annulations that are beyond the scope of the standard Grubbs carbene 1 as well as to ring-closing reactions of acrylic acid derivatives even if the resulting alpha,beta-unsaturated lactones (or lactams) are tri- or tetrasubstituted. The reactivity of 3a was found to be highly dependent on the reaction medium: particularly high reaction rates are observed in toluene, although this solvent also leads to an increased tendency of the catalyst to isomerize the double bonds of the substrates.
Volatiles from the tropical ascomycete <i>Daldinia clavata</i> (Hypoxylaceae, Xylariales)
作者:Tao Wang、Kathrin I Mohr、Marc Stadler、Jeroen S Dickschat
DOI:10.3762/bjoc.14.9
日期:——
apparatus and analysed by GC-MS. A few compounds were readily identified by comparison of measured to library mass spectra and of retention indices to published data, while for other compounds a synthesis of references was required. For one of the main compounds, 5-hydroxy-4,6-dimethyloctan-3-one, the relative and absolute configuration was determined by synthesis of all eight stereoisomers and gas chromatographic