addition of nucleophiles to α-methyl-β-methylene carbonyl compounds combined with the hydromagnesiation reactions of 2-alkyl-substituted 1,3-dienes affords a practical, efficient stereo- and regio-controlledaldolsynthesis.
The competitive and non-competitive hydroformylation of conjugated dienes starting with tetrarhodium dodecacarbonyl. An in-situ high-pressure infrared spectroscopic study
作者:Guowei Liu、Marc Garland
DOI:10.1016/s0022-328x(00)00369-7
日期:2000.8
known that the liquid-phase homogeneous unmodified rhodium catalysed hydroformylation of alkenes is poisoned by the presence of trace quantities of conjugateddienes. Nevertheless, some hydroformylation of conjugateddienes is possible with unmodified rhodium, and this reaction is in general slower than alkene hydroformylations at comparable reaction conditions. In the present contribution, we examined
众所周知,液相的均相未改性铑催化的烯烃加氢甲酰化会因存在痕量的共轭二烯而中毒。然而,在未改性的铑条件下,共轭二烯的加氢甲酰化反应还是可能的,而且在可比的反应条件下,该反应通常比烯烃的加氢甲酰化反应慢。在本贡献中,我们检查(A)烯烃的痕量的存在下催化性能的共轭二烯的杂质和(B)的各种使用铑二烯烃的催化行为4(CO)12在ñ -己烷溶剂中在293度在1.0-4.0 MPa CO和0.5-2.0 MPa H 2下。分析方法是原位高压红外光谱法。观察到(I)在有毒烯烃的加氢甲酰化中,大多数铑在这种竞争情况下与痕量的共轭二烯发生反应,而不与烯烃发生反应;以及(II)各种二烯加氢甲酰化的金属羰基光谱非常相似。在共轭二烯的加氢甲酰化中观察到的一次吸光度最大值出现在大约2109、2091、2087、2064、2049、2037、2030、2020、2012、1999和1990 cm -1。给出铑的已知化学
Copper-Catalyzed Rearrangement of Vinyl Oxiranes
作者:Lindsay A. Batory、Christine E. McInnis、Jon T. Njardarson
DOI:10.1021/ja067073o
日期:2006.12.1
A novel copper-catalyzed vinyl oxirane ring expansion protocol has been developed. A wide range of vinyl oxiranes can be rearranged to 2,5-dihydrofurans in excellent yields in the presence of electrophilic copper(II) acetylacetonate catalysts. Regioisomeric vinyl oxiranes can be converted to a single dihydrofuran product using these conditions. This method uses low catalyst loadings (0.5-5 mol %), has good tolerance of substitution patterns, and can be done in the absence of solvent.
Prevost, Bulletin de la Societe Chimique de France, 1944, vol. <5>11, p. 223
作者:Prevost
DOI:——
日期:——
Visible light induced reactions of nitrogen dioxide with conjugated dienes in a low-temperature argon matrix
Visible light induced oxygen atom transfer from NO2 to conjugated dienes has been investigated in a low-temperature Ar matrix, where the dienes are 1,3-butadiene (BD), 2-methyl-1,3-butadiene (isoprene), and 2,3-dimethyl-1,3-butadiene (DMB). In each diene/NO2/Ar system, the corresponding nitrite radical, oxirane, aldehyde, and NO were obtained as the photochemical reaction products. The reactions are initiated by the formation of undetectable short-lived oxirane biradical and NO due to visible light induced 0 atom transfer from NO2 to the conjugated dienes. (1) The recombination of oxirane biradicals and neighboring NO gives the nitrite radicals as the photochemical intermediate. (2) The ring closure of the biradicals leads to the formation of oxiranes. (3) The intramolecular H atom transfer of biradicals leads to the formation of aldehydes. The visible photolysis of the nitrite radicals gives rise to oxirane, aldehyde, and NO. The reaction rates are derived by measuring the absorbance changes of the products upon the 582-nm irradiation. The methyl substituent effect on the reactivity is discussed.