Silver-Catalyzed Radical Phosphonofluorination of Unactivated Alkenes
摘要:
We report herein a mild and catalytic phosphonofluorination of unactivated alkenes. With catalysis by AgNO3, the condensation of various unactivated alkenes with diethyl phosphite and Selectfluor reagent in CH2Cl2/H2O/HOAc at 40 degrees C led to the efficient synthesis of beta-fluorinated alkylphosphonates with good stereoselectivity and wide functional group compatibility. A mechanism involving silver-catalyzed oxidative generation of phosphonyl radicals and silver-assisted fluorine atom transfer is proposed.
Enantioselective Organocatalyzed Bromolactonizations: Applications in Natural Product Synthesis
作者:Marius Aursnes、Jørn E. Tungen、Trond V. Hansen
DOI:10.1021/acs.joc.6b01375
日期:2016.9.16
The best catalyst enabled the cyclization of several 5-arylhex-5-enoic acids into the corresponding bromolactones with up to 96% ee and in high to excellent chemical yields. The reported catalysts are prepared in a straightforward manner in two steps from dimethyl squarate. The utility of the developed protocol was demonstrated in highly enantioselective syntheses of the sesquiterpenoids (−)-gossoronol
Achiral Counterion Control of Enantioselectivity in a Brønsted Acid-Catalyzed Iodolactonization
作者:Mark C. Dobish、Jeffrey N. Johnston
DOI:10.1021/ja301858r
日期:2012.4.11
Highly enantioselective halolactonizations have been developed that employ a chiral proton catalyst-N-iodosuccinimide (NIS) reagent system in which the Brønsted acid is used at catalyst loadings as low as 1 mol %. An approach that modulates the achiral counterion (equimolar to the neutral chiral ligand-proton complex present at low catalyst loadings) to optimize the enantioselection is documented for
The apple never falls far from the tree: S‐alkylthiocarbamate 1 (see scheme, NBP=N‐bromophthalimide) was prepared in high yield through a synthetic sequence involving a Newman–Kwart rearrangement of the corresponding O‐alkylthiocarbamates. Compound 1 was used to catalyze bromolactonization, thus providing enantioenriched δ‐lactones in excellent yield and enantioselectivity.
作者:Jørn E. Tungen、Renate Kristianslund、Anders Vik、Trond V. Hansen
DOI:10.1021/acs.joc.9b01294
日期:2019.9.20
A highly efficient and regioselective bromolactonization protocol is reported. The quantitative formation of synthetically versatile bromolactones occurs in the presence of only 0.1 mol % of an organoselenium compound, coined DECAD herein, within 90 min. DECAD is conveniently prepared on multigram scale from cheap racemic camphor. The presented protocol was easy to scale up and performed equally well
Binding the anion: A highly enantioselectiveiodolactonization of 5‐hexenoic acids has been achieved using a tertiary aminourea‐catalyst (see scheme). The use of catalytic iodine in this process is critical to enhancing both the reactivity and enantioselectivity of the stoichiometric I+ source. The mechanism is proposed to involve binding of an iodonium imidate intermediate by the H‐bond donor catalyst
结合阴离子:使用叔氨基脲催化剂实现了 5-己烯酸的高度对映选择性碘内酯化(参见方案)。在该过程中使用催化碘对于提高化学计量 I +源的反应性和对映选择性至关重要。该机制被认为涉及通过氢键供体催化剂结合亚胺酸碘鎓中间体。