描述了 plakortone D 的第一次全合成,从而建立了海洋衍生的 plakortone 家族中最具生物活性成员的结构和绝对立体化学。空间拥挤的双环内酯核心是由 Pd(II) 诱导的羟基环化 - 羰基化 - 内酯化序列在烯二醇上产生的,其手性是通过 AD 技术安装的。侧链的连接也是使用 AD 方法构建的,是通过使用改进的 Julia 耦合实现的。所描述的方法能够以正确的(天然)立体化学系列获得其他 plakortones 和类似物。
Palladium(0)-Catalyzed Enantioselective <i>O</i>,<i>S</i>-Rearrangement of Racemic <i>O</i>-Allylic Thiocarbamates: A New Entry to Enantioenriched Allylic Sulfur Compounds
作者:Hans-Joachim Gais、Achim Böhme
DOI:10.1021/jo010668b
日期:2002.2.1
operation from the corresponding N-methyl S-allylic thiocarbamate through a palladium(0)-catalyzed substitution of iodobenzene in the presence of a base. The palladium(0)-catalyzed enantioselective rearrangement of O-allylic carbamates to S-allylic carbamates has been extended from the solution phase to the solid phase by using a methyl thioisocyanate polystyrene resin. In the case investigated the enantioselectivity
In situ 1H-PHIP-NMR studies of the stereoselective hydrogenation of alkynes to ( E)-alkenes catalyzed by a homogeneous [Cp*Ru]+ catalyst
作者:Dana Schleyer、Heiko G. Niessen、Joachim Bargon
DOI:10.1039/b007201j
日期:——
The hydrogenation of internal alkynes using a [Cp*Ru(alkene)]+ complex leads to the formation of (E)-alkenes. This ruthenium complex represents one of the few homogeneous catalysts that trans-hydrogenate internal alkynes directly and stereoselectively. We have studied its stereoselectivity by in situ PHIP-NMR spectroscopy (PHIP = para-hydrogen
induced polarization). With this method the initially formed products can be identified and characterized even at very low concentrations and low conversions. Furthermore, their subsequent fate can be evaluated with high sensitivity and with time resolution. Different alkyne substrates were used to demonstrate the universal applicability of this catalyst. The catalyst is not active in combination with terminal alkynes, however, possibly due to the formation of a rather stable vinylidene complex. A mechanism
proceeding ia a binuclear complex is proposed to explain the formation of the (E)-alkenes.
Ni-Catalyzed Reductive Allylation of Unactivated Alkyl Halides with Allylic Carbonates
作者:Yijing Dai、Fan Wu、Zhenhua Zang、Hengzhi You、Hegui Gong
DOI:10.1002/chem.201102984
日期:2012.1.16
catalytic Ni species in the presence of an environmentally benign Zn reductant, delivering allylated alkanes (see scheme). This unprecedented approach allowed a variety of unactivated alkylhalides and substituted allyliccarbonates to regioselectively afford E‐alkenes in good to excellent yields.
Total synthesis of levetiracetam via a one-pot dehydration/rearrangement of (R,E)-hept-4-en-3-ol carbamate to the corresponding allylamine derivative is reported.
Pd‐Catalyzed Asymmetric N‐Allylation of Amino Acid Esters with Exceptional Levels of Catalyst Control: Stereo‐Divergent Synthesis of ProM‐15 and Related Bicyclic Dipeptide Mimetics
powerful method for the stereo-controlled Pd-catalyzed N-allylation of aminoacid esters is reported, as a previously largely unsolved synthetic challenge. Employing a new class of tartaric acid-derived C2 -symmetric chiral diphosphane ligands the developed asymmetric amination protocol allows the conversion of various aminoacid esters to the N-allylated products with highest levels of enantio- or