Enantiomerically Pure 6-Substituted 2-Oxo-cyclohexanecarboxylates by Conjugate Addition of Cuprates to Asymmetric Shielded 2-Oxo-cyclohexenecarboxylates
摘要:
Asymmetric shielded 2-oxo-cyclohexenecarboxylates 6n and 6x were prepared by transesterification of 2-oxo-cyclohexanecarboxylate 2 with camphor derived concave alcohols In and Ix and by subsequent introduction of a double bond via phenylselenides. Diastereoselective conjugate addition of equimolar amounts of mixed cuprates at -78 degrees C and deprotection by methanolysis gave enantiomerically pure 6-substituted 2-oxo-cyclohexanecarboxylates 14-19 and ent-14-19, valuable as chiral building blocks in natural product synthesis.
Palladium-Catalyzed Intramolecular Hydroalkylation of Alkenyl- ?-Keto Esters, ?-Aryl Ketones, and Alkyl Ketones in the Presence of Me3SiCl or HCl
作者:Xiaoqing Han、Xiang Wang、Tao Pei、Ross A. Widenhoefer
DOI:10.1002/chem.200400459
日期:2004.12.17
palladium-catalyzed hydroalkylation, but rather served as a source of HCl, which presumably catalyzes enolization of the ketone. Identification of HCl as the active promoter of palladium-catalyzed hydroalkylation led to the development of an effective protocol for the hydroalkylation of alkyl 3-butenyl ketones that employed sub-stoichiometric amounts of 2, HCl, and CuCl2 in a sealed tube at 70 degrees C.
Achieving Vinylic Selectivity in Mizoroki-Heck Reaction of Cyclic Olefins
作者:Xiaojin Wu、Yunpeng Lu、Hajime Hirao、Jianrong Steve Zhou
DOI:10.1002/chem.201204427
日期:2013.5.3
In Heck reactions of cyclicolefins, the products usually have aryl groups that end up at the allylic and/or homoallylic position. We herein report new selectivity that adds aryl groups to the vinylic position. Cyclicolefins of various ring size worked well. The desired isomers were produced by palladium–hydride‐catalyzed isomerization of the initial products. Thus, a specific catalyst must be used
Unified Approach to the Chemoselective α-Functionalization of Amides with Heteroatom Nucleophiles
作者:Carlos R. Gonçalves、Miran Lemmerer、Christopher J. Teskey、Pauline Adler、Daniel Kaiser、Boris Maryasin、Leticia González、Nuno Maulide
DOI:10.1021/jacs.9b06956
日期:2019.11.20
electronegative than carbon requires an oxidation event. Herein we show that, by rendering the α-position of amides electrophilic through a mild and chemoselective umpolung transformation, a broad range of widely available oxygen, nitrogen, sulfur, and halogen nucleophiles can be used to generate α-functionalized amides. More than 60 examples are presented to establish the generality of this process, and calculations
1-N and 3-N ribosyl, allyl and (RS)-2',3'-dihydroxypropyl derivatives of 5,6-tetramethyleneuracil were prepared. Some of described compounds are inhibitors of enzymes involving in regulation of DNA synthesis.
C–C bond fragmentation by Grob/Eschenmoser reactions, applications in dendrimer synthesis
作者:Judith Hierold、David W. Lupton
DOI:10.1039/c3ob40800k
日期:——
C–C bond fragmentation of structurally diverse carbocycles has been applied to the divergent synthesis of dendrimers. The fragmentation has been paired to deprotection or thio-Michael reaction, allowing the preparation of a fourth generation dendrimer of narrow molecular weight distribution. Methodologies to increase water solubility have been examined using appended carboxylic acid or oligoether moieties