activation. A highly regioselective synthetic method based on the domino Diels–Alder/retro-Diels–Alder reaction (DA/RDA) of 1,3-dienic δ-sultones with alkynes provides substituted m-terphenyls by elimination of SO3. A variety of δ-sultones and alkynes were examined to determine the scope of the reaction. The de novo synthesized aromatic products were obtained using thermal, microwave, and high-pressure
substituted arenes using vinylsulfoxoniumylides and ynones. The addition of ynone at the γ-position of vinylsulfoxoniumylides leads to dienyl sulfoxoniumylide that can undergo selective annulation under different conditions to give m-terphenyls and parabens. Moreover, control experiments and quantum chemical calculations reveal two distinct reaction mechanisms for both annulations.
Transition metal-catalyzed dehydrogenation is a clean oxidation method requiring no additional oxidants. We have accomplished a heterogeneous Pd/C-catalyzed aqueous dehydrogenation of 1,4-cyclohexadienes and cyclohexenes to give the corresponding highly-functionalized arenes. Furthermore, various arenes could be efficiently constructed in a one-pot manner via a Diels–Alder reaction and the following
N-Heterocyclic Carbene-Catalyzed Annulation of Ylides with Ynals: Direct Access to α-Pyrones
作者:Ming Lang、Qianfa Jia、Jian Wang
DOI:10.1002/asia.201800595
日期:2018.9.4
We herein report an N‐HeterocyclicCarbene (NHC)‐catalyzed annulation of ylides with ynals that provides an efficient protocol to make 4,6‐disubstituted α‐pyrones. This method affords a variety of α‐pyrones in good to high yields as well as broad substrate scope and good functional group tolerance.